File:Emerald-calcite-pyrite on carbonaceous shale (Muzo Hydrothermal Emerald Deposit; Muzo area, Boyaca, Colombia) (32688929206).jpg
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Emerald-calcite-pyrite on carbonaceous shale from Colombia. (.6 cm 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 5500 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). Beryl is a beryllium aluminosilicate mineral, Be3Al2(Si6O18). It has a nonmetallic luster, forms sharp, hexagonal crystals, is very hard (H=7.5 to 8), and can be any color. A frequently encountered color is pale bluish-green. Beryl has a glassy luster and no obvious cleavage Transparent beryls are gemstones. The gem name depends on the color: - deep green = emerald - bluish = aquamarine - pink = morganite - rich yellow = golden beryl - red = bixbite - yellowish-green to pale greenish = heliodor - clear/colorless = goshenite Emerald is green, chromiferous beryl. The emerald crystals shown above are associated with whitish calcite and brassy gold-colored pyrite. The dark-colored host rock is carbonaceous shale. The emerald, calcite, and pyrite are hydrothermal in origin. Geology: Muzo Hydrothermal Emerald Deposit, hosted in the Lower Carbonaceous Shale Member, Paja Formation, Aptian Stage, upper Lower Cretaceous Locality: unrecorded/undisclosed site in the Muzo area, west-southwest of Chiquinquira & north-northwest of Bogotá, western Boyaca Department, northwest-central Colombia Photo gallery of beryl: <a href="https://www.mindat.org/gallery.php?min=819" rel="noreferrer nofollow">www.mindat.org/gallery.php?min=819</a> Photo gallery of emerald: <a href="https://www.mindat.org/gallery.php?min=1375" rel="noreferrer nofollow">www.mindat.org/gallery.php?min=1375</a> |
| Date | |
| Source | Emerald-calcite-pyrite on carbonaceous shale (Muzo Hydrothermal Emerald Deposit; Muzo area, Boyaca, Colombia) |
| 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@N05/32688929206 (archive). It was reviewed on 30 November 2019 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 | 16:53, 30 November 2019 | | 993 × 1,094 (1.61 MB) | Ser Amantio di Nicolao (talk | contribs) | Transferred from Flickr via #flickr2commons |
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