mineral

Pyrite (on Shale/Matrix)

Iron Disulfide (FeS2)

Hardness: 6-6.5 Mohs scale; Color: Brass-yellow (often called Fool's Gold); Luster: Metallic; Crystal structure: Isometric (often cubic or pyritohedral); Cleavage: Poor/indistinct; Specific Gravity: 4.9-5.2.

Hardness: 6-6
Color: Brass-yellow (often called Fool's Gold)
Luster: Metallic

Identified March 24, 2026More mineral →

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Physical properties

Formation & geological history

Formed through hydrothermal veins, as an accessory mineral in igneous rocks, or through sedimentary processes in oxygen-deficient environments (reducing conditions). This specimen appears to be a fine-grained sedimentary host containing microscopic to small metallic crystals.

Uses & applications

A primary source of sulfur and sulfuric acid in the past; occasionally used in jewelry (as 'marcasite'); most common as a mineral specimen for collectors and educational purposes.

Geological facts

Known as 'Fool's Gold' due to its resemblance to real gold, though it is much harder and more brittle. It can actually contain trace amounts of real gold within its structure in certain geological deposits.

Field identification & locations

Identify in the field by its brassy color, high density, and brittle nature (it will crush to a black powder under pressure, whereas gold is malleable). This specimen shows a metallic sheen on a dark, fine-grained host rock likely found in tailing piles or creek beds.