TOPAZ, in natural history, a gem called by the ancients chrysolite, as being of a gold colour.
The topaz, when perfect and free from blemishes, is a very beautiful and valuable gem; it is, however, very rare in this state. It is of the number of those gems which are found only in the round or pebble form, there never having been yet seen a true and genuine topaz of a columnar figure, though the far greater part of what our jewellers call such are in that form. The greatest part of the true topazes are no larger than grains of a coarse seed; among these there are, however, some met with of the size of a pea, and some much larger, though these are very rare. It is of a roundish or oblong figure in its native or rough state, and usually is flattened on one side; and is generally of a bright and naturally polished surface, tolerably transparent. They are ever of a fine yellow colour; but they have this, like the other gems, in several different degrees: the finest of all are of a true and perfect gold colour; but there are some much deeper, and others extremely pale, so as to appear scarce tinged. The oriental topaz is equal to the ruby in hardness, and is second only to the diamond in lustre. The topazes of the other parts of the world fall off greatly from this hardness; but the purest of the genuine ones are considerably harder than crystal. The topaz on being thrown into a charcoal fire entirely loses its colour; and when taken out, is a very fine colourless stone, undistinguishable from that known by the name of the white sapphire. Upon the whole it appears, that the oriental-coloured gems are much alike in their matter, differing scarce at all, except in colour; and that when they are found either naturally colourless, or rendered so by art, it is not easy to distinguish one of them from the other.
The finest topazes in the world are found in the East Indies; but they are very rare there of any great size: the Great Mogul, however, at this time, possesses one which is said to weigh 157 carats, and to be worth more than 20,000 pounds. The topazes of Peru come next after these, in beauty and in value. The European are principally found in Silesia and Bohemia, and are generally full of cracks and flaws, and of a brownish yellow.
Besides all these degrees of value in the genuine topazes, our jewellers keep what they call a kind of them, inferior greatly to the true ones; all these are common hexangular crystals, coloured to a paler or deeper yellow in mines: these they cut into stones for rings, and sell under the name of topazes; and most of the stones we see under that name are such.