Transmitted Off Crossed Polarized Light Illumination
Carborundum is a man-made abrasive. Its presence in a sample indicates the use of abrasives and not the
presence of natural minerals. It is often a low level impurity in abrasive products containing primarily
garnet, or corundum (emery). When it is found with these minerals it suggests that these two natural minerals
are present not as natural background but rather as an abrasive assemblage. Carborundum, also known as
silicon carbide, at trace levels indicates that the presence of abrasive assemblages should be investigated
in the sample. Silicon carbide has an irregular series of interference colors. The combination of these
irregular colors, very high refractive indices, and sharply angular shape is used to suggest its presence.