Betekhtinite and Calcite Crystal

Betekhtinite is a sulfide mineral seen here as a black crytalline aggregate with a white calcite crystal.

Cinnabar with mercury

Cinnabar is a red mercury sulfide, the common ore of mercury. It has been mined for its use as a pigment as well as for the mercury content. The mining and refining of cinnabar for mercury is hazardous because of mercury's high toxicity, which can lead to mercury poisoning.

Dyscrasite

This silver-white mineral tarnishes yellow or black when exposed to light due to the silver in its composition.

Galena

Galena

Galena's shape reflects the cubic arrangement of its atoms. Galena is the major source of lead.

Galena

Marcasite

Crystal formations such as this grow out of mineral-rich solutions in spacious rock cavities. When the solution becomes saturated, crystals begin to form on rock walls, on other crystals, or even on particles of dust. They grow quickly or slowly--or stop--depending on changes in temperature and the concentration of the solution. Marcasite forms from iron and sulfur to make crystals with a chemical composition of FeS2. Note how the size of the forming crystals grew larger with each round of formation in this specimen.

Millerite

Millerite is classified as a sulfide. All sulfides have sulfur, S, combined with a metal. Together with another class of sulfur-containing minerals, the sulfosalts, sulfides make up the majority of the important ore minerals.

Millerite with hematite

The delicate tuft of needlelike millerite crystals grew to fill a pocket in hematite, creating this world-famous specimen.

Pyrite

Pyrite

Different growth conditions result in different external shapes of pyrite. This is despite the fact that they are all made up of iron and sulfur atoms linked in the same cubic pattern. The three common shapes of pyrite are: pyritohedron, octahedron, and cube. Cubes tend to grow under low temperatures from solutions with low concentrations of iron and sulfur. Octahedrons and pyritohedrons grow under higher temperatures and more concentrated solutions.

Pyrite

Different growth conditions result in different external shapes of pyrite. This is despite the fact that they are all made up of iron and sulfur atoms linked in the same cubic pattern. The three common shapes of pyrite are: pyritohedron, octahedron, and cube. Cubes tend to grow under low temperatures from solutions with low concentrations of iron and sulfur. Octahedrons and pyritohedrons grow under higher temperatures and more concentrated solutions.

Pyrite (Pyritohedron)

Pyrite (with Quartz)

Pyrite cubes

These pyrite crystals formed exactly as you see them. Their cubic shape mirrors the internal cubic arrangement of iron and sulfur atoms. Because of its color and luster, pyrite is also known as fool's gold.

Pyrite inclusions in quartz

An inclusion is a foreign matter contained in a host mineral. In this specimen, we can see pyrite inclusions seemingly floating in this clear quartz crystal. Inclusions strictly conform with natural law, and are never accidental. The crystals of pyrite in the quartz specimens below originally formed on the surfaces of quartz crystals. They were surrounded as the quartz crystals continued to grow. Scientists analyze inclusions, most of which are microscopic, for clues to a crystal's growth history. Their presence also helps identify a gemstone, and distinguish between natural and synthetic.

Pyrrhotite

Pyrrhotite is classified as a sulfide. All sulfides have sulfur, S, combined with a metal. Together with another class of sulfur-containing minerals, the sulfosalts, sulfides make up the majority of the important ore minerals.

Sperrylite

Sperrylite is classified as an arsenide. Arsenides all contain arsenic, As.

Stibnite

Sword-shaped crystals such as these were mined in Ehine, Japan in the late 1800's. Many were smelted to produce antimony, used to harden lead for munitions. The chemical composition of stibnite is Sb2S3.

Stibnite with barite

The black toothpick-shaped stibnite crystals formed first, out of a water solution containing antimony and sulfur. Next, the composition of the solution changed, causing barite crystals to grow on the top, looking like a dusting of snow.

Sylvanite