mineral

Botryoidal Goethite on Quartz

Goethite (α-Fe3+O(OH)) on Quartz (SiO2)

Hardness: 5-5.5 (Goethite) / 7 (Quartz); Color: Black or dark brown (Goethite), clear to milky (Quartz); Luster: Submetallic to dull; Crystal structure: Orthorhombic (Goethite), Trigonal (Quartz); Specific Gravity: 3.3-4.3 (Goethite).

Hardness: 5-5
Color: Black or dark brown (Goethite), clear to milky (Quartz)
Luster: Submetallic to dull

Identified February 17, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the weathering of iron-rich minerals in oxidizing conditions or precipitation from hydrothermal fluids. Commonly found in gossan zones (weathered ore deposits) and sedimentary bog iron deposits. Formation ages vary by location, often spanning from Precambrian to Holocene.

Uses & applications

Goethite is a minor ore of iron. As a combined specimen with quartz, it is primarily used for mineral collecting, metaphysical displays, and occasionally in rough jewelry styles.

Geological facts

Goethite was named after the German polymath and writer Johann Wolfgang von Goethe. The 'botryoidal' texture seen on the black portion refers to a globular, grape-like external form which is a hallmark of this iron oxide mineral.

Field identification & locations

Identify in the field by the distinct grape-like (botryoidal) or radiating crystal habit and a yellow-brown streak. It is commonly found in iron mines and limestone caverns throughout the world, notably in Morocco, Germany, and the USA (Minnesota/Michigan).

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