Diamond rough crystal

Rough diamond crystals, like the one in the image, are natural forms of crystallized carbon with a cubic structure, mined from kimberlites in regions such as Africa and Brazil.

About this subject

Rough diamonds are fragments of pure carbon subjected to extreme pressure and temperature in the Earth's mantle, between 150 and 200 kilometers deep. Their cubic crystalline structure, with tetrahedrally bonded atoms, gives them maximum hardness (10 on the Mohs scale). The yellowish or brownish color common in rough crystals is due to nitrogen inclusions; colorless diamonds are rarer. Primary deposits are found in kimberlite volcanic pipes, such as the Cullinan mine in South Africa, or in alluvial deposits, like the rivers of Diamantina, Minas Gerais, Brazil. Brazil was the world's largest producer until the 18th century, following the discovery of diamonds in 1725 in Diamantina. Rough crystals are cut and polished to enhance their brilliance and fire, but non-gem-quality industrial diamonds are used in cutting tools, abrasives, and heat sinks due to their exceptional thermal conductivity. Synthetic diamonds, created by CVD or high pressure, compete with natural ones in industrial applications. One of the largest rough diamonds ever found is the Cullinan, at 3,106 carats, discovered in 1905.

Frequently Asked Questions

What determines the value of a rough diamond?

The value depends on the 4 Cs: carat (weight), color, clarity (inclusions), and cut (potential brilliance). Rough diamonds with fewer inclusions and near-colorless color are more valuable as gems.

Where are rough diamonds found in Brazil?

Major deposits are in Minas Gerais (Diamantina, Grão Mogol), Mato Grosso (Juína, Chapada dos Guimarães), and Bahia (Lençóis). Brazil also has alluvial diamonds in riverbeds.

What is the difference between rough and cut diamond?

A rough diamond is extracted from nature without alteration. Cutting and polishing transform it into a faceted gem to maximize brilliance and fire.