Yes, Black Diamonds are Carbonados – Carbonados have all the properties of the real diamonds but are dark grey- greenish black in color and are porous. The color of the Carbonados resembles charcoal, in fact the name ‘Carbonados’ means “burnt” in Portuguese. They were first discovered in Brazil around the 1840’s, though are supposed to be more than 2.6 to 3.8 billion years old. Carbonados have greater hardness than diamonds therefore were primarily used as abrasives and for cutting glass etc.
Origin – There is quiet a hullabaloo about how Carbonados came into being. The most common theory suggests that black diamond like regular white diamonds are also formed from carbon under high-pressure conditions in the bowels of the Earth. Shock metamorphism induced by meteoritic impact on the surface of the earth and radiations-induced by abrupt fission of uranium and thorium are a couple of other theories. Few others argue that Carbonados or Black diamonds have come from the outer space. They believe to have fallen as meteors on earth millions of years ago. Thus are found in alluvial, sedimentary deposits instead in the bowels of the earth and have unusual properties. Moreover the availability of Carabonados is limited to the alluvial deposits in the Central African Republic and in Brazil. To support this theory it has been lately discovered that the micro crystals in Carbonado have traces of nitrogen, hydrogen, and osbornite which are otherwise found only in meteors.
Unique Constitution – Carbonados or Blacks diamonds are very different from white diamonds- they are black and do not sparkle. Carbonados are polycrystalline, ploy means many and crystalline means crystals; which mean carbonados are made of multiple nano/micro crystals sticking together unlike a white diamond that is one single crystal. These micro-crystals have vacancies in them that make them porous. Moreover when the light falls on the diamond it gets absorbed or lost in these vacancies rather than being reflected back which is why they do not sparkle.
The Color– Black diamonds apart from being porous have heavy inclusions mostly graphite, pyrite or hematite that render the diamond opaque. These inclusions play an important role in determining the color intensity of the black diamonds. The color is also the result of the numerous cleavages or fractures that have become black due to graphitization. The color of the natural Black Diamond may range from grayish black to charcoal or dull gray depending on the inclusions. These not so perfectly black diamonds are heated or irradiated to improve the color. Natural-color black diamonds typically opaque and have a high luster that gives the stones a metallic appearance. However black diamonds are rare especially the naturally occurring black colored diamonds are very rare and are therefore very expensive.