Black diamonds, or carbonado, are a rare, tough, and opaque polycrystalline form of diamond characterized by a porous, black, or dark grey appearance. Unlike gem-quality single crystals, they are composed of many small, tightly bonded diamond crystallites, making them exceptionally hard and resistant to fracturing.
Is this black diamond?
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 black diamond with a known reference. Black Diamond sits at Mohs 10 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Black Diamond leaves a none streak.
- 3Read the lusterHold the specimen under a strong light. Black Diamond typically shows a adamantine luster.
- 4Match the color rangeCompare against the expected color range: black, dark gray.
- 5Look at form & habitCrystal system: cubic. Typical habit: massive, polycrystalline aggregates.
Often confused with
Black Diamond vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Black Diamond is noticeably harder (Mohs 10 vs. 5-6.5); streak differs — Black Diamond leaves none, Iron Ore leaves reddish-brown to black; luster reads adamantine on Black Diamond and metallic to submetallic on Iron Ore.
How to tell apart: Black Diamond is noticeably harder (Mohs 10 vs. 5.5-6.5); streak differs — Black Diamond leaves none, Magnetite leaves black; luster reads adamantine on Black Diamond and metallic on Magnetite.
How to tell apart: Black Diamond is noticeably harder (Mohs 10 vs. 1-2); streak differs — Black Diamond leaves none, Graphite leaves black; luster reads adamantine on Black Diamond and metallic on Graphite.
Often found alongside black diamond
Minerals reported to co-occur with black diamond. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- C
- Mohs hardness
- 10
- Density
- 3.1-3.4 g/cm³
- Streak
- None
- Luster
- Adamantine
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Massive, Polycrystalline Aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Gemstone, Industrial, Collector
- Host rock
- Alluvial Deposits
- Typical price
- $50-500 per carat depending on quality
Where rockhounds find black diamond
1 mapped spotsClassic worldwide localities
- Brazil
- Central African Republic
- Democratic Republic of the Congo
Field-hunting tip
Look in alluvial deposits country — that is the host setting where black diamond typically forms. If you start seeing quartz, feldspar, diamond in float, you are in the right ground. Field specimens usually show a massive, polycrystalline aggregates habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Texas — start trip planning there.
Common questions
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Find black diamond on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
