File:Amethyst-calcite in geode (Chihuahua, Mexico) 2 (31949858014).jpg
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Summary
[edit]DescriptionAmethyst-calcite in geode (Chihuahua, Mexico) 2 (31949858014).jpg |
Amethyst (= purple quartz) and calcite in a geode from Mexico. 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 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, has no cleavage, and has conchoidal fracture. Quartz can be any color: clear, white, gray, black, brown, pink, red, purple, blue, green, orange, etc. Purple quartz is called amethyst. The coloring agent for amethyst is not agreed upon. Some workers say that it is due to Fe+4 impurity, some say the impurity is Fe+3, and others say it is Mn. The amethyst shown above is lining the interior of a geode. Geodes are small to large, subspherical to irregularly-shaped, crystal-lined cavities in rocks. They form when water enters a void in a host rock and precipitates crystals. The most common geode-lining mineral is quartz. Photo gallery of quartz and amethyst <a href="http://www.mindat.org/gallery.php?min=3337" rel="nofollow">www.mindat.org/gallery.php?min=3337</a> and <a href="https://www.mindat.org/gallery.php?min=198" rel="nofollow">www.mindat.org/gallery.php?min=198</a> |
Date | |
Source | Amethyst-calcite in geode (Chihuahua, Mexico) 2 |
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@N05/31949858014 (archive). It was reviewed on 5 December 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
5 December 2019
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Date/Time | Thumbnail | Dimensions | User | Comment | |
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current | 02:04, 5 December 2019 | 2,382 × 1,938 (3.81 MB) | Ser Amantio di Nicolao (talk | contribs) | Transferred from Flickr via #flickr2commons |
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Camera manufacturer | NIKON CORPORATION |
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Camera model | NIKON D70s |
Exposure time | 1/60 sec (0.016666666666667) |
F-number | f/5.6 |
Date and time of data generation | 10:35, 5 May 2007 |
Lens focal length | 105 mm |
Orientation | Normal |
Horizontal resolution | 300 dpi |
Vertical resolution | 300 dpi |
Software used | Adobe Photoshop CS2 Macintosh |
File change date and time | 20:56, 8 February 2017 |
Y and C positioning | Co-sited |
Exposure Program | Not defined |
Exif version | 2.21 |
Date and time of digitizing | 10:35, 5 May 2007 |
Meaning of each component |
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Image compression mode | 4 |
APEX exposure bias | 0 |
Maximum land aperture | 4.9 APEX (f/5.46) |
Metering mode | Pattern |
Light source | Unknown |
Flash | Flash fired, strobe return light detected, auto mode |
DateTime subseconds | 10 |
DateTimeOriginal subseconds | 10 |
DateTimeDigitized subseconds | 10 |
Supported Flashpix version | 1 |
Color space | sRGB |
Sensing method | One-chip color area sensor |
File source | Digital still camera |
Scene type | A directly photographed image |
Custom image processing | Normal process |
Exposure mode | Auto exposure |
White balance | Auto white balance |
Digital zoom ratio | 1 |
Focal length in 35 mm film | 157 mm |
Scene capture type | Standard |
Scene control | None |
Contrast | Normal |
Saturation | Normal |
Sharpness | Normal |
Subject distance range | Unknown |
Supported Flashpix version | 1 |
Image width | 2,382 px |
Image height | 1,938 px |
Date metadata was last modified | 15:56, 8 February 2017 |