mineral

Pyrite (Fool's Gold)

Iron Disulfide (FeS2)

Hardness: 6-6.5 (Mohs scale), Color: Pale brass-yellow, Luster: Metallic, Crystal structure: Isometric (cubic, octahedral, pyritohedral), Cleavage: Poor/Indistinct, Specific gravity: 4.9–5.2

Hardness: 6-6

Identified March 20, 2026More mineral →

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Physical properties

Hardness: 6-6.5 (Mohs scale), Color: Pale brass-yellow, Luster: Metallic, Crystal structure: Isometric (cubic, octahedral, pyritohedral), Cleavage: Poor/Indistinct, Specific gravity: 4.9–5.2

Formation & geological history

Forms in diverse environments including magmatic segregation, hydrothermal veins, and sedimentary rocks under reducing conditions. It is the most common sulfide mineral and can be found in rocks from the Precambrian era to the present.

Uses & applications

Historically used as a source of sulfur and for making sulfuric acid; used in the manufacturing of lithium batteries and as a semiconductor. In jewelry, it is sold as 'marcasite' and is highly popular for decorative gemstone collections.

Geological facts

Commonly confused with gold due to its color, hence the nickname 'Fool's Gold.' Unlike gold, it is brittle and will shatter if struck. It creates sparks when struck against steel, which led to its name derived from the Greek word 'pyr' (fire).

Field identification & locations

Identify by its hardness (cannot be scratched by a penny), greenish-black streak (real gold has a yellow streak), and cubic crystal habit. Commonly found in Spain, Peru, Italy, and various locations across North America.