Usturite is a rare calcium antimony zirconium oxide, typically light brown or yellow. It was approved as a distinct mineral species in 2009. It was first described from Within the Upper Chegem caldera, Northern Caucasus, Kabardino-Balkaria, Russia.
Is this usturite?
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 usturite with a known reference. Usturite sits at Mohs 5-6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white with yellow tint.
- 3Read the lusterHold the specimen under a strong light. Luster: strong vitreous.
- 4Match the color rangeCompare against the expected color range: yellow.
- 5Look at form & habitCrystal system: cubic. Typical habit: bipyramidal crystals.
Often confused with
Usturite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Zircon is the harder of the two (Mohs 7.5 vs. 5-6); luster reads strong vitreous on Usturite and vitreous to adamantine; greasy when metamict on Zircon.
How to tell apart: Streak differs, so Usturite leaves white with yellow tint, Pyrochlore leaves brown; luster reads strong vitreous on Usturite and vitreous to resinous on Pyrochlore.
How to tell apart: Streak differs, so Usturite leaves white with yellow tint, Euxenite-(Y) leaves yellowish, grayish, or reddish brown; luster reads strong vitreous on Usturite and brilliant submetallic, waxy to resinous on fractures on Euxenite-(Y).
Often found alongside usturite
Minerals reported to co-occur with usturite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₃(SbZr)(FeO₄)₃
- Mohs hardness
- 5-6
- Density
- 4.470 g/cm³
- Colors
- Streak
- White with yellow tint
- Luster
- Strong vitreous
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Bipyramidal crystals
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In the cuspidine zone of high-temperature skarns in a carbonate-silicate xenolith at the contact with ignimbrites
Where rockhounds find usturite
Classic worldwide localities
- Within the Upper Chegem caldera, Northern Caucasus, Kabardino-Balkaria, Russia
Field-hunting tip
Where it forms: In the cuspidine zone of high-temperature skarns in a carbonate-silicate xenolith at the contact with ignimbrites. If you start seeing cuspidine, larnite, wadalite in float, you are in the right ground. Typical habit: bipyramidal crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify usturite?+
Where is usturite found?+
Is usturite safe to handle?+
What rocks look like usturite?+
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Find usturite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
