File:Pink banded opal (Western Australia) 3 (30792541574).jpg
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Summary
[edit]DescriptionPink banded opal (Western Australia) 3 (30792541574).jpg |
Pink banded opal from Western Australia. (photo by Ljubomir Ristestki) 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 4900 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. Opal is hydrous silica (SiO2·nH2O). Technically, opal is not a mineral because it lacks a crystalline structure. Opal is supposed to be called a mineraloid. Opal is made up of extremely tiny spheres (colloids - <a href="https://www.uwgb.edu/dutchs/acstalks/acscolor/OPALSPHR.jpg" rel="nofollow">www.uwgb.edu/dutchs/acstalks/acscolor/OPALSPHR.jpg</a>) that can be seen with a scanning electron microscope (SEM). Gem-quality opal, or precious opal, has a wonderful rainbow play of colors (opalescence). This play of color is the result of light being diffracted by planes of voids between large areas of regularly packed, same-sized opal colloids. Different opalescent colors are produced by colloids of differing sizes. If individual colloids are larger than 140 x 10-6 mm in size, purple & blue & green colors are produced. Once colloids get as large as about 240 x 10-6 mm, red color is seen (Carr et al., 1979). Not all opals have the famous play of colors, however. Common opal has a wax-like luster & is often milky whitish with no visible color play at all. Opal is moderately hard (H = 5 to 6), has a white streak, and has conchoidal fracture. Several groups of organisms make skeletons of opaline silica, for example hexactinellid sponges, diatoms, radiolarians, silicoflagellates, and ebridians. Some organisms incorporate opal into their tissues, for example horsetails/scouring rushes and sawgrass. Sometimes, fossils are preserved in opal or precious opal. Locality: stratiform opal occurrence at an undisclosed site attributed to the Gascoyne region east of Carnarvon, Western Australia Photo gallery of opal: <a href="http://www.mindat.org/gallery.php?min=3004" rel="nofollow">www.mindat.org/gallery.php?min=3004</a> Reference cited: Carr et al. (1979) - Andamooka opal fields: the geology of the precious stones field and the results of the subsidised mining program. Geological Survey of South Australia Department of Mines and Energy Report of Investigations 51. 68 pp. |
Date | |
Source | Pink banded opal (Western Australia) 3 |
Author | James St. John |
Camera location | 39° 58′ 29.97″ N, 82° 47′ 37.52″ W ![]() ![]() | View this and other nearby images on: OpenStreetMap | ![]() |
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/30792541574 (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. |
30 November 2019
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current | 16:53, 30 November 2019 | ![]() | 2,141 × 2,471 (2.47 MB) | Ser Amantio di Nicolao (talk | contribs) | Transferred from Flickr via #flickr2commons |
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Camera manufacturer | Apple |
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Camera model | iPhone 6s Plus |
Exposure time | 1/490 sec (0.0020408163265306) |
F-number | f/2.2 |
ISO speed rating | 25 |
Date and time of data generation | 21:40, 13 December 2016 |
Lens focal length | 4.15 mm |
Latitude | 39° 58′ 29.97″ N |
Longitude | 82° 47′ 37.52″ W |
Altitude | 291.015 meters above sea level |
Width | 3,024 px |
Height | 4,032 px |
Bits per component |
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Pixel composition | RGB |
Orientation | Normal |
Number of components | 3 |
Horizontal resolution | 72 dpi |
Vertical resolution | 72 dpi |
Software used | Adobe Photoshop Elements 13.0 (Macintosh) |
File change date and time | 23:29, 13 December 2016 |
Y and C positioning | Centered |
Exposure Program | Normal program |
Exif version | 2.21 |
Date and time of digitizing | 21:40, 13 December 2016 |
Meaning of each component |
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APEX shutter speed | 8.93580131209 |
APEX aperture | 2.2750071245369 |
APEX brightness | 8.6325581395349 |
APEX exposure bias | 0 |
Metering mode | Pattern |
Flash | Flash fired, compulsory flash firing |
DateTimeOriginal subseconds | 398 |
DateTimeDigitized subseconds | 398 |
Supported Flashpix version | 1 |
Color space | sRGB |
Sensing method | One-chip color area sensor |
Scene type | A directly photographed image |
Exposure mode | Auto exposure |
White balance | Auto white balance |
Focal length in 35 mm film | 29 mm |
Scene capture type | Standard |
GPS time (atomic clock) | 02:40 |
Speed unit | Kilometers per hour |
Speed of GPS receiver | 0 |
Reference for direction of image | True direction |
Direction of image | 281.57092198582 |
Reference for bearing of destination | True direction |
Bearing of destination | 281.57092198582 |
GPS date | 14 December 2016 |
Lens used | iPhone 6s Plus back camera 4.15mm f/2.2 |
Date metadata was last modified | 18:29, 13 December 2016 |
Unique ID of original document | C817B4CF8801C3E7D4FBD1DF6FDFF2C0 |