File:Gold nugget (Australia) 4 (16848647509).jpg
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[edit]DescriptionGold nugget (Australia) 4 (16848647509).jpg |
Gold nugget from Australia. (public display, Field Museum of Natural History, Chicago, Illinois, USA). The Australian rock shown above is a large, nearly four pound mass of gold. The irregularly-distributed, smoothly sculpted surfaces indicate that this is likely a fluvial gold cobble - in other words, it appears to be from a placer deposit. Gold is a metal. Metallic, semimetallic (metalloid), and nonmetallic elements are known in their native state as minerals. 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. As of the year 2018, there are around 4500 named and described terrestrial 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. Elements are fundamental substances of matter - matter that is composed of the same types of atoms. At present, 118 elements are known. Of these, 94 occur naturally on Earth (hydrogen to plutonium). Gold is a native element in nature. To find a native element, it must be relatively non-reactive and there must be some concentration process. Most of these occur in rocks & minerals, although some occur in very small, trace amounts. Only some elements occur in their native elemental state as minerals. Gold is very rare in crustal rocks - it averages about 5 ppb (parts per billion). Where gold has been concentrated, it occurs as wires, dendritic crystals, twisted sheets, octahedral crystals, and variably-shaped nuggets. It most commonly occurs in hydrothermal quartz veins, disseminated in some contact- & hydrothermal- metamorphic rocks, and in placer deposits. Placers are concentrations of heavy minerals in stream gravels or in cracks on bedrock-floored streams. Gold has a high specific gravity (about 19), so it easily accumulates in placer deposits. Its high density allows prospectors to readily collect placer gold by panning. Gold (Au) is the most prestigious metal known, but it's not the most valuable. Gold is the only metal that has a deep, rich, metallic yellow color. |
Date | |
Source | https://www.flickr.com/photos/jsjgeology/16848647509/ |
Author | James St. John |
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This image was originally posted to Flickr by jsj1771 at https://www.flickr.com/photos/47445767@N05/16848647509. It was reviewed on 6 April 2015 by FlickreviewR and was confirmed to be licensed under the terms of the cc-by-2.0. |
6 April 2015
Reference
[edit]www-acc.esa.int European Space Agency 2018
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current | 20:35, 6 April 2015 | 3,531 × 2,278 (2.8 MB) | Jacopo Werther (talk | contribs) | Transferred from Flickr via Flickr2Commons |
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Camera manufacturer | Canon |
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Camera model | Canon PowerShot D10 |
Exposure time | 1/4 sec (0.25) |
F-number | f/4.5 |
ISO speed rating | 320 |
Date and time of data generation | 16:29, 21 August 2010 |
Lens focal length | 14.303 mm |
Width | 4,000 px |
Height | 3,000 px |
Bits per component |
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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 | 18:38, 4 April 2015 |
Y and C positioning | Co-sited |
Exif version | 2.21 |
Date and time of digitizing | 16:29, 21 August 2010 |
Meaning of each component |
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Image compression mode | 3 |
APEX shutter speed | 2 |
APEX aperture | 4.34375 |
APEX exposure bias | 0 |
Maximum land aperture | 4.34375 APEX (f/4.51) |
Metering mode | Pattern |
Flash | Flash did not fire, compulsory flash suppression |
Supported Flashpix version | 1 |
Color space | sRGB |
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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 | Auto 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 | 14:38, 4 April 2015 |
Unique ID of original document | C5355AFE97F788F5016FBE715B428B96 |
IIM version | 17,259 |