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Abstract 2021

Rivista Mineralogica Italiana > Abstract Articoli
Abstract ITALIAN MINERALOGICAL MAGAZINE
nr. 1-2021
MINERALS OF THE
“HISTORIC” QUARRIES OF TRASQUERA
VAL DIVEDRO- CAIRASCA (VB)


This  article  describes  a  number  of characteristic minerals, found in the abandoned  quarries  of  Antigorio orthogneiss,  locally  known  as  “serizzo” located in the municipality of Trasquera, in Divedro Valley. These quarries were exploited until the early 1970s. During several visits, made in the 1990 , these quarries have pro- vided good mineralogical specimens of “apatite”, anatase, brookite, epidote, heulandite-Ca, stilbite-Ca and titanite.  Although  less  frequently than in the past, it is still possible to find good specimens today.

GYPSUM CRYSTALS ON NATURAL CLINKER FROM THE SANTA BARBARA MINE, CAVRIGLIA

The spontaneous combustion of lig- nite and the transformation (T> 800 ° C) of the clayey host rocks into linker is an extremely widespread phenomenon in nature but little known among geologists and mineral collectors. Lo- cally, temperature may exceed 1200°C and  host  rocks  can  melt  producing small  flowing  volumes  of  lava  called “paralava”.  Natural  clinker  is  a metamorphic rock while paralava can be considered  as  a  true  magmatic  rock. Thanks  to  the  high  SiO2 and Al2O3 contents in clay, the resulting natural clinker  and  paralava  consist  usually of  an  assemblage  of  aluminiferous clinopyroxene and spinel, fayalite, se- kaninaite  (Fe-cordierite),  mullite  and sulfides.  When  the  host  clay  is  rich in  calcium,  an  even  more  complex paragenetic  assemblage  can  form  including  rare  minerals  like:  indialite, ferroindialite,  kirschteinite,  melilite, kalsilite,  fresnoite,  kinoshitalite,  srebrodolskite, esseneite, barioferrite and ellestadite. The color of natural clinker and paralavas range from orange-red to brownish-black  strongly  contrasting with the grey color of the original un- heated clay. Until 1994, Santa Barbara mine (Cavriglia, AR) exploited a large lignite deposit hosted by Pliocene clay (Argille  di  Meleto  formation).  The lignite produced was mainly used in the nearby thermal powerplant while natural clinker was utilized for paving mining  tracks.  In  1957,  exploitation switched from underground to open pit operation and large outcrops of lig- nite and natural clinker/paralava were progressively exposed on the surface. Combustion  of  lignite  was  a  spon- taneous process in this area and was described by the early naturalists since the XVI century.One of the authors (LP) was hiking in the upper part of the open pit during the spring 1973. He stopped in front of a bench made by orange-red natural clinker and could observe numerous lustrous, acicular crystals covering the rock. Prismatic and acicular crystals of gypsum up to 15 cm in length lined the  fractures  of  the  rock.  Beautiful aggregates of crystals stood out on the red-brown-black matrix made of natural clinker. The mining activity proceeded rapidly and, in a frantic race against time, Leo managed to extract few hundred specimens with magnifi- cent gypsum crystals. Since many years the mine has been abandoned and new findings of gypsum in the few remaining outcrops of red natural clinker must be considered rather unlikely.
THE OLD MINES OF GIUMEGLIO NEAR POPIGLIO (PISTOIA)




The Pb-Zn old mines of Giumeglio are one of the relics of the historic mining activity located in the Pistoia province  (Tuscany).  They  were  described by Antonio Matani in 1762, their  mineralogy  was  studied  only recently.  In  this  paper,  new  historical and mineralogical data are given. Primary ores are represented by galena,  sphalerite,  and minor  pyrite. The  sulfide  assemblage  is usually altered  into  secondary  minerals like smithsonite,  hydrozincite,  anglesite, and hemimorphite. In addition, lemon-yellow coatings  of  greenockite/ hawleyite are relatively common.
BEYOND THE BAZZITE – OTHER NEWS IN THE AMBIN MASSIF (TO)


The exploratory tunnel of “La Maddalena” (Chiomonte, Susa Valley, Italy) is the Italian shaft of Ambin base tunnel for the new international line Turin-Lyon.  The  tunnel,  diameter 6.3 m and about 7000 m long, was excavated by an open TBM and has the purpose of investigate the deep- est  part  of  the  project  (more  than 2000 m of coverage). In 2016 RMI published a first article about the discovery of bazzite in an alpine cleft at pkm 0+980. Apart from that finding, other mineralogical samples were collected  during  the  excavation  of  the tunnel. This article retraces the excavation and describes the species recognised and collected up to pkm 7+020, the end of the exploratory tunnel.
Abstrat ITALIAN MINERALOGICAL MAGAZINE
nr. 2-2021
MIMETITE FROM VALSASSINA, THE CONTRA VALLEY MINE


The Contra Valley mine, near Primaluna, Valsassina, represents the best collecting site for mimetite in Lombardy. This lead arsenate occurs in very nice specimens showing yellow or green hexagonal prismatic crystals, often forming aggregates of hundreds of small crystals, covering large areas of the specimens. They are aesthetically appealing even if not ob- served under a binocular microscope. The article deals also with several oth- er minerals, associated with mimetite, which were collected during years of research done by the authors.
HAÜYNE OR LAZIALITE?


This article explains how and why haüyne, a typical mineral of Lazio, should have been called lazialite, a name attributed by Father C.G. Gismondi to the mineral he discovered in 1803, instead of ignoring any priority and naming it haüyne by T.C. Bruun de Neergaard in honor to René Juste Haüy in 1807, all that without even Haüy´s approval. This article demonstrates how the sample existing at the Muséum na- tional d’Histoire naturelle in Paris cannot be the holotype as well, and how the type locality is also wrong,being not Monte Somma-Vesuvius (Naples, Campania), but the crater of Nemi (Rome, Lazio). A recent personal communication from M.E. Back to V. Nasti (2019-2020), con- firms that in the 2022 edition of the well-known “Fleischer’s Glossary of Mineral Species”, at least the type lo- cality will be corrected, from Monte Somma-Vesuvius to Nemi , without giving the mineral its original name back, and therefore without doing justice to Gismondi.
MERLINOITE, A NEW FIND FROM TREVIGNANO ROMANO.


This article describes a specimen of merlinoite, occurring as microscopic, radial aggregates of prismatic crystals, found in a leucitic rock from Fosso Fossaccio near Rome. This is a new locality for this rare zeolite group mineral. Merlinoite has been studied and identified  using  Scanning  Electron Microscope (SEM) and single crystal X-ray diffraction.
SMOKY QUARTZ FROM GALLURA, SARDINIA


Gallura is a subregion in north-east- ern Sardinia. Large part of the terri- tory, from a geological point of view, is characterized by granite rocks belonging  to  the  Sardinian Corsican Variscan  batholith.  This  article  de scribes the most important finds of smoky quartz specimens, reaching up to up to eighty centimeters across and weighing over 50 kg.
These  crystals  occur  in  pegmatite pockets. The research of the pockets was mainly focused on several active and abandoned quarries, located in the Gallura subregion, which include four different areas where is still possible to find quartz crystals within peg- matite pockets.
Abstract ITALIAN MINERALOGICAL MAGAZINE
nr. 3-2021
TUR2021
FIELD TRIP GUIDEBOOK
3rd International Conference on Tourmaline
TOURMALINES FROM ELBA ISLAND:
GEOLOGY AND GENESIS


Elba Island has been famous since ancient times primarily for its iron deposits, which have been known and worked for over 2000 years by the Etruscans, the Romans and many sub- sequent inhabitants. The discovery of the first multicolored tourmaline specimens, evidencing the existence of gem-bear- ing pegmatites, dates back to the late 18th Century. During the 19th Century the area of Campo nell’Elba (and in particu- lar the villages of S. Piero and S. Ilario on the eastern slope of the Mount Capanne monzogranite pluton) became one of the most important mineralogical classic localities in Italy and Europe. It was essentially due to the discovery of a large num- ber of magnificent mineral specimens, primarily polychrome tourmaline crystals and associated pegmatitic minerals. Sci- entific research, performed on specimens from both historic museum collections and new field exploration, has allowed the identification in the Elba island of a large number of species belonging to the tourmaline supergroup, which include:
- elbaite, fluor-elbaite, schorl, foitite, rossmanite, tsilaisite, fluor-tsilaisite and celleriite (all of pegmatitic origin);
- dravite, uvite, magnesio-lucchesiite (of non pegmatitic origin).
It is noteworthy that the Elba island is the type locality for elbaite, tsilaisite, fluor-tsilaisite, celleriite, magnesio-lucchesiite and uvite.
In addition to the worldwide famous tourmalines occurring in gem-bearing pegmatites, other findings are reported from other localities throughout the Elba Island, both in magmat- ic and metamorphic rocks.

GEOLOGICAL OUTLINES
The structural framework of the Elba Island is classical- ly divided into five tectonic complexes that were stacked on east-verging  thrusts  during  the  Apenninic  compressional events before 20 Ma. The three lowest complexes (Complexes I-III) have continental features, consisting of metamorphic basement  and  shallow-water  clastic  and  carbonate  rocks,while the upper complexes (Complexes IV and V) have oceanic characteristics, including ophiolitic sequences.
During the last 10 Ma, the northern end of the Tyrrhenian Sea underwent an extensional process leading to the opening of an ensialic backarc basin behind the eastward-progressive compressive front of the Northern Apennine mobile belt. In this framework, magmas were generated in the mantle and interacted with crust-derived felsic magmas to give rise to the variety of intrusive and extrusive products of the Tuscan Magmatic Province, to which the intrusive rocks of Elba Is- land belong.

LATE MIOCENE INTRUSIONS, BORON AND TOURMALINE FORMATION
The peraluminous, Late Miocene magmatism of the Elba Island provides the opportunity to observe a wide variety of granite and hydrothermal rocks containing several mem- bers  of  the  tourmaline  supergroup  minerals.  Crustal-derived granite magmas formed at the base of the crust during the post-collisional stage of the Apennine orogeny, then they were sequentially emplaced in the shallow crust between 8.5 and 5.9 Ma. Emplacement of magmas occurred exploiting structural and stratigraphic traps at both plutonic (mon- zogranites, microgranites and pegmatites; at ca. 4-6 km) and sub-volcanic crustal levels (granite porphyries; at ca. 2-4 km). Plutonic bodies triggered the formation of contact aureoles, while the thermal effects around sub-volcanic bodies were negligible. In both cases, B-rich aqueous fluids issued by the crystallizing felsic magmas produced widespread hy- drothermal effects, including the formation of metasomatic rocks and veins mainly composed by tourmalines, as well as hydraulic breccias cemented by this cyclosilicate.
In the biotite-bearing Monte Capanne monzogranite plu- ton (western Elba; 6.9 Ma) as well as in the biotite-cordierite Porto Azzurro monzogranite pluton (eastern Elba; 5.9 Ma), tourmaline is a late-magmatic accessory mineral.  Here,  schorlitic-dravitic  tourmalines  crystallize  in the latest stage forming irregular globular nodules. Tour- maline becomes a fundamental rock-forming mineral in the cordierite-bearing San Piero microgranite dykes-sills (western Elba; 6.9 Ma) and in the Calamita microgranite dykes-sills (eastern Elba; 5.9 Ma). In both cases, tourmaline forms tiny euhedral crystals with textural features suggesting a quite unusual early crystallization. In the eastern Elba, a widespread boron metasomatism of the micaschist host occurred at the contacts with the Calami- ta microgranite dykes-sills. Schorl, dravite and probably uvite (only semiquantitative data are available at present about such minerals) have been found as microgranular vein infill and breccia cement as well as metasomatic ag- gregates replacing the biotite-rich layers of the micaschist. The most famous tourmaline-bearing rocks in the Elba Is- land are represent by LCT gem-bearing pegmatites. From their pockets, the wonderful specimens have been extracted since the late 18th century and the occurrence of a significant number of species belonging to the tourmaline supergroup. The LCT gem-bearing pegmatite dykes crop out only along the eastern edge of the Monte Capanne pluton, strictly asso- ciated with the (cordierite-tourmaline)-bearing microgran- ites. They are hosted by both monzogranite and metamor- phic rocks, close to the magmatic contact. The polychrome crystals found in the cavities show an amazing crystal-chem- ical variation, even along a single crystal: schorl, tsilaisite, fluor-tsilaisite, elbaite, fluor-elbaite, rossmanite, celleriite and foitite. The astonishing diversity also recurs in the hydrothermal veins produced by the B-rich fluids that, after escaping the pegmatite bodies, interacted with the mafic and ultramafic rocks of the metamorphic aureole. Here, depend- ing on the chemical composition of the host, uvite, dravite and magnesio-lucchesiite can be found.
Moving from plutonic to sub-volcanic level, the overall ge- ochemical composition of magmatic rocks consists of B-rich peraluminous granite. However, the colder emplacement environment  and  the  lower  confining  pressures  produced major variation of the textural characters. The granite por- phyries are characterized by variable amounts of phenocrysts (quartz, feldspars, biotite; 20-45 % vol) set in a very fine- grained groundmass. Tourmaline occurs as late-magmatic globular-spheroidal orbicules/nodules, usually showing the typical fibrous-radiating internal texture. Schorlitic-drav- itic tourmalines commonly occur, but unusual compositions enriched in dutrowite and olenite components have also been found. A thorough study of these tourmalines is still lacking. The most spectacular example of orbicular tourmaline bearing porphyries in Elba is represented by the Capo Bianco Aplite. According to geological and petrological data, this rock could be a prime example of the immiscibility process in (B-Li-F)-rich, peraluminous felsic magmas.

SHORT NOTES ON THE LATE MIOCENE TECTONO-MAGMATIC EVOLUTION OF THE ELBA ISLAND (LATE MIOCENE)
The interpretive sketch of the Late Miocene tectono-magmatic evolution of Elba Island is based on studies by Dini et al. (2002), Maineri et al. (2003), Westerman et al. (2004) and Rocchi et al. (2010).
During the Early Miocene stage, the orogenic belt reached its maximum thickness acquiring the intricate architecture recorded by the stack of tectonic units in the island. Since the middle Miocene, the tectonic regime in the area changed from compressional to extensional due to the progressive east- ward roll-back of the west-dipping Adria subducting plate. This process created the intracontinental Northern Tyrrhe- nian back-arc basin characterized by a significant thinning of the continental crust (from 30-40 km to 22-25 km) and the upwelling of the asthenosphere. The net result was the onset of partial melting processes at the base of the metasedi- mentary continental crust. The partial melting of the meta- sediments was also enhanced by under and intra-plating of mafic magmas formed in the underlying mantle.
The Late Miocene magmatism recorded in the Elba Island was characterized by multiple injection of crustal peraluminous felsic magmas and only minor volumes of  mantle-derived  magmas.  Magmas  were  sequential- ly transferred from the base of the crust to very shallow crustal levels (1-6 km) producing a subvolcanic complex,two plutonic complexes and two late mafic dyke swarms. Magmatism was diachronous: a first prolonged event was responsible for the products we observe in central-western Elba (8.5-6.85 Ma); a second event occurred in Eastern Elba around 6.4-5.9 Ma.
The first intrusive event (8.5-7.44 Ma) created a multi- layer subvolcanic complex made by dykes, sills and lacco- liths that were emplaced at shallow depth (1.5-4 km) in the uppermost Ligurian Units. The subvolcanic complex records at least three distinct injection of magma: 1) the strongly peraluminous Capo Bianco Aplite (8.5 Ma); 2) the peraluminous Portoferraio granite porphyry (8 Ma); 3) the peraluminous San Martino granite porphyry (7.44 Ma). Meanwhile, the partial melting of the lower crust continued to produce new granite magma which, rising towards the surface, accumulated at the base of the Subvol- canic Complex (4-6 km), forming the large monzogranite pluton of Monte Capanne (7.4-6.9 million years) and its contact aureole. Tourmaline-bearing leucogranites and the famous LCT pegmatites formed in the final plutonic stage and they were crosscut by a swarm of mantle-derived mafic dykes (Orano porphyry; 6.85 Ma).
Accumulation of large granite intrusions in the shallow crust caused oversteepening that accelerated extensional deformation, triggering the extensional gravity sliding of the upper part (subvolcanic intrusions) of the magmatic complex. The granite porphyries, originally on the top of Monte Capanne, were displaced eastward and nowadays crop out in central Elba, while Monte Capanne pluton was progressively ex- humed to the surface in western Elba.
About half million year later, magmatism migrated to the east and, between 6.4 and 5.9 Ma, produced the plutonic complex occurring in eastern Elba made by a monzogranite pluton and a swarm of tourmaline-bearing leucogranite sills-dykes. These felsic products were later crosscut by a swarm of mantle-derived mafic dykes (Monte Castello porphyry; ca. 5,9 Ma). Also in this case, oversteepening was responsible for the rapid tectonic exhumation of the magmatic complex.
TUR2021
FIELD TRIP GUIDEBOOK
THE EASTERN ELBA MAGMATIC-HYDROTHERMAL SYSTEM AND ASSOCIATED ORE DEPOSITS

This one-day field trip has the goal to illustrate some tour- maline occurrences related to the eastern section of the Elba Island. In this area, the low-angle Zuccale fault separates a lower plate, characterized by Late Miocene granite intru- sions, contact metamorphism and circulation of high-tem- perature  boronrich  hydrothermal  fluids,  from  an  upper plate characterized by a widespread formation of iron de- posits (hematite-pyrite and pyrite-pyrrhotite in association with hedenbergite-ilvaite skarn).
Beside of a series of acidic, tourmaline-bearing intrusives, in the coastal area of Barbarossa - Terranera, it will be possible to visit the small ore deposit of Terranera and the larger ore deposits of the Rio Marina area. The visit to Rio Marina will include a tour to both the abandoned mines and the Mining Museum, organized by the Parco Miner- ario dell’Isola d’Elba, which was founded after the closure of the ore mines in the late 1980s and, at present, it belongs to the Municipality of Rio, which includes the villages of Rio nell’Elba and Rio Marina. On the occasion of the conference, the Florence University Museums System will organ- ize at the Mining Museum the exhibition “Masterpieces of Elba’s nature”, in which a group of extraordinary historic mineral  specimens  with  magnificent  tourmaline  crystals from San Piero in Campo will be on display The group will be collected after breakfast in Portoferraio at 8:20 a.m. (lunch boxes collected in the Hotel reception).
Transfer to Porto Azzurro area (ca. 25 minutes) and arrival at Barbarossa Beach at 9:00 a.m.. Here we will start walking  along  the  coast  looking  at  tourmaline-bearing monzogranites, microgranites and nice boron metasomat- ic effects on the micaschist host. The walk is a represent- ative upward transect from the lower plate (micaschist + granites) where magmas stopped producing very high tem- perature hydrothermal systems (tourmaline-rich), across a low-angle extensional faults (Zuccale Fault), to the upper plate (made of a stack of sedimentary and metamorphic units) where medium-to-high temperature hydrothermal fluids produced the well-known iron ore deposits (Terrane- ra, Rio Marina, Rio Albano).
The group will reach Reale Beach and Terranera mine (hematite-pyrite) and, after the discussions, it will be collected by the bus for the transfer to Rio Marina for the lunch. Here we will visit the classic localities of Torre di Rio (ilvaite-hedenbergite skarn) and the Rio Marina mine (hematite-pyrite ores).

9:00-10:00 a.m.: from Barbarossa Beach to Reale Beach Sills and dykes of tourmaline bearing monzogranite and microgranite. Widespread replacement of the biotite-rich layers of micaschist by tourmaline. Walking along a small road to the Reale Beach (20 minutes).

10:00-11:30 a.m.: Terranera Beach and mine
The visit will be continued from the Reale Beach towards Terranera, walking along a path that will allow the exami- nation of a series of magmatic rocks intruded in micaschist and, approaching the top of the lower plate, the increasing effects of the hydrothermal alteration (quartz-“adularia” veinlets) until we will reach the Zuccale low-angle fault. The Zuccale Fault represents a major tectonic discontinuity that acted as a sink for hydrothermal fluids, focusing alteration/ mineralization effects. Here we will see a change in the alteration type. Chloritization becomes predominant and hematite-pyrite disseminations and veinlets increase. Crossing the sub-horizontal fault, we will pass into the upper plate (here made by Permian black shales and Triassic quartzites) and we will reach the Terranera mine. Large bodies of microcrys- talline hematite were exploited in the past and the resulting open pit is now replaced by a “nice” green lake separat-ed from the sea by a sandy beach mostly made of hematite shining grains. We will be able to spend some time looking at hematite stockworks and massive bodies of hematite whose cavities contain some of the best pentagonododecahedral pyrite crystals ever found in Elba.
At 11.15 a.m., way back to Reale Beach (11:30 a.m.) for the bus transfer to Rio Marina (arrival on 12.00 a.m.).
The bus will move the group to Rio Marina (ca. 30 minutes) for the visit to the Torre di Rio skarn (ilvaite-heden- bergite-epidote) and, later in the afternoon, both the Mining Museum and the Rio Marina mine (hematite-pyrite). Although tourmaline is very rare in the latter ore deposits, recent geochemical investigations indicate that the iron ores are characterized by anomalous concentrations of Sn, W, B and Li, providing evidences for their relationships with the peraluminous magmatism. The bus will leave the group at the Rio Marina harbor.
12:00 a.m. -1:00 p.m.: Torre di Rio skarn
This is one of the best exposures of ilvaite-hedenbergite skarn in Tuscany. This is the type locality for ilvaite. Thanks to the new detailed mapping of this skarn body, the group will learn the relationships between the type of replaced rocks (pure marble, calcschists, schists), degree of fracturing, interference between low and high-angle faults and the distribution of pockets. Superb crystals of ilvaite (up to 10 cm), hedenbergite, arsenopyrite, quartz and calcite frequently line the skarn pockets. A small pyrrhotite-arsenopyrite body was discovered at the core of the skarn body.
After the visit we will walk back (15 minutes) to Rio Ma- rina village to have lunch and then visit the Mining Park Museum and the iron mine.
1.00-2.00 p.m.: lunch in Rio Marina 2:00-3:00 p.m.: Mining Park Museum
Visit to the mineralogical museum. In the “Museo dei minerali e dell’arte mineraria” of the “Parco Minerario dell’Isola d’Elba”, along with the permanent exhibition that displays a nice collection of mineral specimens typical of the Rio Marina area (hematite, pyrite, ilvaite, quartz varieties, etc.) and of pegmatitic specimens from Mount. Capanne, the special exhibit “Masterpieces of Elba’s nature”, curated by Vanni Moggi Cecchi and Lucilla Fabrizi, will be presented. The exhibition, opened from June to November 2021 and on display for TUR 2021, will show a selection of historic pegmatitic specimens containing aggregates of magnificent crystals of polychrome tourmaline, beryl, quartz, spessartine and pollucite, belonging to the Mineralogical collection of the “La Specola” Museum – Florence University Museums System
3.00-5.00 p.m.: Mining Park and ore deposits of the Rio Mine
We will enter the Rio Marina mine by minibus reaching the last mining stope that was exploited in 1980: Valle Giove. Valle Giove is an open pit where, along the  benches,  small  hematite-pyrite  bod- ies are still exposed. Orebodies are made of micaceous fine-grained hematite and microgranular pyrite accompanied by “adularia”  and  quartz.  Ore  fluids  re- placed  the  quartzite-metaconglomerate layers of the Triassic Verrucano formation (quartzite-phyllite-metaconglomerate  sequence), while the phyllite layers were less pervasively altered to a chlorite-rich assemblage. Locally, the massive tabular bodies of fine-grained hematite-pyrite were fractured during the hydrothermal event leading to the for- mation of large open fissures, lined by a layer of coarse-grained micaceous hematite with nice pentagonododecahedral crystals of pyrite (from few mm up to 10 cm).
The largest ore body occupied the NW upper part of the open pit. Here, the opening of a dilational jog produced a large volume of brecciated phyllites and quartzites that focused the ore fluids.
The hydrothermal reaction was extreme and the phyllites also were almost totally converted to an assemblage of “chlorite”, epidote, “adularia” and quartz. Both the chloritized rock and the fine-grained hematite-pyrite ore experienced a pervasive veining of coarse-grained micaceous hematite that, thanks to the availability of several large voids in the brecciated body, developed an unusual concentration of large cavities with wonderful pentagonododecahedral crystals of pyrite (up to 15 cm). During the past 20 years, the Rio Marina Mining Park did some exploratory excavations in a residue of this body and many beautiful specimens were collected.
Time permitting, the participants will be accompanied through the old stopes, from Valle Giove to the southernmost Bacino stope, one of the best areas of the mine for collecting the famous clusters of hematite crystals with highly complex rombohedral habitus.
5:00 p.m.: return
The group will be collected by the minibus at the Bacino stope to return to Portoferraio, where the arrival is scheduled for 5:40 p.m..
End of the excursion
TOURMALINES FROM SAN PIERO IN CAMPO AND OTHER MINOR OCCURRENCES FROM THE ELBA ISLAND



DAY 1 (SUNDAY, SEPTEMBER 12TH, 2021)
Theme: Tourmalines from the famous San Piero- Sant’Ilario LCT gem-pegmatite dykes and their plutonic and metamorphic host rocks
This day the field trip will bring participants through a well exposed LCT gem-pegmatite dyke swarm that developed at the contact between the slightly peraluminous Monte Capanne monzogranite pluton and its contact aureole. It is one of the youngest LCT gem-pegmatite complex in the planet (6.9 Ma). Thanks to the very young age, the petrologic study of the- se rocks avoided the usual problems encountered in old systems (difficulties in the application of radiogenic isotope systematics due to error propagation with age; tectonic-metamorphic-hydrothermal reworking, etc.). For these reasons, the petrologic comparison of pegmatites with the potential monzogranite and leucogranite parents was possible providing us impor- tant insights on the behavior of these systems. Additionally, the overall small size of these pegmatite dykes allows for the study of structure, texture, mineralogy and geochemistry at a more manageable scale than in most large LCT pegmatites. The large number of pegmatitic dikes showing different de- grees of geochemical evolution and the various types of host rocks allowed the development of variable compositions in tourmaline crystals, resulting in the occurrence of a quite large number of species.

8:20 a.m.: start
The group will be collected at 8:20 a.m. after breakfast in Portoferraio (lunch boxes collected in the Hotel reception). Transfer to San Piero in Campo and arrival at the Bontem- pelli quarry at 9:00 a.m.

9:00-9:40 a.m.: Bontempelli quarry
Most of the productive San Piero-Sant’Ilario LCT gem-peg- matite dykes are hosted by the intrusion at the very contact with the metamorphic aureole and due to the small-scale excavations (few m down dip) our knowledge of the deeper feeding system is very limited. Fortunately, the exploitation of the Monte Capanne granite for dimension stone produced larger and deeper quarries, mostly located at the southern edge of the LCT pegmatite dyke swarm. Bontempelli quarry is placed just 200 m SW of the Rosina pegmatite dyke, and about 600 m from the famous locality of Fonte del Prete. It is a quite deep quarry exposing one of the best vertical sections of the roof of the pluton and allowing us to observe the lower- most feeding part of some minor pegmatite dykes.
This quarry exploited granite of the so-called San Piero facies. This monzogranitic facies lack the K-feldspar me- gacrysts that characterize the other important intrusive facies of the Monte Capanne pluton: the Sant’Andrea facies. Most of the quarry is in the San Piero facies but K-feldspar megacrysts appear moving to the east and, as we approach the contact with the metamorphic aureole, their number progressively increases (Sant’Andrea facies). The contact with the host metamorphic rocks passes a few meters above the upper margin of the quarry.
Here, a small LCT pegmatite dyke (some pink elbaite cry- stals have been found as floaters in the soil of the gardens above!) has been cut by the quarry. In the upper part of the bench (2-3 m), the 20 cm thick pegmatite dyke has the typi- cal tabular structure and texture (mostly aplitic with local axial pegmatitic portions) with sharp contacts against the granite host. Going down, the dyke becomes more sinuous and irregular assuming, at the base of the bench (ca 10-15 m below the margin of the quarry) an anastomosing pattern with gradational contacts against the monzogranite host. This evidence provides important information about the rheology of the monzogranite host and the flow mechanism of the pegmatitic melt. The sharpness of the pegmatite dyke in uppermost part, closed to the contact, indicates that the external shell of the intrusion behaved more rigidly than the inner part where the pegmatite melt emplaced through a sinuous “fracture” network. The gradational contacts between pegmatite and monzogranite in the lower part may indicate that the monzogranite was not totally crystallized and that magma mingling was allowed at the interface. The different behavior could be tentatively explained by two distinct processes: i) temperature-controlled – The roof of the pluton granite was subjected to a strong thermal gradient. The external shell was already totally crystallized (subsolidus) and tectonic dilation produced sharp fractures, while in the internal part, still containing a melt fraction, deformation developed as a braided vein network; ii) strain-controlled – The pluton was still in a suprasolidus condition and a melt fraction was present through the whole observed section. The different fracture pattern was controlled mostly by the higher strain rate acting at the very contact of the pluton.
As far as time is concerned, the first hypothesis would be relati- vely late compared to the second because the pluton would have already lost a considerable amount of heat to the host rocks. In the western, deeper, part of the quarry the San Piero mon- zogranite facies contain several spots made by black tourma- line and quartz. The monzogranite is also cut by thin veins of tourmaline.
A) The Prado quarry with the pegmatite dykes and the contact between pluton and metamorphic aureole highlighted; B) Detail of the western dyke showing the typical textures; C) Polychrome elbaite crystal associated with orthoclase, quartz and lepidolite from a cavity of the San Piero in Campo pegmatites (Natural History Museum, University of Pisa).
Photos e grafica A. Dini.

9:40-10:00 a.m.: transfer
The group will be collected by bus (near the Bontempelli quarry) and moved to the starting point (at 9:50 a.m.) of the descending path to the Grotta d’Oggi quarry. The group will leave the bus with the backpacks (water, some food, etc.) and will go for a walk of about three hours in the Grotta d’Og- gi area. Here many pegmatite dykes crop out. Some were exploited in the past and provided the wonderful specimens exposed in many mineralogical museums all over the world. Other dykes have been found (and/or re-discovered) more recently providing amazing tourmaline specimens. The de- scent to Grotta d’Oggi is about 1 km with change in altitude of ca. 120 m. It takes about 20 minutes walking slowly.

10:00-12:45 a.m.: Grotta d’Oggi quarry
Attitude, textures and mineralogy of the most famous productive LCT pegmatite dyke system in Elba Island (type locality for tsilaisite and fluor-tsilaisite). Searching for crystals in the old dumps. Discussion will focus on mineralogy, textures and geometry of pegmatite dykes, introducing topics that will be deeply discussed in the afternoon stops. There is the opportu- nity to visit nearby minor dykes (Fucili, Cechi, Liborio, Grotta d’Oggi north-Graziano) and the old magnesite quarry (on the way back to the bus) where a nice stockwork of magnesite-dolomite-quartz veins is hosted in carbonated serpentinites. The ascent back to the bus will be more demanding than the descent and will take ca. 30 minutes, walking uphill to reach the bus on the main road (12:45 a.m.). Transfer by bus to San Piero in Campo (ca. 10 minutes).

2:00-2:30 p.m.: Facciatoia
After the lunch, the group will visit the Facciatoia classic locality. Here we will do observation at the contact betwe- en the pluton roof and the contact aureole (metabasalts and metaserpentinites) where pegmatite dykes are hosted by both metaophiolites and monzogranite. Metabasalts close to the pluton contact host small hydrothermal veins of uvite, some- times with nice crystals in cavities.
Attitude,  textures  and  mineralogy  of  productive  LCT pegmatite dykes (famous for beautiful “rubellite”); rela- tionships between pegmatites, monzogranites and contact aureole.

2.30-3.00 p.m.: walk
From Facciatoia the group will move along an itinerary of about one kilometer, from San Piero in Campo to the Rosina pegmatite dyke, starting from a panoramic view of the famous historic pegmatitic localities of Fonte del Prete/ Filone della Speranza, Masso Foresi, and Il Prado.. The path for the Rosina dyke will also pass through Pietra Pin- zuta with abandoned magnesite quarries with tourmali- ne-rich leucogranitic veins.

3:00-3:30 p.m.: San Rocco
From the San Piero cemetery, down along the old path for the Prado quarry. Visit to an outcrop of metaserpentinite rocks with hydrothermal veins where the best specimens of magnesio-lucchesiite were collected.

3:30-4:30 p.m.: Prado dykes
Attitude, textures and mineralogy of a productive LCT peg- matite dyke; relationships between pegmatites, microgranites, monzogranites and rocks of the contact aureole. Beautiful expo- sures of line rock at the footwall of a pegmatite dyke. Walking down 5 minutes along a small path to the Rosina dyke.
4:30-6:00 p.m.: Rosina dyke
Attitude, textures and mineralogy of a productive LCT pegmatite dyke; relationships between pegmatites, micro- granites and monzogranites. Tourmalines distribution and zoning (type locality for celleriite). This is one of the best exposures of pegmatite in the area. Walking down 10 minutes to the main road below the Bontempelli Quarry.

6:20 p.m.: return
The group will be collected at 6:20 p.m. on the road near the Bontempelli Quarry. Arrival in Portoferraio about 7:00 p.m.

DAY 2 (MONDAY, SEPTEMBER 13TH, 2021)
Theme: Tourmaline from plutonic to subvolcanic settings Today we will have an interesting view of tourmaline from both plutonic and subvolcanic settings. In subvolcanic gra- nite porphyries (emplaced at 1-3 km depth) tourmaline crystallizes as a late magmatic (spots and orbicules) and hydrothermal (veins, breccias) phase like in the plutonic rocks. The main difference is the total lack of pegmatites in subvol- canic rocks. Another trait d’union with the plutonic setting is the rare occurrence of small miarolitic cavities (mm to few cm) like those seldom observed in some other granophyric in- trusions in the world (e.g., Torres del Paine, Patagonia, Chi- le and Cuasso al Monte, Lombardy, Italy). It is well known that tourmaline does not crystallize in volcanic rocks (the few occurrence of tourmaline in rhyolites, like in Macusani, SE Perù, and San Vincenzo, Tuscany, Italy, are xenocrysts) and it would be really useful to develop a discussion about physical-chemical factors that limit tourmaline formation at very shallow crustal depth.
8:20 a.m.: start
The group will be collected at 8:20 a.m. after breakfast in Portoferraio (lunch boxes collected in the Hotel reception). Transfer to the south-eastern side of the Island passing throu- gh Capoliveri village and the Calamita mine (magnetite and  hematite  in  hedenbergite-ilvaite-garnet  skarn).  We will park the minibus in a mining yard of the Ginevro mine (magnetite in amphibole-pyroxene-garnet skarn). The mine exploited some sub-vertical bodies hosted in micaschists. The touristic visit to the open pit and tunnels is managed by the Caput Liberum Cooperative (Capoliveri), but unfortuna- tely, we will not have enough time to add it to our trip.
9:20-11:20 a.m.: The Punta Bianca beach
Along the downhill path from the parking to the beach we will see several blocks of amphibole-magnetite skarn thrown into the dump from the nearby Ginevro mine. The cliffs along the beach expose the micaschists cut by tourmaline-bearing leucogranite, amphibole skarn veins and veins/brec- cias with several generations of tourmaline infill. The main outcrop at Punta Bianca beach is one of the most spectacular in the island to appreciate the emplacement style of the tour- maline leucogranite. The nearby Punta Bianca provide a wonderful exposure of these dykes where we can walk and observe structural and textural variations inside the dykes and the relationships with the micaschist and faults.

11:20 a.m.-1:30 p.m.: Monumento road
The group will move back to the parking for the next transfer by minibus to Marina di Campo (ca. 40 minutes). Along the Monumento road, between Lacona and Marina di Campo, short stop to visit an outcrop of subvolcanic monzogranite porphyry (San Martino Porphry) with tourmaline in spots and euhedral crystals in miarolitic cavities. The road cuts display a nice outcrop of the monzogranite porphyry rich in K-feldspar megacrysts (HT sanidine). This outcrop is part of the largest subvolcanic laccolith of the island emplaced ca 7.4 Ma into the Cretaceous flysch. The estimated depth of emplacement was 2-3 km. The rock is partially altered (chloritization of biotite phenocrysts) but the texture and the mi- neralogy is still well preserved. The rock contains many spots of tourmaline and, locally, a variable number of miarolitic cavities, ranging in size from a few mm to some centimeters. In larger pockets, tourmaline occurs as black prismatic crystals, sometimes with a brush-like termination; these crystals are chemically zoned, with variable Fe/(Fe+Mg) content. However, available data allow their classification as schorl. In the smaller miaroles, tourmaline occurs with different habits and colors. Indeed, habit can range from prismatic to acicular, and color can vary from colorless to blackish, pas- sing through green to bluish individuals. Studied tourmali- ne crystals have schorl-dravite composition, even if some in- dividuals show foitite composition. In the miarolitic cavities, tourmaline is associated with “adularia”, anatase, beryl, chamosite, green fluorite, and muscovite. Tourmaline in the spots is schorl-dravite in composition but, when spots are in contact with early biotite phenocrysts, a selective reaction oc- cur producing a Ti-enrichment, potentially approaching the dutrowite end member composition.
After this short stop, we will pass through Marina di Campo (1:15 p.m.) and we will reach the Paolina Beach at 1:30 p.m. for the lunch.

1:30-2:15 p.m.: lunch time
The Paolina Beach lunch site is perfect for swimming and to eat a sandwich sitting on top of line rock pegmatite boulders!

2:15-2:45 p.m.: Paolina Beach
This stop will bring us back to the yesterday topic. This is the northernmost LCT pegmatite dyke of the San Piero-Sant’I- lario dyke swarm. We will stop here for logistic reasons and to have a short look at very interesting, layered pegmatite textures (line rocks) before continuing our trip on subvolcanic tourmalines. The observation must be conducted on boulders because the pegmatite dyke is buried in the beach. There are textural (line rock) and mineralogical (altered petalite crystal) evidences that this dyke is quite evolved. Tourmali- ne locally occurs as multicolored crystals “frozen” in quartz and albite aggregates locally replacing probable previous pe- talite crystals.

2:45-3:15 p.m.: transfer to the Sansone Beach
The minibus will remain on the main road, and we will walk downhill for 10 minutes through the Sorgente beach to the Sansone Beach.

3:30-6:30 p.m.: Sansone Beach
The white cliffs behind the Sansone Beach are made of a wonderful tourmaline bearing, layered leucogranitic por- phyry: the Capo Bianco Aplite. It is a portion of a large sill that was emplaced at very shallow level in the crust (host rock is non-metamorphic Cretaceous flysch) and is part of the laccolith-sill-dyke subvolcanic complex of central Elba. The group will discuss about the meaning of tourmaline orbicules, magmatic layering, porphyritic texture and so on. This rock is considered as an exceptional example of a pegmati- te-like magma that escaped the plutonic level, experiencing tremendous immiscibility processes.
The Sansone Beach is a very beautiful place, ideal for geologic observation but also for enjoying the sun while admiring the view, swimming or having a drink in the nice pub per- ched on the cliff. We suggest the participant to bring swim- ming suite, towel and, depending on habits, elegant dressing for the late afternoon “exclusive” aperitif on the cliff!

6:30 p.m.: return
The group will have to go back to the minibus. At 7:00 p.m., transfer by bus to the hotel in Portoferraio (10 minutes from the parking). Arrival in Portoferraio about 7:10 p.m..
End of the excursion
QUARTZ CRYSTALS
FROM
THE BIODOLA-PROCCHIO AREA (ELBA ISLAND)
first part


The outstanding mineral specimens from the Rio Marina iron mines and from the Monte Capanne pegmatites have been actively sought by mineral collectors since a long time. However, there are many other minor localities in the Elba Island able to give the possibility of finds of a certain importance and which are well represented in many historical mineralogical collections (rodingites and calcsilicate veins in the metamorphic aureole of the Monte Capanne pluton; quartz veins in sedimentary rocks and granite porphyry of central Elba; miaro- litic cavities in the granite porphyry of central Elba). Among these minor localities, the area between Biodola and Procchio stands out for having provided  relevant  colorless  quartz  crystals since the end of the 1700s. These crystals are characterized by the presence  of  large  fluid  inclusions,  complex habitus (hoppers, scepters) and rarely rounded complex termination. The  quartz  crystals  are  hosted  by small veins and fissures that cut the granite porphyry (San Martino porphyry) and sedimentary rocks (Flysch ad elmintoidi Fm.). Although these crystals have been known since the late  1700s,  systematic  excavations were  conducted  only  during  the 19th  century  by  the  famous  mineral collectors Luigi Celleri, Raffaello Foresi and Giorgio Roster. In 1840, these quartz veins were also visited by the German mineral dealer August Adam Krantz. After a long period of neglect, the veins were rediscovered after  World  War  II.  Currently,  the area is included within the Tuscan Archipelago National Park and mineral collecting is forbidden
QUARTZ CRYSTALS
FROM
THE BIODOLA-PROCCHIO AREA (ELBA ISLAND)
second part

The author describes its findings of quartz crystals from the Biodola-Procchio area. Quartz crystals, up to 10 cm in length (exceptionally up to 20 cm), have been collected during the 1990s. They are usually colorless or milky-white; rarely, amethystine and smoky individuals were observed. Their fascination is clearly related to their peculiar morphological features, such as hoppers and scepters, with clay inclusions, and to the abundance of fluid inclusions. Crystals are prismatic, with pseudo-hexagonal or trigonal outlines, whereas tabular individuals are rare. Different generations of quartz growth have been recognized. For instance, quartz crystals may have been fractured and then recrystallized, assuming unusual and nice morphologies. In some cases, quartz crystals seem to crystallize starting from a magmatic bipyramidal crystal of quartz belong- ing to the porphyry where the veins are hosted. A late stage generaration of microcrystalline quartz encrusts other phases (e.g., calcite).
ANATASE
FROM POGGIO CAPANNONE, PORTOFERRAIO (LI)




This  note  describes  the  discovery  of  small crystals  of  anatase  in  the  quartz  veins  oc- curring in the San Martino Porphyry, Elba Island. The author of this note found the mineral a few years ago in an old excavation, known  locally  as  “the  Professor’s trench”, just upstream of the Biodola beach, in the municipality of Portoferraio.
The so-called trench was the result of the excavation  carried  out  by  Arturo  Gianoncelli (called  “the  professor”)  in  the  early  1970s, of a quartz vein emerging due to erosion, in which there was a large cavity filled with gray clay. From here, according to what was told to the author by trustworthy people, quartz crystals up to 20 cm in length were extracted, isolated  from  the  matrix  and  recrystallized, often  rich  in  fluid  and  gaseous  inclusions. In the 1990s it was still possible to find, in the dump  of  the  excavation,  beautiful  isolated crystals of quartz up to 6/7 cm in length. The author, recently re-examining the material recovered during the various field researches under a microscope, found a few dozen samples with bipyramidal crystals of anatase, less than 1 mm in size, grown on quartz crystals or included within them. The crystals have a dark blue color when crystallized in the cavities and light  blue  when  visible  for  transparency  included in the quartz crystals
MAGNESIO-LUCCHESIITE CRYSTALS FROM SAN PIERO IN CAMPO (ELBA ISLAND)


The occurrence of tourmaline super- group minerals in the Elba Island is known since the beginning of the 19th century. In addition to the classic oc- currence represented by vugs of peg- matitic dykes outcropping in the area between San Piero and Sant’Ilario in Campo, other minor occurrences were reported by previous mineralo- gists. However, no crystal-chemical data were given, and an accurate classification of these tourmalines is lacking. In the framework of a mineralogical investigation of non pegmatitic tourmalines from Tuscany, a specimen collected by one of us (P.O.) about 40 years ago near San Piero in Campo, close to the San Rocco chap- el, was studied. Tourmaline occurs as shiny short prismatic crystals, up to 3 mm in length, black in color, associated with chlorite and mica, in fractures of a spinel + chlorite rock in the contact aureole of the Monte Capanne intrusion. This tourmaline supergroup mineral was identified as magnesio-lucchesiite, a phase recently described from Canada. The better quality of the sample from Elba Is- land allowed a full crystal-chemical characterization of this species. The specimen from San Piero in Campo is chemically unusual, being char- acterized by a very high Al content, with 7,74 Al atoms per formula unit (apfu), with 0,95 Al apfu replacing Si. Its ordered empirical formula is (formula)
The examination of the mineralogical collection of the Natural Histo- ry Museum of the Pisa University allowed to find a further specimen having the same morphology, mineral assemblage, and occurrence of the studied one. Moreover, additional specimens are kept in the Roster col- lection hosted at the Natural History Museum of the Florence University, as reported in the catalogues of the Roster collection.
A new sampling performed in June 2019 in the San Rocco chapel area allowed the collection of new specimens, in fractures of an amphi- bolrich metabasite. Crystals up to 1 cm, shiny, with a short prismatic habit, black in color, associated with titanite, pyrite, and amphibole, were found. The association with titanite and amphibole reminds to some descriptions given by mineralogists of the 19th century.
The ordered empirical formula of one crystal from this new finding is (formula)
It shows some differences with the original material, showing a lower Al content (5,57 apfu), a slightly more oxidized nature, and minor Ti. This material suggests the possible existence of a continuous series with uvite, another tourmaline super-group mineral recently described from the nearby locality of Facciatoia. The genesis of these peculiar tourmalines is likely related to the interaction between B-rich fluids, released from pegmatitic dykes, and metabasite occurring in the thermal aureole.
GARNET FROM CAMPO AI PERI (ELBA ISLAND):
A NEW FINDING


Silicate garnets are known from different geological settings in Tuscany. However,  good  specimens  are  un common and have been found only in pegmatites (e.g., spessartine from San  Piero  in  Campo)  and,  rarely, from skarn bodies in the Macei stope, Capo Calamita mine. Both occurrences are typical of Elba Island, where si- licate garnets have been known since the end of the 18th century. In addi- tion to these classic occurrences, gar- nets are known in the contact aureole developed around magmatic bodies, affecting both sedimentary and ophiolitic rocks. A new finding of nice specimens of garnet, performed in 2003 and 2004, is reported from Campo ai Peri, on the eastern slope of Monte Orello, in Central Elba. Garnet occurs as orange-red rhombododecahedra, up to 2 mm across, associated with green  prismatic  crystals  of  epidote and  milky-white  quartz,  in  quartz veins hosted in metabasalts belonging to the Complex IV of Trevisan. The chemical formula of the studied sample, based on EDS chemical analysis,
is (Ca2,73Fe2+0,23)Σ2,96(Al1,01Fe3+0,96)Σ1,97
Si3,04O12;  this  chemistry  agrees  with the  results  of  crystal  structure  refi- nement  performed  using  single-cry- stal X-ray diffraction data. Unit-cell parameter is a =  11,9454(14)  Å, V  =  1704,5(6)  Å3. This garnet can thus be classified as an intermediate member  of  the  grossular-andradite series. Antonio D’Achiardi, in his Mineralogia della Toscana, described similar specimens from San Piero in Campo; actually, this provenance is very likely wrong and may be due to an erroneous interpretation of the old hand-written labels reporting “Campo (Elba)” as the locality where those specimens were collected.
Indeed, chemical composition of this historical specimen is similar to that shown by garnet from the recent fin- dings. In the mineralogical collection of the Florence University there are some additional specimens, original- ly  belonging  to  the  Foresi  and  Roster collections, from Campo ai Peri. Other mineral collectors reported the occurrence of garnets from the area of Monte Orello.
OCTAHEDRAL GARNET FROM AFFACCATA (ELBA ISLAND)


Octahedral  garnet  was  first  report- ed from the Elba Island at the end of the 1850s, when Captain Pisani collected some samples in the area of San Piero in Campo. One year later, Bombicci published the first descrip- tion about this unusual occurrence. Later, other authors studied and described these specimens, describing  their  occurrence,  morphology, optical properties, and chemistry. In 1896, G. D’Achiardi studied octahedral garnet from a new occurrence in the locality known as Affaccata, along the path connecting La Pila with the small hamlet of Sant’Ilario in Campo. Some of the studied specimens were previously found by the mineral collector Luigi Celleri and bought by the mineralogy museum of the Pisa University. Garnet occurs associated with epidote, clinochlore, and possibly opal, in fractures of metarodingites hosted within metaserpentinite. Color ranges from color less,  to  pinkish,  to  honey-yellow and greenish-yellow. In addition to the octahedron {111}, other forms were observed, i.e., {110}, {211}, and {210}. Crystals are characterized by a very weak bireflectance. According to the mineralogists of the 19th century, chemical data suggested the classification of this garnet as grossular. Modern chemical and spectroscopic data  confirmed  such  an  identification,  showing  a  strongly  chemical inhomogeneity  mainly  related  to different Al-to-Fe3+ atomic contents. However,  since  Al  is  always  more abundant than Fe3+, the mineral is correctly  labeled  as  grossular.  The chemical  zoning  likely  records  the long  geological  evolution  of  these crystals and their host rocks.
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