Pyrite in Matrix

Physical Properties

Hardness: 6-6.5 on Mohs scale; Color: Pale brass-yellow to golden; Luster: Metallic; Crystal system: Isometric/Cubic; Cleavage: Poor/Indistinct; Specific Gravity: 4.9-5.2.

Formation & Geological History

Forms in diverse environments including hydrothermal veins, as an accessory mineral in igneous rocks, in contact metamorphic rocks, and in sedimentary rocks such as shale and coal. It forms at both high and low temperatures.

Uses & Applications

Historically used as a source of sulfur and sulfuric acid. Today, it is used in jewelry (often called 'marcasite' in trade), as a collector's specimen, and occasionally in the production of lithium-ion batteries.

Geological Facts

Often called 'Fool's Gold' because its color and high specific gravity can lead casual observers to mistake it for gold. However, pyrite is much harder and brittle, whereas gold is soft and malleable. It can create sparks when struck against steel.

Field Identification & Locations

Identify by its metallic luster, golden hue, and cubic crystal habits. Look for striations on crystal faces. Common in mining districts worldwide, notably Peru, Spain, and Italy. In the field, look for 'brass' specks in dark shale or quartz veins.

Identified on: 5/1/2026

Mode: Standard