File:Precious opal in basalt (Honduras) 1.jpg
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Summary
[edit]DescriptionPrecious opal in basalt (Honduras) 1.jpg |
English: Precious opal ("black matrix opal") in Tertiary-aged vesicular basalt from Honduras.
The tiny spots of rainbow colors in this basalt sample (click once or twice on the picture to zoom in) are composed of precious opal. 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 called collloids that can be only be seen with a scanning electron microscope. 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, and 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 a play of colors - common opal usually has a wax-like luster and 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. Locality: unrecorded site in Honduras (possibly - probably? - from the Tablon Mine, near Erandique, southeastern Lempira Department, western Honduras) Photo gallery of opal: www.mindat.org/gallery.php?min=3004 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 | https://www.flickr.com/photos/47445767@N05/51069153073/ |
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@N05/51069153073. It was reviewed on 27 March 2021 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
27 March 2021
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current | 06:08, 27 March 2021 | 1,557 × 1,182 (1.65 MB) | Ser Amantio di Nicolao (talk | contribs) | Uploaded a work by James St. John from https://www.flickr.com/photos/47445767@N05/51069153073/ with UploadWizard |
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Camera manufacturer | Canon |
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Camera model | Canon PowerShot D10 |
Exposure time | 1/60 sec (0.016666666666667) |
F-number | f/10 |
ISO speed rating | 80 |
Date and time of data generation | 18:19, 24 March 2021 |
Lens focal length | 9.681 mm |
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 18.0 (Macintosh) |
File change date and time | 21:31, 24 March 2021 |
Y and C positioning | Co-sited |
Exif version | 2.21 |
Date and time of digitizing | 18:19, 24 March 2021 |
Meaning of each component |
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Image compression mode | 3 |
APEX shutter speed | 5.90625 |
APEX aperture | 6.65625 |
APEX exposure bias | −0.66666666666667 |
Maximum land aperture | 3.625 APEX (f/3.51) |
Metering mode | Pattern |
Flash | Flash fired, compulsory flash firing, red-eye reduction mode |
Supported Flashpix version | 1 |
Color space | sRGB |
Focal plane X resolution | 16,460.905349794 |
Focal plane Y resolution | 16,483.516483516 |
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 | Standard |
Lens used | 6.2-18.6 mm |
Date metadata was last modified | 17:31, 24 March 2021 |
Unique ID of original document | A6FE70E39B5374752FACEC114A6B4E34 |