mineral

Brown botryoidal mineral specimen, likely goethite/limonite

Goethite (α-FeO(OH)), possibly mixed with limonite (hydrated iron oxides)

AI-generated identification · may be incorrect

Dark brown to nearly black, earthy-to-submetallic luster with rounded botryoidal surfaces; hardness about 5–5.5 for goethite, specific gravity roughly 3.3–4.3. Crystal structure is orthorhombic, though specimens commonly appear massive or botryoidal.

Identified September 16, 2026More mineral →

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Physical properties

Formation & geological history

Forms by oxidation and weathering of iron-bearing minerals, commonly in iron-rich hydrothermal veins, caves, soils, and gossans. Formation age depends on the deposit and may range from ancient to recent weathering.

Uses & applications

Used as an iron ore and historically as a brown/yellow pigment; attractive botryoidal pieces are collected but are generally inexpensive.

Geological facts

Goethite commonly produces yellow-brown streak and may occur with hematite, quartz, or manganese oxides. The image’s low resolution prevents secure separation from hematite or other dark iron-oxide minerals.

Field identification & locations

Field identification: test streak on unglazed porcelain—goethite/limonite gives yellow-brown, while hematite gives red-brown; it is also relatively heavy and nonmetallic. Common worldwide, especially in oxidized ore deposits and lateritic soils.