Bixbyite is a distinct manganese iron oxide that typically forms as brilliant, metallic black cubo-octahedral crystals. It is most famous to collectors for the exceptional specimens found in the rhyolite cavities of the Thomas Range in Utah. It is highly valued for its sharp crystal faces and high luster.
Is this bixbyite?
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 with a known reference. Bixbyite 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. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: cubic. Typical habit: crystalline, massive.
Often confused with
Bixbyite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside bixbyite
Minerals reported to co-occur with bixbyite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Mn,Fe)₂O₃
- Mohs hardness
- 6-6.5
- Density
- 4.945 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Crystalline, massive
- Cleavage
- {111}, in traces
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In lithophysal cavities in rhyolite; in metamorphosed manganese ores
Where rockhounds find bixbyite
1 mapped spotsClassic worldwide localities
- Thomas Range, Juab Co., Utah, USA
- A number of places in the Black Range, Sierra and Catron Cos., New Mexico, USA
- Saddle Mountain, Pinal Co., Arizona, USA
- Cerro de Mercado, Durango, Mexico
- Barranca del Cobre, Chihuahua, Mexico
- Tepetate, San Luis Potosi, Mexico
Field-hunting tip
Where it forms: In lithophysal cavities in rhyolite; in metamorphosed manganese ores. If you start seeing topaz, spessartine, beryl in float, you are in the right ground. Typical habit: crystalline, massive. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah. Start trip planning there.
Common questions
How do you identify bixbyite?+
Where is bixbyite found?+
Can I find bixbyite in the United States?+
What rocks look like bixbyite?+
What minerals are found with bixbyite?+
What kind of rock does bixbyite form in?+
What is bixbyite used for?+
Find bixbyite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
