Monoclinic

Monoclinic

Found with pentlandite in basic igneous rocks, veins, and metamorphic rocks, this mineral is mined for its associated nickel, copper, and platinum. It is recognized by its massive nature, bronze color, and magnetism. The name comes from the Greek word meaning "reddish."

A rare mineral usually associated with realgar, orpiment is characterized by its yellow color. It was formerly used as pigment, but discontinued due to its arsenic content. Its name comes from the Latin auripigmentum meaning "golden paint," in allusion to its color and because the substance was supposed to contain gold.

Once of the most important copper-ore minerals, chalcocite occurs as a secondary mineral in or near the oxidized zone of copper sulfide deposits. Under surface conditions, the primary copper sulfides are oxidized, the soluble sulfates formed move downward reacting to form chalcocite, and thus, enriching the ore in copper. The water table is the lower limit of the zone of oxidation and here a "chalcocite blanket" may form.

This is the most common mineral containing arsenic and is the principal source of arsenic. It occurs in high temperature gold-quartz or tin hydrothermal veins, pegmatites, and metamorphic rocks. Its name is a contraction of the older term: arsenical pyrite.

The name refers to the high-temperature form of silver sulfide, only stable over 177° C. The mineral acanthite is the stable form of this mineral below 177° C. This is the tarnish that forms on sterling silver. An important ore of silver, it is found in moderately low-temperature hydrothermal sulfide veins and in zones of secondary enrichment. Its name comes from the Latin "argentum" meaning “silver.”

Discovered in 1825 in Cornwall, England, this mineral is named for mineralogist Robert Jameson (1774-1854) of Edinburgh. It is recognized by its characteristic fibrous appearance and is found in ore veins of low to moderate temperatures.

The most common of the sulfate minerals, this mineral is found in marine evaporites, in caves, fumaroles, and in the oxidized zones of sulfide deposits. When formed as clear crystals, it is referred to as selenite. The fibrous variety is known as satin spar and also forms in "roses." It is used chiefly for the production of plaster of Paris, wallboard, and fertilizer. It is named in antiquity from the Greek, meaning “plaster.”

This mineral has a bright hyacinth-red color and an orange-yellow streak. It is commonly found as crystals, which are translucent with an adamantine luster. It is not abundant enough to be of commercial value, but it is of historic interest because the element chromium was first discovered in crocoite. Its name is from the Greek word meaning "saffron," in allusion to the color.

Its dark color, one direction of perfect cleavage, and high specific gravity distinguish this mineral from others. It is a comparatively rare mineral found usually in pegmatites and high temperature quartz veins. It is a chief ore of tungsten, which is used as a hardening metal in the manufacture of high-speed tools such as carbides.

Discovered in 1827 in Germany, this mineral was named in allusion to the manganese content, though it is a minor ore of manganese. It forms in low temperature hydrothermal or hot spring deposits and is found associated with other manganese oxides.