-
Physical Properties of Hematite
Hematite has an extremely variable appearance. Its luster can range from earthy to submetallic to metallic. Its color ranges include red to brown and black to gray to silver. It occurs in many forms that include micaceous, massive, crystalline, botryoidal, fibrous, oolitic, and others. Even though hematite has a highly variable appearance, it always produces…
-
What is Hematite?
Hematite is one of the most abundant minerals on Earth’s surface and in the shallow crust. It is an iron oxide with a chemical composition of Fe2O3. It is a common rock-forming mineral found in sedimentary, metamorphic, and igneous rocks at locations throughout the world. Hematite is the most important ore of iron. Although it was once mined at thousands of locations around the world,…
-
Uses of Molybdenum Metal
Molybdenite is the primary ore of molybdenum metal, which is an extremely important metal for making specialty alloys. Small amounts of molybdenum added to steel and other alloys can significantly increase their toughness, heat resistance, hardness, strength, and resistance to corrosion. Molybdenum is an important ingredient in making stainless steel, alloy steels, and a variety…
-
Lubricant Uses of Molybdenite
Molybdenite has a layered atomic structure in which a sheet of molybdenum atoms is sandwiched between two sheets of sulfur. The bonds between the molybdenum and sulfur atoms are very strong. These S-Mo-S layers are stacked one on top of another, but the bonds between the layers are very weak. The bonds between the layers…
-
Molybdenite as an Ore of Rhenium
With an average crustal abundance of less than one part per billion, rhenium is one of the rarest elements in Earth’s crust. Most of the world’s known rhenium resource exists within the mineral molybdenite, substituting for molybdenum atoms in the mineral’s crystal lattice. Rhenium has one of the most surprising and indirect methods of production…
-
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.…
-
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…
-
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.
-
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…
-
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…