INHERENT QUALITIES 113
causes,
are found to be doubly refractive. This means that a ray of light on
entering the stone is split and refracted at two different angles.
What
might be termed the reenforcement of the diamond's brilliancy is its
hardness. It is brilliant because it is hard, and it remains brilliant
for the same reason. Other stones by the wear and tear of contact
become scratched, and their corners are roughened, but the diamond,
year after year and generation after generation, remains undimmed. The
hardest of all things, wearing does not mar its smooth facets and sharp
corners. It laughs at the rough hand of time. Some years ago a German
mineralogist named Moh arranged a scale, since known as Moh's scale,
giving the relative hardness of various minerals, from talc, the
softest, to diamond, the hardest. He made ten divisions as follows:
