Abstract ITALIAN MINERALOGICAL MAGAZINE
MINERALS, ENVIRONMENTS, ITINERARIES
Notes for mineralogical research on Mont Blanc
THE FRENCH VERSANT
Location in the western sector
Abstrat ITALIAN MINERALOGICAL MAGAZINE
Since ancient times, the hematoid quartz variety called “Jacinto de Compostela” is one of the most renowned minerals in the Spanish mineralogical tradition. This variety of quartz was called “Jacinto de Compostela” by the pilgrims traveling to Santiago de Compostela: they called it “jacinto”, that is hyacinth, because of the resemblance to the flower’s color. These quartz crystals formed within the evaporitic rocks characterizing the lithostratigraphic unit of the Keuper, Triassic in age (210-200 million years ago). The Compostela quartz can be defined authigenic because is hosted within the evaporitic rocks where it was formed.
The “Jacinto de Compostela” quartz forms complete biterminated individuals, very rarely exceeding 4 cm in length, but showing a great variety of colors (red, brown, orange, yellow, milky) and shapes (single crystals, druses, groups and clusters with different levels of compenetration). The peculiar tonality of this crystals is mainly due to hematite inclusions. The erosion caused by the rains ensures a continous renewal of the material exposed from the Keuper formation, being composed by gypsum, clay, and other soft sedimentary rocks. For such reason, nice findings of “Jacinto de Compostela” quartz are always possible in most of the mentioned localities.
Stintino peninsula is located in the northwest of Sardinia. It is characterized by the Palaeozoic units of the Variscan metamorphic basement crosscut by quartz veins.
At Cala Coscia di Donna, anatase crystals up to 1 mm, brown-reddish and rarely green were found within quartz veins. Furthermore, in the area located between Cala Coscia di Donna and Torre del Falcone, other minerals occur and include: albite, almandine, “chlorite”, ilmenite, muscovite, “ironoxides and hydroxides”, pyrite, quartz and “tourmaline”.
FROM ALPE ROSSO:
WRONG IDENTIFICATION OF
During a characterization work of beryllium minerals occurring at various locations in the Alps, few samples of Alpe Rosso "melinophane” were analyzed and they turned out to hydroxylgugiaite, a decidedly rarer mineral, approved only in 2017 as a new species on samples from Norway and Greenland.
The identification of hydroxylgugiaite took place through Raman spectrometry,X-ray diffraction from single crystal and EDS mode analysis, not excluding that gugiaite may also occur at Alpe Rosso.
RICH FROM THE MINING
SITE Of MONDAGIÒ
(VALLE DI CEMBRA, GIOVO, TN)
We report here the description of a variety of uranium-rich hydrocerussite, found on the roof of the porphyrites of the Atesino Volcanic Group (Lower Permian) at the ancient silver-bearing occurrence of the Mondagiò mining area (Giovo, Valle di Cembra, Trento). The EDS analyses showed the presence of significant quantities of uranium and the structural refinement shows a partial replacement of the Pb2+ ion by the uranyl ion UO22+ which is reflected in an increase in the unit-cell c parameter.
FROM THE CAVALLIZZA MINE,
CUASSO AL MONTE (VA)
Since 2010 several studies were carried on at the Cavallizza mine, the type locality for chukhrovite-(Ca), in order to evaluate the presence of other halides.
The studies have led to the identification of prosopite, an uncommon calcium and aluminium oxyfluoride, occurring as white aggregates, up to 1 mm across, composed by tabular crystals.
COPPER CAVE - MINE
Native copper, sometimes in association with cuprite, from the site called “Grotta Rame” in the Vallone stope, in the Capo Calamita mine, represents one of the most desirable classics of Elban mineralogy. Although the copper samples from this locality are generally of modest or relatively modest size (rarely reaching 10 cm in diameter), these stand out for the exceptional quality of the crystallizations in terms of definition of crystalline forms, luster and, sometimes, by color (almostred due to the presence of a veil of cuprite). However, information about this locality in the Elban literature is scarce and fragmentary. This article summarizes a series of information collected by the authors and also the testimonies on the locality by Renzo Casagrande, a Tuscan collector who, together with his family, frequented this area assiduously in the 1970s. Today the site is covered with mine dumps and is no longer accessible to collectors.
Abstract ITALIAN MINERALOGICAL MAGAZINE
An old specimen of sulfur from the Monti Livornesi area is kept in the mineralogical collections of the Museo di Storia Naturale of the Università di Pisa and shows the presence of bi-pyramidal crystals, up to 3 cm in size, grown on calcite. This unusual specimen promoted the study described in this paper. Indeed, the occurrence of sulfur has been known from Leghorn since the mid-19th century, where it was described by some authors from the Monte Tignoso quarries, near Ardenza, in the southern part of Leg horn. Since then, no modern findings were reported until 2011, when one of us (F.S.) discovered sulfur crystals in the eastern sector of the Monti Livornesi, close to the hamlet of Parrana San Martino. The original finding was performed in a rock sample found along the Botro Caldo, a small river located to the north of the small village of Pietre to. Unfortunately, the actual outcrop of this rock was not found. Recently, new mineralogical and geological surveys in this sector of the Monti Livornesi allowed to find further specimens in the Podere Sant’Anna and Cordecimo areas. In all these localities, a peculiar kind of rock, formed by carbonated gypsum, occur. Gypsum, sometimes in the typical swallowtail twins, is completely replaced by calcite, forming a travertine-like rock; in some vugs, well-developed sulfur crystals, up to 1 cm in size, have been observed. Crystal habit is usually bipyramidal, even if tabular or prismatic crystals have been collected. Associated minerals are calcite, in scalenohedral colorless crystals up to 2 mm in length, and rarely pyrite as very small octahedra usually grown on sulfur. Mammillary aggregates of pyrite, up to 3 mm across, have been also found. The occurrence of sulfur in the Monti Livornesi area and its association with some peculiar rocks (carbonated evaporites) deserves further geological studies.
The Calabrian-Peloritani Arc is a poorly studied area from a mineralogical perspective. Its current geological setting is the result of two different orogenic events, i.e., the Variscan and Alpine orogenies. Recent mineralogical researches allowed the finding of nice almandine crystals. More recently, in 2018, the possible occurrence of cordierite was noted by one of us (GB) during the paving of a road to the Santa Maria del Patire Abbey, close to the villages of Corigliano and Rossano Calabro, in the Cosenza Province. Further investigations allowed to localize the source of the stones used for the paving of the road, i.e., the Cava di Melis, located in the Longobucco municipality. Cordierite occurs as euhedral prismatic crystals, up to 3 cm in length and 1 cm across. The habit is prismatic, with wide basal pinacoids. Color ranges from light to dark green, sometimes with brownish hues. Some crystals are more or less altered in “pinite”. Cordierite is hosted in a microgranite dike cutting an altered granodiorite. Electron microprobe analysis confirmed that magnesium is dominant over iron. In addition to cordierite, other minerals found in this kind of occurrence are quartz, in bipyramidal phenocrysts, and rare pyrite crystals superficially altered in limonite.
MULLITE RICH IN
ALUMINUM AND COPPERER:
AN INTERESTING NOVELTY
FROM MOUNT CERVANDON
The mullite of Mount Cervandone has very different morphological characteristics compared to the usual mullite as it forms thin encrustations, very pale sky blue-greenish in color, lying on vitreous quartz.
This article re-proposes the historic and unique exceptional discovery of phenakite in the Beura quarries. It is the only discovery made in 1969 by F. Cantadore in very few specimens showing many crystals up to several millimeters in length. The uniqueness of the find is given by the quality of these samples since in Italy phenakite has never been found in relatively large specimens. At Beura two generations of phenakite crystals were observed: the first ones reach up to about two millimeters, have short prismatic habit consisting of hexagonal prisms terminated by well-developed rhombohedron faces whereas the second generation occur in elongated hexagonal prisms, whose dimensions reach up to several millimeters in length.
Many and beautiful specimens of hematite, as shiny tabular crystals have been known since the 19th century from the Monte Calvario quarry, near the town of Biancavilla (Sicily). These specimens are the best ever found in the Mt. Etna volcanic complex and can be considered among the classic mineral specimens from Sicily. At the end of the 20th century, the termination of the quarrying activity and the following environmental remediation precluded the collection of further important specimens of hematite.
This short note describes nice “iron roses” of hematite up to 2 centimeters in size collected in the Cairasca valley, within alpine-type fissures in erratic boulders occurring on the slopes located just north of the Varzo village.
Abstract ITALIAN MINERALOGICAL MAGAZINE