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PRECIOUS STONES.
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In
value an Emerald of best quality ranks nearly as high as the Ruby, a
perfect stone of one carat often selling for £20; owing to the
difficulty of obtaining Emeralds without imperfections in the larger
sizes, the value of flawless stones increases very rapidly with size.
Besides the frequently occurring flaws Emeralds often show inclusions,
rendering the stone " mossy." The colour too may be irregularly
distributed; sometimes only the extremity of a crystal is transparent.
A fissured stone only increases in value in proportion to its size, and
it may be worth about £2 10s. per carat. The other varieties of
Beryl are often found in considerable quantity and in large pieces,
hence the value is much lower and varies very closely with the weight.
There
are numerous famous specimens of Emerald ; two well known ones may be
instanced: the Czar's Emerald, which measures ten inches in length and
five in diameter, and the Emerald belonging to the Duke of Devonshire,
which weighs 1,350 carats, and is an almost perfect specimen.
Owing
to the range of colour shown by Beryl, there are a number of minerals
which may have to be distinguished from it. Of these, all but Quartz
are more dense. Yellow Quartz may be mistaken for Golden Beryl, but the
Quartz is lighter and also shows less dichroism and is rather softer.
Of the remainder, green Corundum may have to be distinguished from
Emerald, yellow Corundum from yellow Beryl, and pale blue Corundum from
Aquamarine. The Corundum is denser and of greater hardness. Green and
pale blue Tourmaline may similarly be distinguished from Emerald and
Aquamarine respectively by their greater
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