Minerals

Granite is an igneous rock that is composed of four minerals. These minerals are quartz, feldspar, mica, and usually hornblende. Granite forms as magma cools far under the earth's surface. Because it hardens deep underground it cools very slowly. This...
Serpentine: A family of silicate minerals rich in magnesium and water, derived from low-temperature alteration or metamorphism of the minerals in ultramafic rocks (intrusive igneous rocks very rich in iron and magnesium and with much less silicon and...
Sterling silver is the standard of quality for articles containing 92.5% silver and 7.5% copper (and/or other alloys).
The fineness of jewelry gold is stated as the number of parts in twenty-four that are gold. Thus, 24 karat gold is pure gold; 12 K would be an alloy that is half gold and half copper or other metals.  
White gold was originally developed to imitate platinum, and is usually an alloy containing 25% nickel and zinc. If stamped 18 karat, it would be 75% pure gold.  
For statistical information about mineral commodities, visit the USGS Commodity Statistics and Information website.  
Mineral elements provide the color in fireworks. Barium produces bright greens; strontium yields deep reds; copper produces blues; and sodium yields yellow. Other colors can be made by mixing elements; strontium and sodium produce brilliant orange;...
The following USGS products will be helpful in determining the background levels of various elements in soils and other surficial materials:Professional Paper 1270. Element Concentrations in Soils and Other Surficial Materials of the Conterminous United...
The USGS Field Records Library in Denver, Colorado, has an extensive collection of materials. Many of the field records are online at http://www.cr.usgs.gov/. You may contact them at: USGS Field Records LibraryBox 25046, MS 914Denver Federal CenterDenver...
Minerals must be mined from the ground, either by surface, underground, or drilling methods. Sand and gravel is usually mined in surface pits or rock is crushed to size, gold is mined in surface pits, underground mines, and in streams and rivers.