Bixbyite is a rare manganese iron oxide characterized by its distinctive metallic black, cubic crystals. It is most famous among collectors for the sharp, well-formed cubes found in the rhyolite cavities of the Thomas Range in Utah, often associated with topaz.
Is this bixbyite-(mn)?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch bixbyite-(mn) with a known reference. Bixbyite-(Mn) sits at Mohs 6-6.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Bixbyite-(Mn) leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Bixbyite-(Mn) typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: cubic. Typical habit: cubo-octahedral crystals, often showing striated faces.
Often confused with
Bixbyite-(Mn) vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Bixbyite-(Mn) leaves black, Iron Ore leaves reddish-brown to black; luster reads metallic on Bixbyite-(Mn) and metallic to submetallic on Iron Ore.
How to tell apart: Streak differs — Bixbyite-(Mn) leaves black, Hausmannite leaves brownish-red; luster reads metallic on Bixbyite-(Mn) and submetallic on Hausmannite.
Often found alongside bixbyite-(mn)
Minerals reported to co-occur with bixbyite-(mn). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Mn³⁺,Fe³⁺)₂O₃
- Mohs hardness
- 6-6.5
- Density
- 4.9-5.0 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Cubo-octahedral Crystals, Often Showing Striated Faces
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Mineral Specimen
- Host rock
- Rhyolite Cavities, Hydrothermal Veins
- Typical price
- $50-500 depending on crystal size and quality
Where rockhounds find bixbyite-(mn)
Classic worldwide localities
- Thomas Range, Utah, USA
- Artigas, Uruguay
- Kalahari Manganese Field, South Africa
- Pachapaqui, Peru
Field-hunting tip
Look in rhyolite cavities, hydrothermal veins country — that is the host setting where bixbyite-(mn) typically forms. If you start seeing topaz, beryl, spessartine in float, you are in the right ground. Field specimens usually show a cubo-octahedral crystals, often showing striated faces habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify bixbyite-(mn)?+
Where is bixbyite-(mn) found?+
How much is bixbyite-(mn) worth?+
What rocks look like bixbyite-(mn)?+
What minerals are found with bixbyite-(mn)?+
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Find bixbyite-(mn) on the map
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