File:Fluorite fluorescing (England) 2.jpg
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| Description |
English: Fluorite from England. (public display, Carnegie Museum of Natural History, Pittsburgh, Pennsylvania, USA)
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 about 5400 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 halides are the "salt minerals", and have one or more of the following anions: Cl-, F-, I-, Br-. Fluorite is a calcium fluoride mineral (CaF2). The most diagnostic physical property of fluorite is its hardness (H≡4). Fluorite typically forms cubic crystals and, when broken, displays four cleavage planes (also quite diagnostic). When broken under controlled conditions, the broken pieces of fluorite form double pyramids. Fluorite is a good example of a mineral that can be any color. Common fluorite colors include clear, purple, blue, green, yellow, orange, and brown. The stereotypical color for fluorite is purple. Purple is the color fluorite "should be". A mineral collector doesn't have fluorite unless it's a purple fluorite (!). Fluorite occurs in association with some active volcanoes. HF emitted from volcanoes can react with Ca-bearing rocks to form fluorite crystals. Many hydrothermal veins contain fluorite. Much fluorite also occurs in the southern Illinois area (Mississippi Valley-type deposits). Some fluorite samples will glow (fluoresce) under ultraviolet black light (UV). In fact, fluorescence was named after the mineral fluorite. The specimen shown above does fluoresce (see the next 2 photos in this album or photostream). Why do some minerals fluoresce under UV light? When short-wavelength UV radiation, long-wavelength UV radiation, or x-rays bombard atoms, electron excitation occurs. The electrons do not remain in an energetically excited state - they quickly give off energy and resume their normal energy levels. If the electron energy release is in the visible spectrum of light, a mineral glows, or fluoresces. Photo gallery of fluorite: www.mindat.org/gallery.php?min=1576 |
| Date | |
| Source | https://www.flickr.com/photos/47445767@N05/30525591894/ |
| 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@N05/30525591894 (archive). It was reviewed on 22 December 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
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| current | 18:25, 22 December 2019 | | 2,020 × 2,408 (3.47 MB) | Ser Amantio di Nicolao (talk | contribs) | User created page with UploadWizard |
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