It's an unusual species of diamond, called a "carbonado

carbonado

Carbonado, commonly known as black diamond, is one of the toughest forms of natural diamond. It is an impure, high-density, micro-porous form of polycrystalline diamond consisting of diamond, graphite, and amorphous carbon, with minor crystalline precipitates filling pores and occasional reduced metal inclusions.

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." And at around the size of a lemon, it's a huge carbonado. Like all diamonds, carbonados are made of carbon atoms that, under conditions of immense heat and pressure, form into an exquisite crystal structure.

How much is a space diamond worth?

A Billion-Year-Old Space Diamond Just Sold for $4.3 Million in Crypto. A magnifying glass.

What is the space diamond called?

Black diamonds, also known as Carbonado diamonds, can be dated to between 2.6 to 3.8 billion years ago and have trace amounts of nitrogen and hydrogen -- elements found in interstellar space. They also contain osbornite, a mineral present in meteorites.