San Diego Natural History Museum--Your Nature ConnectionSDNHM Field Guide
[Pyrite. Collection of the San Diego Natural History Museum.]

Pyrite

From the Greek word, pyr, meaning "fire."

Description and Occurrence

Pyrite crystal usually forms as a cube with fine ridges (striations) on the crystal's faces. Less commonly, it forms as octahedrons (eight-sided shapes), nodules, or massive forms. It can also occur as coarse granules.

Pyrite is called fool's gold because its brassy yellow color is very similar to gold. Although it looks like gold, its other physical properties are very different. Pyrite is harder, less dense, and more brittle. It leaves a greenish-black streak while gold leaves a golden-yellow one. However, pyrite is often associated with the presence of gold and copper, and locating fool's gold may mean the real thing isn't far off.

Pyrite is the most common of the sulfide minerals and can be found worldwide. It's the most important source of sulfur after native sulfur.

Field Notes: The mineral has a brassy yellow color. It tends to form in cubes. The crystal faces are striated (lined with fine ridges). Striking it with steel produces a spark.


Physical Properties

Color Streak Transparency Luster Hardness Cleavage Fracture Specific gravity Crystal form
pale yellow to brass yellow greenish black opaque metallic 6 to 6.5 imperfect conchoidal, brittle 4.9 to 5.2 isometric

Photo: Pyrite. Collection of the San Diego Natural History Museum
Photo credit: Linda West

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