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Geologic Occurrence of Molybdenite
Molybdenite occurs as isolated crystals, and foliated masses in granite, rhyolite, or pegmatite. Molybdenite is also found in rocks that have been altered by contact and hydrothermal metamorphism. Much of the commercially produced molybdenite occurs as disseminated crystals in porphyry copper deposits where it is produced as a byproduct mineral. Lesser amounts are produced at mines where molybdenite is the primary product.…
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Physical Properties of Molybdenite
Molybdenite has physical properties that often cause it to be confused with graphite. Both of these minerals are gray to silver in color, have a very low hardness, and occur in hexagonal crystals or foliated masses. Both minerals have a layered atomic structure with planes of extreme weakness. This gives them a slippery feel and makes them…
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What is Molybdenite?
Molybdenite is a rare mineral composed of molybdenum and sulfur, with a chemical composition of MoS2. It occurs in igneous and metamorphic rocks as gray hexagonal crystals and foliated masses with a metallic luster. Molybdenite is the most important ore of molybdenum and often contains minor amounts of rhenium which are often produced as a byproduct.
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Nevada Gemstones
A variety of gemstones have been found in Nevada, and the state is well-known for its opal. After Australia, some of the finest black opals in the world come from Virgin Valley, Nevada. The specimen shown here is a 9-millimeter faceted yellow fire opal of about 1.79 carats, cut from rough produced in Nevada. The state is also well-known…
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Louisiana Gemstones
Most people would not think of Louisiana as a “gemstone state.” However, it is the source of a unique variety of precious opal and a source for abundant amounts of “petrified palm wood.” The palm material found in the Catahoula Formation, a sedimentary rock unit deposited during Oligocene time, is so popular and well-known that the state…
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Maine Gemstones
The first commercial gemstone mine in the United States that was operated by miners who were not Native Americans was at Mount Mica, Maine. There a large deposit of tourmaline was discovered by children in 1820. Two years later a mine was opened and it yielded thousands of carats of gem-quality tourmaline crystals. Since then the pegmatite deposits of…
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Idaho Gemstones
Idaho’s nickname is “The Gem State.” It has a long history of producing a variety of gem materials. The most important gems produced to date have been star garnet and opal. Notable amounts of jade, topaz, zircon, and tourmaline have also been found in Idaho. Agate, jasper, and petrified wood in many colors and patterns have been found and produced from small deposits throughout the state.
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Arkansas Gemstones
The most popular gemstone locality in Arkansas is Crater of Diamonds State Park, where anyone can pay a fee, look for diamonds, and keep any that are found. The site is an operating state park, and visitors usually find hundreds of small diamonds every year. There are several other fee mining areas in the state where you…
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Colorado Gemstones
Many different gemstones are produced in Colorado. These include aquamarine, amazonite, garnet, topaz, tourmaline, lapis lazuli, quartz, smoky quartz, rhodochrosite, rose quartz, amethyst, turquoise, peridot, sapphire, zircon, agate, and jasper. A rough diamond from Colorado was cut into a 16.87-carat stone. It is the largest cut diamond ever produced from United States rough. Aquamarine is the state gemstone of Colorado, and it is mostly found at high elevations on Antero…
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Montana Gemstones
Montana’s most popular gemstone product is sapphire. Yogo Gulch sapphires have been famous for over 100 years, and the production of sapphires in Montana continues today. Sapphires are produced from both rock and alluvial deposits. They occur in a wide range of colors which include blue, blue-green, green, pink, pale red, purple, yellow, and orange (colors…