Diamond rough crystal

Rough diamond crystal: pure carbon formed under high pressure and temperature in Earth's mantle, mined in Africa, Russia, and Brazil.

About this subject

Rough diamond is a crystalline form of carbon, the hardest known natural material. It forms between 140 and 190 kilometers deep in Earth's mantle, under temperatures exceeding 900°C and extreme pressures, over billions of years. These crystals are brought to the surface by kimberlite volcanic eruptions, creating kimberlite pipes that are the primary commercial sources of diamonds. Major producers include Botswana, Russia, Canada, and South Africa, while Brazil has historical deposits in Minas Gerais, Mato Grosso, and Bahia, notably the carbonado type found in the Chapada Diamantina region. Rough diamonds exhibit a range of colors, from colorless (most valued for gems) to yellow, brown, and rare blue, green, or pink hues, caused by impurities such as nitrogen or boron. Besides jewelry, about 70% of mined diamonds are used industrially, exploiting their extreme hardness and thermal conductivity for cutting tools, abrasives, and heat sinks in electronics. Brazil, though not a top current producer, played a historic role: in the 18th century, diamond discoveries in Minas Gerais fueled the gold rush and colonial expansion, and artisanal mining still extracts crystals from rivers and alluvial beds today.

Frequently Asked Questions

How to tell if a rough diamond is real?

Rough diamonds have a greasy luster, high density (3.5 g/cm³), and conduct heat quickly. Home tests include checking if it scratches glass or does not fog with breath. Definitive testing uses thermal conductivity or a gemologist.

What is the difference between rough and cut diamonds?

A rough diamond is the natural crystal as mined, uncut. A cut diamond is shaped and polished to enhance brilliance and fire, used in jewelry.

Where are diamonds found in Brazil?

Main areas are Minas Gerais (Diamantina, Patos), Mato Grosso (Juína, Alto Paraguai), and Bahia (Lençóis, Mucugê). Extraction occurs in riverbeds (alluvial) and kimberlite pipes.