File:Agate- & quartz-lined geode 4 (32632020771).jpg
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DescriptionAgate- & quartz-lined geode 4 (32632020771).jpg |
Agate and quartz lining a geode. (public display, Cleveland Museum of Natural History, Ohio, USA) Shown above is 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. This geode is bordered by dark-colored & bluish-gray & whitish agate. "Agate" is a rockhound/collector term for irregularly concentric layers of microcrystalline, fibrous quartz (chalcedony - SiO2). Agate is quartz. Geode info. from the Field Museum of Natural History (Chicago, Illinois, USA): "Geodes are hollow, subspherical bodies, ranging from an inch or two to a foot or more in diameter. Most geodes occur in limestones, rarely in shales. They have an outer chalcedonic silica layer which is separated from the enclosing limestone matrix by a thin clay film. The inner surface of the chalcedonic layer is usually lined with inward projecting quartz crystals, though in many geodes drusy coatings of calcite and dolomite occur commonly. Of less common occurrence, are crystals of magnetite, pyrite, sphalerite, and a few other such minor and rarer constituents. The mode of origin of geodes in sedimentary rocks is but imperfectly understood. That geodes originate in an initial cavity, such as the unfilled space within a fossil, is well recognized, but whether such a cavity is a necessary prerequisite is open to question; geodes may originate in cavities formed by solution. Many geodes show evidence of expansion, apparently resulting from pressure. A notable example of this singular phenomenon of expansion of the growing geodes is the "exploding bomb" structure. " |
Date | |
Source | Agate- & quartz-lined geode 4 |
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@N05/32632020771 (archive). It was reviewed on 10 October 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
10 October 2019
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Date/Time | Thumbnail | Dimensions | User | Comment | |
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current | 07:12, 10 October 2019 | 2,092 × 1,918 (2.01 MB) | Ser Amantio di Nicolao (talk | contribs) | Transferred from Flickr via #flickr2commons |
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Exposure time | 1/30 sec (0.033333333333333) |
F-number | f/4.5 |
Date and time of data generation | 13:19, 22 July 2006 |
Lens focal length | 48 mm |
Orientation | Normal |
Horizontal resolution | 300 dpi |
Vertical resolution | 300 dpi |
Software used | Adobe Photoshop CS2 Macintosh |
File change date and time | 20:18, 6 February 2017 |
Y and C positioning | Co-sited |
Exposure Program | Not defined |
Exif version | 2.21 |
Date and time of digitizing | 13:19, 22 July 2006 |
Meaning of each component |
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Image compression mode | 4 |
APEX exposure bias | 0 |
Maximum land aperture | 4.3 APEX (f/4.44) |
Metering mode | Pattern |
Light source | Unknown |
Flash | Flash did not fire |
DateTime subseconds | 20 |
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DateTimeDigitized subseconds | 20 |
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Color space | sRGB |
Sensing method | One-chip color area sensor |
File source | Digital still camera |
Scene type | A directly photographed image |
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Digital zoom ratio | 1 |
Focal length in 35 mm film | 72 mm |
Scene capture type | Standard |
Scene control | None |
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Sharpness | Normal |
Subject distance range | Unknown |
Supported Flashpix version | 1 |
Image width | 2,092 px |
Image height | 1,918 px |
Date metadata was last modified | 15:18, 6 February 2017 |
IIM version | 2 |