Diamond rough crystal

The rough diamond, a pure carbon crystal, is the hardest natural material, formed kilometers deep within the Earth.

About this subject

A rough diamond is a crystal of carbon crystallized in the cubic system, known for its exceptional hardness (10 on the Mohs scale). Its formation occurs in the Earth's mantle, at depths between 140 and 190 kilometers, under temperatures above 1000°C and extreme pressure. Diamonds are brought to the surface by kimberlitic volcanic eruptions, forming kimberlite pipes, the primary sources. Secondary deposits occur in riverbeds and coastlines, where crystals were transported by erosion.

Major producing countries include Russia, Botswana, Canada, Angola, and South Africa. Rough diamonds are classified by color, clarity, size, and shape. Most natural diamonds have internal imperfections (inclusions) and color variations, from colorless to yellow, brown, blue, green, and pink. The famous Hope Diamond, for example, is a rare blue diamond.

Economically, rough diamonds are evaluated before cutting. Cutting and polishing transform the rough crystal into brilliant gems, but about 80% of mined diamonds are used industrially, in cutting, drilling, and polishing tools due to their hardness. The discovery of synthetic diamonds in the 20th century revolutionized the market, but natural ones still hold high value as gemstones.

Culturally, diamonds symbolize love and status, popularized by campaigns like 'Diamonds are forever'. In Brazil, diamond mining occurs mainly in Minas Gerais and Bahia, with highlights like the 'Star of the South' diamond, weighing 254 carats.

Frequently Asked Questions

How are rough diamonds formed?

Diamonds form in the Earth's mantle, at depths of 140 to 190 km, under temperatures above 1000°C and very high pressure. Carbon crystallizes into the diamond cubic structure. They are brought to the surface by kimberlitic volcanic eruptions.

What is the difference between a rough diamond and a cut diamond?

A rough diamond is the natural crystal extracted from the mine, without any cutting or polishing. A cut diamond has undergone a cutting and polishing process to maximize its brilliance and fire, turning it into a gemstone ready for jewelry.

Where are the world's largest rough diamonds found?

The largest rough diamonds ever found come from mines in South Africa (Cullinan, 3106 carats), Botswana (Lesedi La Rona, 1109 carats), and Canada (Diavik Foxfire, 187 carats). Russia also has large deposits.