Although most black diamonds on the market today are either superheated or irradiated to an almost black color, natural black diamonds do exist, though they are extremely rare. The 67.5 carat “Black Orlov” is perhaps the most celebrated natural black diamond. Whether color treated or natural, however, what defines a diamond is its chemical composition (carbon with minor impurities) and its crystalline atomic structure. That is, the entire diamond can be defined as growing from a cubic or isometric crystal structure.

Carbonado is a curious mineral that is often referred to as “black diamond” but is more accurately described as a polycrystalline or aggregate material of amorphous carbon, graphite, and diamond.

This aggregate material has a greater hardness than diamond and is used primarily in industry.  Carbonado resembles charcoal, and its name means “burned” in Portuguese, but what burned it may be truly extraordinary.

Carbonado might have an extraterrestrial origin, which could account for some of its unusual properties. Unlike diamonds, carbonados are never found in igneous kimberlite rock formed deep within the earth but in alluvial, sedimentary deposits instead. The micro-diamonds present in carbonado (typically smaller than 20 microns or 20 millionths of a meter) lack traces…