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inclusions. It may enclose or be enclosed by diamond. Bubbles of liquid CO2
are also found. Diamond also occurs as an inclusion in diamond. In
composition it is pure carbon. Diamond, graphite and charcoal are
allotrio-morphic forms of the same element carbon. Spontaneous
explosion of diamonds has been reported due perhaps to accumulated
strains. Phosphorescence is also common. It burns in air at 850°C. It
is insoluble in acids and alkalies. It becomes positively electrified
by friction and is a non-conductor of electricity. When exposed to
ultraviolet rays an electric current is produced through some diamonds.
After prolonged exposure to radium a colourless diamond becomes green.
Bort is a good conductor. It is also a good conductor of heat. It
feels colder to touch than glass and imitation stones and has a greasy
feel.
Fluorescence.—Under
ultraviolet rays, some colourless diamonds show a cornflower blue glow
and while greenish diamonds, show a greenish yellow glow. Diamond is
much more transparent to X-rays than other minerals and much more so
than glass imitations. The luminescence has been ascribed to the
inclusions of some unknown hydrocarbon minerals. Dake arrived at the
following conclusions: (1) non-fluorescent diamonds carried the least
amount of metallic inclusions and may be considered the purest form of
diamond, (2) the bort which fluoresced a strong blue contained the
greatest amount of metallic elements, and (3) diamonds which fluoresced
in different colours contain different proportions of various metallic
elements. The metallic elements found include chromium, iron, calcium,
aluminium and manganese. The more common metallic element was chromium.
In
recent years, the crystal structure and optical characters of diamond
have been studied intensively by Sir C. V.Raman and his co-workers at
the Indian Institute orScience, Bangalore. According to spectroscopic
studies
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