This page contains a Flash digital edition of a book.
course there is black glass. Anu says: “These diamonds may not


always be truly ‘black’ when closely examined under magnification and high intensity lighting. They often include a mixture of shades of grey, brown, green, blue or violet. The black colour appearance is created by a high concentration of dark inclusions, which create a general translucency or opacity. Diamonds that contain a dark shade of brown, green, blue, violet or olive-type colour can also appear black under every day lighting.” There are various different


types of natural black diamonds. The colour can be due to a high


concentration of tiny, dark particles throughout all or the majority


42 | Jewellery Focus





THERE ARE VARIOUS DIFFERENT TYPES OF


NATURAL BLACK DIAMONDS. THE COLOUR CAN BE DUE TO A HIGH CONCENTRATION OF TINY, DARK PARTICLES THROUGHOUT ALL OR THE MAJORITY OF THE STONE


of the stone. This will make the overall appearance a neutral grey to deep black depending upon the concentration. Alternatively the black appearance may be caused by a high concentration of dark foreign material and dark internal cleavage and micro-fissures. Not all diamonds are single crystals.


Some may be a concentration of numerous tiny diamond crystals. This form of diamond, known as Polycrystalline Bort, is commonly used


for industrial purposes and is now being faceted for use in jewellery as it is naturally truly black and opaque. Another unique polycrystalline variety is carbanado. Due to its polycrystalline structure carbanado is very hard to polish and is the toughest form of diamond. The colour can range from gunmetal grey, to black, to dark brown. Treated black diamonds enhanced


by irradiation have been on the market since the 1950s. These


jewelleryfocus.co.uk | November 2013





Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52