Goethite Archives - Cochise College Geology

Goethite

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Chemical Group: Oxide

Chemical Formula: Fe₂O₃.H₂O

Color: Yellowish brown, reddish brown, blackish brown

Streak: Brownish yellow to ocher yellow

Hardness: 5 to 5.5 Specific Gravity: 4.28

Tenacity: Brittle Fracture: Uneven

Cleavage: One direction, perfect

Crystal Forms: Orthorhombic system. Crystals are rare, but occur as striated prisms. Goethite is commonly fibrous, foliated, reniform, stalactitic, or concentric with radiating structure.

Mineral Associations: Commonly found with limonite

Uses: Iron ore, paint pigment

Occurrences: Lake Superior iron district and Colorado

Toxicity: When-swallowed: low When-inhaled: high

Additional Information: Goethite was named after a German poet and scientist. Goethite is a hydrous iron oxide. Its color ranges from a yellowish brown to a dark brown. Its streak is yellowish brown. The specimen shown below displays a radiating fibrous structure.

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Photos

Goethite 1 2 3 4 5 6 7 8 9 10

goethite-black botryoidal — Goethite-Black Botryoidal

goethite-black-stalactitic — Goethite-Black-Stalactitic

goethite-brown layer — Goethite-Brown Layer

goethite-brown radiating crystalline structures — Goethite-Brown Radiating Crystalline Structures

goethite-brown radiating crystals — Goethite-Brown Radiating Crystals

goethite-yellow brown radiating crystalline structure — Goethite-Yellow Brown Radiating Crystalline Structure

goethite-dark gray and brownlayers — Goethite-Dark Gray And Brownlayers

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