File:Kyanite 6.jpg
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Summary
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| Description |
English: Kyanite (15.4 centimeters across at its widest)
A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 5700 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates. The silicates are the most abundant and chemically complex group of minerals. All silicates have silica as the basis for their chemistry. "Silica" refers to SiO2 chemistry. The fundamental molecular unit of silica is one small silicon atom surrounded by four large oxygen atoms in the shape of a triangular pyramid - this is the silica tetrahedron - SiO4. Each oxygen atom is shared by two silicon atoms, so only half of the four oxygens "belong" to each silicon. The resulting formula for silica is thus SiO2, not SiO4. The simplest & most abundant silicate mineral in the Earth's crust is quartz (SiO2). All other silicates have silica + impurities. Many silicates have a significant percentage of aluminum (the aluminosilicates). The aluminum silicate mineral kyanite (Al2SiO5) is easy to identify. It has long, bladed crystals, a typically pale blue to dark blue coloration, and one cleavage plane. Kyanite is the best example of a mineral with variable hardness - it has a hardness of about 5 along the length of the blades and a hardness of about 7 across the blades. This mineral is usually encountered in some intermediate- to high-grade metamorphic rocks. Kyanite also occurs in some pegmatites (= very coarsely-crystalline, intrusive igneous rocks), as in the specimen shown here, with large kyanite crystals in quartz. Geologic unit & age: unrecorded/undisclosed Locality: unrecorded/undisclosed, but possibly (probably?) from a site in the Barra do Salinas Mining District, west of Coronel Murta, northeastern Minas Gerais State, eastern Brazil Photo gallery of kyanite: www.mindat.org/gallery.php?min=2303 |
| Date | |
| Source | https://www.flickr.com/photos/47445767@N05/39731147510/ |
| Author | James St. John |
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/39731147510. It was reviewed on 23 February 2023 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
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| current | 17:40, 23 February 2023 | | 3,336 × 1,420 (3.39 MB) | Ser Amantio di Nicolao (talk | contribs) | Uploaded a work by James St. John from https://www.flickr.com/photos/47445767@N05/39731147510/ with UploadWizard |
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