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.

Hardness

7-7.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareGarnet Group family

Breyite

Hardness: 7-7.5
Luster: Vitreous
Streak: White
Transparency: Transparent

No image

Is this breyite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try 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.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Breyite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Breyite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: colorless, white.
5
Look at form & habit
Crystal system: tetragonal. Typical habit: microscopic inclusions.

Often confused with

Breyite vs. its common look-alikes, and how to tell them apart in the field.

mineral

Wollastonite

Mohs 4.5-5

How to tell apart: Breyite is noticeably harder (Mohs 7-7.5 vs. 4.5-5).

How to tell apart: Breyite is noticeably harder (Mohs 7-7.5 vs. 6).

Compare →

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
Colors: Colorless White
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, 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

How do you identify breyite?+

Mohs hardness is 7-7.5. It typically shows a vitreous luster. The streak is white. Common colors include colorless, white.

Where is breyite found?+

Notable localities include Brazil; South Africa; Russia.

How much is breyite worth?+

Typical asking prices fall in the range of n/a (research specimens only). Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like breyite?+

Breyite is most often confused with Wollastonite, Larnite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with breyite?+

Breyite commonly co-occurs with Diamond, Olivine, Enstatite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does breyite form in?+

Breyite typically forms in lower mantle xenoliths. Working float back to the host body is the standard way to chase a fresh occurrence.

What is breyite used for?+

Breyite is used in collector, scientific research.

Find breyite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.