Barite

Barite is a major source of barium (Ba). Since it also contains the sulfate group, SO4, it is classified as a sulfate. Many sulfates form from the weathering of other minerals. They are often associated with ore deposits.

Barite

Barite is a major source of barium (Ba). Since it also contains the sulfate group, SO4, it is classified as a sulfate. Many sulfates form from the weathering of other minerals. They are often associated with ore deposits.

Barite

Barite, Berthierite, Calcite, and Quartz. Barite is the major cource of barium (Ba) used to manufacture paint pigments, color fireworks green, and make barium "milkshakes" that highlight patients' digestive tracts for xray imaging.

Brochanite

Crocoite

This crocoite is a great example of what gives minerals their color. Some minerals are always the same color. Others, such as quartz, vary in color depending on impurities, inclusions, or defects in their atomic structure. Crocoite's color, always orange or reddish-orange, comes from chromium, a valuable metal first extracted from this rare mineral. The best crocoite in the world is found in Tasmania, where it was once mined for lead.

Gypsum

The chemical composition of gypsum is CaSO4.2H2O. Pure gypsum is a whitish clear mineral. The yellowish cast of this specimen is caused by sulfur impurities in the crystals.

Gypsum

Giant gypsum crystals grew from a water solution that filled a limestone cave located about 244 m (800 ft) underground in Mexico's state of Chihuahua. In some passageways, the bladelike crystals form a veritable corridor of swords. Miners extending a tunnel in Maravilla Silver Mine accidentally discovered this cave of swords in the early 1900s.

Gypsum

Fed by a mineral-rich solution that seeped through rock, this specimen grew from the wall of a cave. The "ram's horns" curved as some crystal strands grew faster than others.

Gypsum

Gypsum

Gypsum (variety: Selenite)

These chisel-shaped crystals grew in a cavity in limestone filled with water rich in dissolved minerals. Large deposits of gypsum are mined to make plaster of Paris, wallboard, alabaster carvings, and stucco.

Gypsum Flower

The curling "horns" on this specimen result from some of the crystals in the strand growing faster than others.

Wulfenite

Both these butterscotch-colored crystals and the darker orange crystals are wulfenite. Light interacts with impurities of chromium to color wulfenite shades of yellow, orange, and red. Wulfenite commonly grows as plate-like crystals but also assumes other shapes. It is prized for showy crystals and has been mined for lead.

Wulfenite

Light interacts with impurities of chromium to color wulfenite shades of yellow, orange, and red. Wulfenite commonly grows as plate-like crystals but also assumes other shapes. It is prized for showy crystals and has been mined for lead.