File:Emeralds in pegmatitic granite 6 (37992558594).jpg
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[edit]DescriptionEmeralds in pegmatitic granite 6 (37992558594).jpg |
Emeralds in pegmatitic granite 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 green crystals shown here are emeralds in pegmatitic granite, which is a very coarsely-crystalline, intrusive igneous rock. In the matrix, the glassy, medium gray-colored material is quartz (SiO2 - silica), a common and essential mineral in this granite. The light, cream-colored material is potassium feldspar (KAlSi3O8 - potassium aluminosilicate), also a common and essential mineral in this lithology. The Pegmatites are usually form during the final phases of crystallization of a cooling pluton. The large crystal size in pegmatites is due to cooling of a relatively water-rich magma. The magma from which pegmatites form is usually enriched in noncompatible elements. This results in the formation of scarce minerals, such as beryl (= the emeralds seen here) and tourmaline (= the small black sticks and the black radiating cluster; click on the photo to zoom in and look around). 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 | Emeralds in pegmatitic granite 6 |
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@N05/37992558594 (archive). It was reviewed on 12 November 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
12 November 2019
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current | 04:16, 12 November 2019 | 3,801 × 2,792 (5.22 MB) | Ser Amantio di Nicolao (talk | contribs) | Transferred from Flickr via #flickr2commons |
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Camera manufacturer | Canon |
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Camera model | Canon PowerShot D10 |
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F-number | f/9 |
ISO speed rating | 80 |
Date and time of data generation | 15:07, 17 November 2017 |
Lens focal length | 8.295 mm |
Image title | |
Width | 4,000 px |
Height | 3,000 px |
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Pixel composition | RGB |
Orientation | Normal |
Number of components | 3 |
Horizontal resolution | 180 dpi |
Vertical resolution | 180 dpi |
Software used | Adobe Photoshop Elements 13.0 (Macintosh) |
File change date and time | 17:47, 28 November 2017 |
Y and C positioning | Co-sited |
Exif version | 2.21 |
Date and time of digitizing | 15:07, 17 November 2017 |
Meaning of each component |
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Image compression mode | 3 |
APEX shutter speed | 5.90625 |
APEX aperture | 6.34375 |
APEX exposure bias | −0.66666666666667 |
Maximum land aperture | 3.34375 APEX (f/3.19) |
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Focal plane resolution unit | inches |
Sensing method | One-chip color area sensor |
File source | Digital still camera |
Custom image processing | Normal process |
Exposure mode | Manual exposure |
White balance | Auto white balance |
Digital zoom ratio | 1 |
Scene capture type | Portrait |
Lens used | 6.2-18.6 mm |
Date metadata was last modified | 12:47, 28 November 2017 |
Unique ID of original document | 03D1857692B748125EF21DCC3B411472 |
IIM version | 29,735 |