Goethite generally forms through the weathering of iron-rich mineral deposits. It is a common mineral, often a dark, nondiscript mineral, though specimens from a few localities are quite the opposite, hosting delicate and aesthetic crystal growths. Typically black, it can also be brown, yellow-brown, red-brown, yellow and occasionally iridescent with a submetallic, silky or dull luster. It also serves as a matrix for other aesthetic minerals, particularly Vanadinite, and is associated with numerous other minerals including Quartz, Calcite, Barite, Malachite and Pyrite.
The crystal system for Goethite is orthorhombic, often in velvety radial aggregates of acicular crystals, botryoidal growths and acicular crystal sprays within Geodes and on druzy Quartz. Other forms include stalactitic, massive, encrustation, bladed and pseudomorph.
Localities for Goethite are widespread. Notable locations include Australia, England, Germany, Morocco and the USA (Arizona, Colorado, Michigan).
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