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?
4-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.
- 2Read the lusterHold the specimen under a strong light. Luster: adamantine.
- 3Match the color rangeCompare against the expected color range: black, dark gray.
- 4Look 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); luster reads adamantine on Black Diamond and metallic or submetallic to dull on Hematite.
How to tell apart: Black Diamond is noticeably harder (Mohs 10 vs. 5.5-6.5); luster reads adamantine on Black Diamond and metallic to submetallic, may be dull on Magnetite.
How to tell apart: Black Diamond is noticeably harder (Mohs 10 vs. 1-2); luster reads adamantine on Black Diamond and metallic; may be dull, earthy 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
- Luster
- Adamantine
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Massive, polycrystalline aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Gemstone, Industrial, Collector
- Host rock
- alluvial deposits
Where rockhounds find black diamond
1 mapped spotsClassic worldwide localities
- Brazil
- Central African Republic
- Democratic Republic of the Congo
Field-hunting tip
Where it forms: alluvial deposits. If you start seeing quartz, feldspar, diamond in float, you are in the right ground. Typical habit: massive, polycrystalline aggregates. 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
How do you identify black diamond?+
Where is black diamond found?+
Can I find black diamond in the United States?+
What rocks look like black diamond?+
What minerals are found with black diamond?+
What kind of rock does black diamond form in?+
What is black diamond used for?+
Find black diamond on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
