62. Brazilian and Saxon, already mentioned.
63. Bohemian.—These are found chiefly in the tin mines of Bohemia, are of small size, deficient in transparency, have only grey or muddy white colours, and are of little value.
64. Blue Topaz.—This is a large Brazilian gem, which varies in size from one or two carats to two or three ounces. A fine blue topaz, without flaw, and which weighed an ounce and a quarter, was sold for 200 guineas. It is sometimes difficult to distinguish a blue topaz from an aqua marine ([68]).
65. Pink Topaz.—Some beautiful rose-coloured varieties of topaz have been brought from Asia Minor, and others are found in South America; but the pink topazes in the jewellers’ shops are chiefly stones of the yellow Brazilian kind, which have had their colour changed by heat.
66. The White, or Nova Mina Topaz, is a perfectly colourless and transparent variety. It generally occurs of small size, and is in considerable estimation in Brazil for ear-rings, or for being set round yellow topazes. Small stones of this description have recently been found at St. Michael’s Mount, in Cornwall.
There is imported from Brazil a yellow kind of crystal ([83]), which is so similar, in its appearance, to the yellow topaz as sometimes to be imposed upon purchasers for that stone.
67. The EMERALD is a well-known gem, of pure green colour, and somewhat harder than quartz.
Its natural form is a short six-sided prism; but it is sometimes found massive, and rounded like a pebble.
By the ancients the emerald was a gem much in request, and particularly for engraving upon. They denominated it smaragdus, and are said to have procured it from Ethiopia and Egypt; but, besides the true emerald, Pliny, under this title, includes green jasper ([96]), malachite ([231]), fluor spar ([194]), and some other green minerals. The pillars of emerald in the temple of Hercules at Tyre, mentioned by Herodotus, and the large emeralds described by Pliny as having been cut into columns and statues, cannot be referred to the true emerald.
The deepest coloured and most valuable emeralds that we are acquainted with are brought from Peru. They are found in clefts and veins of granite, and other primitive rocks; sometimes grouped with the crystals of quartz ([76]), felspar ([110]), and mica ([123]); and, not unfrequently, loose in the sand of rivers. The most ancient emerald mine is that of Manta, in Peru, but it has been some time exhausted; and most of the emeralds that are now brought to Europe are obtained from a mine situated in the valley of Tunca, between the mountains of New Grenada and Popayan.