Diamond rough crystal

Rough diamond is the natural form of the hardest mineral on Earth, formed under high pressure and temperature in the Earth's mantle.

About this subject

Rough diamonds, also called raw diamonds, are natural carbon crystals formed deep within the Earth's mantle, about 150 to 200 kilometers below the surface. Their creation requires extreme pressures (over 4.5 GPa) and temperatures (900 to 1300 °C) over billions of years. These gemstones are brought to the surface through kimberlite volcanic eruptions, forming kimberlite pipes that are the primary sources of diamonds.

While best known as faceted gemstones in jewelry, rough diamonds have numerous industrial applications due to their exceptional hardness (10 on the Mohs scale) and high thermal conductivity. They are used in cutting tools, polishing abrasives, and high-performance electronic components. The cubic crystal structure of diamond gives it these unique properties, setting it apart from other materials.

Diamond mining has significant economic impact in countries such as Russia, Botswana, Canada, and Brazil. In Brazil, the first discoveries occurred in the 18th century in Minas Gerais, fueling the gold and diamond cycle. Famous diamonds like the Cullinan (discovered in South Africa) and the Koh-i-Noor began as rough crystals that were cut over centuries. The evaluation of a rough diamond considers weight, purity, color, and crystal shape, with clarity being a key factor for gemological value.

Frequently Asked Questions

How is a rough diamond formed?

Rough diamonds form in the Earth's mantle, at depths of 150 to 200 km, under pressures above 4.5 GPa and temperatures between 900 and 1300 °C. Pure carbon crystallizes into a cubic structure over billions of years, and is brought to the surface by kimberlite volcanic eruptions.

What is the difference between rough and cut diamonds?

Rough diamonds are natural crystals extracted from mines, without polishing or faceting. Cut diamonds have undergone a cutting process that enhances their brilliance and fire, removing impurities and creating facets to reflect light.

Where are rough diamonds found?

Rough diamonds are mainly found in kimberlite pipes and alluvial deposits. The largest producers are Russia, Botswana, Canada, Angola, and Brazil. In Brazil, occurrences are in Minas Gerais, Mato Grosso, and Bahia.