Part of: The history of diamonds
A rough diamond is a diamond as it comes out of the ground, before it has been cut and polished. Rough diamonds grow as crystals of pure carbon, most often in eight-sided octahedral shapes, with a frosted or waxy surface rather than the sparkle of a cut stone. Most rough is cut into polished gems, but uncut and lightly polished rough diamonds are also set in jewellery for their natural look. "A rough diamond" is also a British phrase for someone kind-hearted with rough manners.
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What does a rough diamond look like?
Diamond crystallises from carbon deep in the Earth under great heat and pressure. As a crystal it grows in regular shapes, but rough diamonds are often rounded, etched or broken by their journey to the surface. Their surface usually looks frosted, greasy or waxy, and small triangular pits called trigons are common on octahedral faces.
- Octahedron
- What it looks like
- Two pyramids joined at the base, eight triangular faces; the most common form
- Dodecahedron
- What it looks like
- A rounded, twelve-faced crystal
- Cube
- What it looks like
- A cube shape, often with a rougher surface
- Macle
- What it looks like
- A flat, triangular twinned crystal
From rough to polished
- Sorting. Rough diamonds are sorted by size, shape, quality and colour.
- Planning. The cutter studies each crystal to decide how to get the best polished stone from it.
- Cutting and polishing. The rough is sawn or cleaved, shaped and faceted. Much of the original crystal is lost in cutting.
Where rough diamonds come from
Diamonds are mined in Africa (Botswana, South Africa, Namibia, Angola and the Democratic Republic of Congo), in Russia, Canada and Australia, and from historic sources in India and Brazil. Since 2003 international trade in rough diamonds has been governed by the Kimberley Process Certification Scheme, set up to keep conflict diamonds out of the market.
Rough diamonds in jewellery
Uncut and partly polished diamonds have been set in jewellery for centuries; early Indian and European jewels often used natural crystals or simply polished stones. Today designers set rough diamonds for their organic look, sometimes alongside brilliant-cut stones, as in the Cartier ring in our photograph.
How to tell a rough diamond from an imitation
0 of 4 checked
1The surface
A frosted or waxy skin with natural growth marks, not glassy smooth faces.
2The shape
Crystal forms such as octahedra, often with rounded edges.
3The hardness
Diamond is the hardest natural material; quartz and glass imitations show wear and scratches.
4Testing
A jeweller can confirm diamond with a thermal or electrical tester.
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What decides the value of diamond jewellery?
For diamonds: the size, colour, clarity and, for polished stones, the cut; any laboratory certificate; then the maker, the metal and the condition of the piece. Rough diamonds are judged on size, colour, clarity and shape. We never publish figures; every piece is different.
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Questions people ask
What is a rough diamond?
A diamond in its natural, uncut state, as it is mined, before cutting and polishing.
Are rough diamonds real diamonds?
Yes. They are natural diamonds that have not yet been cut and polished.
What does a rough diamond look like?
Usually a frosted or waxy crystal, often an eight-sided octahedron, with rounded edges and small triangular pits on its faces.
What does "a rough diamond" mean?
In British English it describes a person who is kind or good-hearted but lacks polish or refined manners. "A diamond in the rough" means the same.
What is the Kimberley Process?
An international certification scheme, in force since 2003, that governs the trade in rough diamonds to keep conflict diamonds out of the market.
Can rough diamonds be set in jewellery?
Yes. Uncut and partly polished diamonds are set in rings, pendants and earrings, sometimes alongside brilliant-cut stones.
Related guides
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