A Treatise on Diamonds, and Precious Stones/Chapter 2/Section 5
Yellow, Red, Blue, and White Topaz.
In speaking of the Topaz, a gem of a beautiful yellow color is always understood; it is wine yellow of different degrees of intensity; and the fuller and deeper the tinge, the more the stone is esteemed. In hardness it yields to the spinelle.
There are few gems more universal favorites than the yellow Topaz when perfect: the rich warm tone of its color, the vivacity of its lustre, (which it retains even by the side of the diamond), and its large size compared with many others, are characters which deservedly entitle it to distinction; it bears accordingly a high price when of good quality.
It is chiefly employed for necklaces, ear-drops, bracelets, &c. in suit. No little skill and taste are required in cutting and duly proportioning this gem; the table should be perfectJy symmetrical, and not too large, the bizel of sufficient depth, and the collet-side should be formed in delicate steps. It works easily on the mill, and the lapidaries are in general tolerably well acquainted with it; yet it is uncommon to meet with one well cut.
The yellow topaz varies in price according to its beauty and perfection. A superlatively fine stone, perfect in color and workmanship, sufficiently large for an armlet, or any other ornament, and weighing nearly eighty carats was sold for £100.
Topazes have become more common since our intercourse with Brazil, consequently they are less in demand, and lower in price. A fine stone of sixty carats may be purchased at from £20 to £35; and smaller, calculated for ring stones, at from £2 to £5: but it is not usual to sell them by weight.
THE PINK TOPAZ.
Tue pink topaz is made from the yellow, which, when of intense color, is put into the bowl of a tobacco-pipe or small crucible, covered with ashes or sand: on the application of a low degree of heat, it changes its color from a yellow to a beautiful pink. This is performed with little hazard, and if the color produced happens to be fine, the price is much augmented,
THE RED TOPAZ.
This beautiful gem, which yery seldom occurs naturally, is of afine crimson color, tinged with a rich brown; it is extremely rare, and generally taken to bea variety of ruby, for which I have seen it offered for sale. Its price, from its scarcity, is quite capricious; it has an exquisite pleasing color, very different from the glare of the artificial pink topaz.
THE BLUE TOPAZ
Is also a beautiful gem, of a fine celestial blue color. It has occurred of considerable magnitude; the finest specimen known I brought in the rough from Brazil; when cut and polished, it weighed above an ounce and a quarter. Smaller specimens are not uncommon, and, when light colored, are often taken for aquamarines, from which they may always be distinguished by their greater weight and hardness, &c.
THE WHITE TOPAZ
Is familiarly called Minas Nova. It is a beautiful pellucid gem, and is used for bracelets, necklaces, &c. It possesses greater brilliancy than crystal, and from its hardness has been used to cover paste, &c.; and to form doublets.
- All the varieties have the same hardness and specific gravity.
- See plate of colored stones.
- It possesses this property of changing color by heat in common with the blue and yellow varieties of fluor; it also contains fluoric acid; which may be the cause of the change of color produced by heat.
- Many impositions are practised in forming pink topazes. See appendix.
- This stone, and the yellow topaz before mentioned, now adorn the magnificent collection of Mr. Hope.