mineral

Bixbyite on Rhyolite

Bixbyite (Mn2+,Fe3+)2O3

Hardness: 6.0-6.5; Color: Metallic black to steel grey; Luster: Metallic; Crystal Structure: Isometric (cubic/octahedral habit); Cleavage: None/Irregular; Specific Gravity: 4.9-5.0

Hardness: 6
Color: Metallic black to steel grey
Luster: Metallic

Identified May 8, 2026More mineral →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 6.0-6.5; Color: Metallic black to steel grey; Luster: Metallic; Crystal Structure: Isometric (cubic/octahedral habit); Cleavage: None/Irregular; Specific Gravity: 4.9-5.0

Formation & geological history

Formed in gas cavities (vugs) within pneumatolytic rhyolite lavas where high-temperature manganese-rich vapors crystallize during the cooling of volcanic rocks.

Uses & applications

Predominantly valued as a rare collector's mineral specimen due to its distinct geometric crystal form; manganese is used in steel production, but this source is too rare for industrial mining.

Geological facts

Bixbyite was named after Maynard Bixby, who discovered the first specimens in Utah's Thomas Range. It is often found associated with red beryl and topaz in volcanic host rocks.

Field identification & locations

Identify by its distinct cubic or modified octahedral metallic black crystals sitting within the vugs of a pinkish, porous rhyolite matrix. Common locations include the Thomas Range and Wah Wah Mountains in Utah, USA.