HIS
term is now applied to all the violet and purple crystals of Quartz,
which, when fractured, present the peculiar rippled or undulated
structure described by Sir David Brewster. The stone called Oriental Amethysi, is strictly a variety of Sapphire, of violet colour, but the term is applied commercially to any Amethyst of exceptional beauty.
Amethyst
is a variety of Quartz said to contain traces of oxide of manganese, to
which the violet colour is commonly attributed. When heated, however,
it becomes yellow or white, and may acquire opalesence. The crystals,
like those of quartz in any other of its manifold varieties, are of
sufficient hardness to scratch glass, and are infusible before the
blow-pipe.
The
Amethyst is dichroic, or exhibits under certain conditions two distinct
tints—the one being reddish purple and the other bluish purple.
Amethysts are usually found in association with
Agates. Brazil, Uruguay, and Siberia furnish us with the
best specimens of the dark coloured stones. The common
Amethyst is found in nearly all parts of the world, but is
jof very little value.
To
show the fall in the value of this stone, we may refer to the Amethyst
necklace of Queen Charlotte, which was supplied by my predecessors,
Messrs. Emanuel Bros., of Bevis Marks. It consisted of well-matched and
very
