File:Quartz (Dalnegorsk Skarn Deposit, Late Cretaceous, 70-90 Ma; Dalnegorsk, Russia) 1.jpg
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| Description |
English: Quartz crystal from the Cretaceous of Russia.
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 6000 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). Quartz (silicon dioxide/silica - SiO2) is the most common mineral in the Earth's crust. It is composed of the two most abundant elements in the crust - oxygen and silicon. It has a glassy, nonmetallic luster, is commonly clearish to whitish to grayish in color, has a white streak, is quite hard (H≡7), forms hexagonal crystals (even though it's in the trigonal crystal system), has no cleavage, and has conchoidal fracture. Quartz can be any color: clear, white, gray, black, brown, pink, red, purple, blue, green, orange, etc. The hexagonal crystal of quartz seen here comes from the famous Dalnegorsk Skarn Deposit in Russia. The deposit consists of mineral-filled solution cavities in Triassic limestones that have been intruded by Late Cretaceous granodiorites. The skarn zone itself has been intruded by 64 Ma granite. Geologic unit: Dalnegorsk Skarn Deposit, Late Cretaceous, 70-90 Ma Locality: unrecorded / undisclosed mine in the Dalnegorsk area, southern Sikhote-Alin Mountains, Maritime Region ("Primorskiy Kray"), far-eastern Russia |
| Date | |
| Source | https://www.flickr.com/photos/47445767@N05/53679335892/ |
| 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@N05/53679335892. It was reviewed on 26 April 2024 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
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| current | 21:00, 26 April 2024 | | 2,157 × 1,835 (2.17 MB) | Ser Amantio di Nicolao (talk | contribs) | Uploaded a work by James St. John from https://www.flickr.com/photos/47445767@N05/53679335892/ with UploadWizard |
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