Breyite is a rare high-pressure polymorph of calcium silicate found as inclusions within diamonds originating from the Earth's lower mantle. Because it only forms under extreme deep-earth conditions, it is almost exclusively identified through microscopic analysis of diamond-hosted grains.
Is this breyite?
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 breyite with a known reference. Breyite sits at Mohs 7-7.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Breyite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Breyite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: microscopic inclusions.
Often confused with
Breyite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside breyite
Minerals reported to co-occur with breyite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaSiO₃
- Mohs hardness
- 7-7.5
- Density
- 3.37 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Tetragonal
- Crystal habit
- Microscopic Inclusions
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Scientific Research
- Host rock
- Lower Mantle Xenoliths
- Typical price
- n/a (research specimens only)
Where rockhounds find breyite
Classic worldwide localities
- Brazil
- South Africa
- Russia
Field-hunting tip
Look in lower mantle xenoliths country — that is the host setting where breyite typically forms. If you start seeing diamond, olivine, enstatite in float, you are in the right ground. Field specimens usually show a microscopic inclusions habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find breyite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
