Oxycalciomicrolite is a rare member of the pyrochlore supergroup, typically appearing as small, sharp octahedral crystals in complex granite pegmatites. It is often found associated with other rare-element minerals and is prized primarily by advanced mineral collectors for its complex chemistry and distinct crystal form.
Is this oxycalciomicrolite?
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 oxycalciomicrolite with a known reference. Oxycalciomicrolite sits at Mohs 5-5.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to resinous.
- 4Match the color rangeCompare against the expected color range: brownish yellow, brownish red.
- 5Look at form & habitCrystal system: cubic. Typical habit: octahedral crystals.
Often confused with
Oxycalciomicrolite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside oxycalciomicrolite
Minerals reported to co-occur with oxycalciomicrolite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂Ta₂O₇
- Mohs hardness
- 5-5.5
- Density
- 6.333 g/cm³
- Streak
- White
- Luster
- Vitreous to resinous
- Transparency
- Translucent to transparent
- Crystal system
- Cubic
- Crystal habit
- Octahedral crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- In the saprolite of a weathered granitic pegmatite
Where rockhounds find oxycalciomicrolite
Classic worldwide localities
- Fumal pegmatite, 18 km north of Nazareno, Minas Gerais, Brazil (type locality), Italy
- Varuträsk pegmatite, northeastern Sweden, Italy
- Pegmatites of the Vigezzo Valley, western Alps, Italy
Field-hunting tip
Where it forms: In the saprolite of a weathered granitic pegmatite. If you start seeing columbite subgroup minerals, cassiterite, hematite in float, you are in the right ground. Typical habit: octahedral crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify oxycalciomicrolite?+
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What rocks look like oxycalciomicrolite?+
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Find oxycalciomicrolite on the map
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