File:Gold and quartz (Main Ledge, 3050 Level, Homestake Mine, Lead, Black Hills, South Dakota, USA) 2.jpg
Original file (3,008 × 2,000 pixels, file size: 4.69 MB, MIME type: image/jpeg)
Captions
Summary
[edit]DescriptionGold and quartz (Main Ledge, 3050 Level, Homestake Mine, Lead, Black Hills, South Dakota, USA) 2.jpg |
English: Gold and quartz from the Precambrian of South Dakota, USA. (SDSMT 5080, South Dakota School of Mines and Technology Museum of Geology, Rapid City, South Dakota, USA)
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. Elements are fundamental substances of matter - matter that is composed of the same types of atoms. At present, 118 elements are known (four of them are still unnamed). Of these, 98 occur naturally on Earth (hydrogen to californium). 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. To find a native element in nature, it must be relatively non-reactive and there must be some concentration process. Metallic, semimetallic (metalloid), and nonmetallic elements are known in their native state as minerals. 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. Almost all other metals are silvery-colored. 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. In addition to its high density, gold has a high melting point (over 1000º C). Gold is also relatively soft - about 2.5 to 3 on the Mohs Hardness Scale. The use of pure gold or high-purity gold in jewelry is not desirable as it easily gets scratched. The addition of other metals to gold to increase the hardness also alters the unique color of gold. Gold jewelry made & sold in America doesn’t have the gorgeous rich color of high-purity gold. The largest gold mine in the Americas was the long-lived Homestake Mine in the town of Lead (pronounced “Leed”), South Dakota, USA. Located in the Lead Window of the northern Black Hills Uplift in western South Dakota, the Homestake Mine produced about 40 million ounces of gold. The gold at Homestake is almost exclusively confined to the Homestake Formation, a Paleoproterozoic (~1.9-2.0 billion years) sedimentary unit that originally consisted of interbedded Mg-rich siderite iron formation and marlstones. The Homestake Formation has been strongly deformed & multiply metamorphosed, and many of the original rocks were converted to greenschists (cummingtonite schists). The gold has been interpreted as having been originally deposited with the iron formation sediments by seafloor volcanogenic exahalative processes. Slight metamorphic gold mobilization and tight structural folding has resulted in the formation of auriferous greenschist pods along fold axes. Locality: Main Ledge, 3050 Level, Homestake Mine, Lead, northern Black Hills, western South Dakota, USA Photo gallery of gold: www.mindat.org/gallery.php?min=1720 |
Date | |
Source | https://www.flickr.com/photos/47445767@N05/17027399647/ |
Author | James St. John |
Licensing
[edit]- You are free:
- to share – to copy, distribute and transmit the work
- to remix – to adapt the work
- Under the following conditions:
- attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/17027399647 (archive). It was reviewed on 10 March 2020 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
10 March 2020
File history
Click on a date/time to view the file as it appeared at that time.
Date/Time | Thumbnail | Dimensions | User | Comment | |
---|---|---|---|---|---|
current | 14:51, 10 March 2020 | 3,008 × 2,000 (4.69 MB) | Ser Amantio di Nicolao (talk | contribs) | Uploaded a work by James St. John from https://www.flickr.com/photos/47445767@N05/17027399647/ with UploadWizard |
You cannot overwrite this file.
File usage on Commons
There are no pages that use this file.
Metadata
This file contains additional information such as Exif metadata which may have been added by the digital camera, scanner, or software program used to create or digitize it. If the file has been modified from its original state, some details such as the timestamp may not fully reflect those of the original file. The timestamp is only as accurate as the clock in the camera, and it may be completely wrong.
Camera manufacturer | NIKON CORPORATION |
---|---|
Camera model | NIKON D70s |
Exposure time | 1/60 sec (0.016666666666667) |
F-number | f/5.6 |
ISO speed rating | 400 |
Date and time of data generation | 11:50, 18 August 2010 |
Lens focal length | 200 mm |
Width | 3,008 px |
Height | 2,000 px |
Bits per component |
|
Pixel composition | RGB |
Orientation | Normal |
Number of components | 3 |
Horizontal resolution | 300 dpi |
Vertical resolution | 300 dpi |
Software used | Adobe Photoshop Elements 16.0 (Macintosh) |
File change date and time | 01:51, 11 July 2019 |
Y and C positioning | Co-sited |
Exposure Program | Not defined |
Exif version | 2.21 |
Date and time of digitizing | 11:50, 18 August 2010 |
Meaning of each component |
|
Image compression mode | 4 |
APEX shutter speed | 5.906891 |
APEX aperture | 4.970854 |
APEX exposure bias | 0 |
Maximum land aperture | 5 APEX (f/5.66) |
Metering mode | Pattern |
Light source | Unknown |
Flash | Flash fired, strobe return light detected, auto mode |
DateTime subseconds | 20 |
DateTimeOriginal subseconds | 20 |
DateTimeDigitized subseconds | 20 |
Supported Flashpix version | 1 |
Color space | sRGB |
Sensing method | One-chip color area sensor |
File source | Digital still camera |
Scene type | A directly photographed image |
Custom image processing | Normal process |
Exposure mode | Auto exposure |
White balance | Auto white balance |
Digital zoom ratio | 1 |
Focal length in 35 mm film | 300 mm |
Scene capture type | Standard |
Scene control | None |
Contrast | Normal |
Saturation | Normal |
Sharpness | Normal |
Subject distance range | Unknown |
Serial number of camera | 200638ad |
Lens used | 18.0-200.0 mm f/3.5-5.6 |
Date metadata was last modified | 21:51, 10 July 2019 |
Unique ID of original document | DDCD58BB580A7582FB70DBDC4FA3D4E9 |