  Remarkable clearness and transparency, capacity of taking a high polish and hardness and weight greater than that of quartz. These are the qualities in which Topaz excels as a gem. Numerous other stones of inferior quality masquerade under its name, however, and this fact may account for the decline in popularity which the stone has suffered in recent years. True Topaz is a silicate of alumina, containing hydroxyl and fluorine. Its hardness is 8 in the scale in which quartz is 7. Hence it will scratch the latter mineral and may thus be distinguished from it. It is also remarkably heavy, considering its composition, it being three and one-half times as heavy as water, while quartz is only two and one-half times as heavy. Owing to this unusual specific gravity, experts accustomed to handling gems can frequently pick out the Topaz from a miscellaneous lot of precious stones without removing their wrappings. The color typically associated with Topaz in its use as a gem is yellow. Yet the mineral species exhibits many other shades of color, which, when present in crystals of sufficient clearness and purity, answer equally well for gem purposes. These other shades, most of which are represented in the accompanying plate, are grayish, greenish, bluish and reddish. Topaz may also be quite colorless. The yellow color of the Brazilian Topaz can be changed by heating to a pale rose pink and the gem is often treated in this way. The degree of heat employed is not high, and both heating and cooling must be performed gradually. Warming in a sand bath at a low red heat is the method usually employed, or the stone may be wrapped in German tinder and the latter set on fire. Only stones of a brown yellow color yield the pink; the pale yellow stones turn white when so treated. Once the pink color is obtained it is permanent. The natural colors of Topaz are in general perfectly durable, although some of the deep wine yellow Topazes from Russia fade on exposure to daylight. Topaz is infusible before the blowpipe. It is not affected by hydrochloric acid, but is partially decomposed by sulphuric acid and then yields hydrofluoric acid. If the latter experiment is tried in a closed glass tube the formation of the hydrofluoric acid is made evident by the etching and clouding of the walls of the tube. The powdered stone should be mixed with acid sulphate of potash for this experiment. The powdered mineral, when heated with cobalt nitrate, assumes a fine blue color, due to the alumina which it contains. One of the most convenient means of distinguishing Topaz from other stones used to imitate it is through its property of becoming electric by heat, friction or pressure. This electrical condition is evidenced, as in the case of tourmaline, by the power the stone acquires to pick up and hold bits of tissue paper, straws, etc. Sometimes the friction from merely rubbing the stone between the fingers will be sufficient to produce this electrical condition, while many Brazilian Topazes, if simply pressed between the fingers, especially in the direction of the prismatic axis, become electric. The electrical condition often persists from twenty-four to thirty hours. The crystals of Topaz belong to the orthorhombic system of crystallization. They are usually elongated in the direction of the prism and have sharp, bright faces. They vary much in size and often are large. One crystal weighing twenty-five pounds was found in Siberia. A well-marked characteristic of all Topaz crystals is their tendency to cleave across the prism parallel with its base. Such a cleavage plane can be seen cutting across the crystal shown in the upper right-hand corner of the accompanying plate. This cleavage is so marked and the cleavage plane so bright and flat that in cutting Topaz for a gem a cleavage surface is used as the upper face of the gem and the other faces formed around it. Owing to this easy cleavage the owner of a cut Topaz should be careful not to let the stone drop, as it might be cracked or broken. TOPAZ.
The name Topaz is derived from the Greek name topazios, which is that of an island in the Red Sea. The gem known to the ancients as topaz, however, was not our Topaz, but the mineral chrysolite. Topaz usually occurs in gneiss or granite, with tourmaline, mica, beryl, etc. In Brazil it occurs in a talcose rock or in mica slate. It is sometimes in sufficient abundance to form an essential rock constituent. When so occurring, however, it has not the transparent gem quality, but is white and opaque. Much of the Brazilian Topaz occurs as rolled pebbles, one of which is shown in the accompanying plate. These occur in the beds of streams, having been left behind owing to their superior hardness after the rock in which they were formed has been washed away. When colorless they are known in the region as “pingos d’Agua” (drops of water). The Portuguese call them “slaves’ diamonds.” A stone in the crown of Portugal, reputed to be a diamond of 1,680 carats weight and called the Braganza, is undoubtedly only a Topaz of exceptional clearness and beauty. The Brazilian Topazes come mostly from the Province of Minas Geraes, the province which also yields diamonds, beryls and many other precious stones. While those of greenish and bluish shades are found mostly in the form of rolled pebbles the yellow Brazilian Topaz is found in the mother rock. This is a decomposed itacolumite of a white or yellow color. The Russian Topazes, like that shown in the plate, come from the Imperial mines in the Urals. Alabashka, near Mursinka, is one of the most productive localities. The crystals occur in cavities in granite and are accompanied by crystals of smoky quartz, feldspar and mica. Superb gems are cut from these Topazes, a fine series of which is possessed by the Field Columbian Museum. The mines are operated by the Russian Government and the finest specimens are reserved for the Imperial Cabinet. In the southern Urals, in the gold washings of the River Sanarka, yellow Topazes are found closely resembling those of Brazil. Associated with them are amethysts, rubies, chrysoberyls and many other precious stones. Topaz crystals of good size and color are found quite abundantly in Japan, although they have not yet been cut for gems to any extent. There are many localities in the United States where Topaz occurs, and it is often of gem quality. The group shown in the plate illustrates its occurrence at Thomas Mountain, Utah, a locality forty miles north of Sevier Lake. The crystals are found in cavities in the rock. They are never very large, but are usually clear and bright. They occur in somewhat similar fashion at Nathrop, Colorado. In the Eastern States Topaz was first found at Trumbull, Conn. It is here quite opaque and not suitable for gem purposes. Good gem Topaz has been found at Huntington and Middletown, Conn., however, and especially at Stoneham, Maine. In these localities it occurs in granite. Of other stones which are sold under the name of Topaz the most common is the so-called Spanish or Saxon topaz. This is simply smoky quartz heated until it turns a yellow color. It can easily be distinguished from true Topaz by the properties above given. At the present time it is also quite the common practice to vend ordinary colorless quartz under the name of Topaz. These practices are harmful to the reputation of true Topaz, as these forms of quartz are common and cheap and lack many of the desirable qualities of that stone. There is also a so-called Oriental Topaz which is a yellow form of corundum. It is heavier and harder than true Topaz, but its color and luster are not generally considered as desirable as those of that mineral. About forty years ago Topaz was quite popular as a gem and commanded three or four times its present price. At the present not more than two dollars a carat is often paid for the stone. Topaz is often referred to by ancient writers and is mentioned in the Bible as A Topaz presented by Lady Hildegarde, wife of Theodoric, Count of Holland, to a monastery in her native town, emitted at night, according to legend, a light so brilliant that in the chapel where it was kept prayers could be read at night without the aid of a light; a statement which might well be true if the monks knew the prayers by heart. The spiritual qualities associated with Topaz are fruitfulness and faithfulness. It is also said to confer cheerfulness upon its wearer. The ancients believed that it calmed the passions and prevented bad dreams; that it discovered poison by becoming obscured when in contact with it; that it quenched the heat of boiling water, and that its powers increased and decreased with the increase and decrease of the moon. Also a Topaz held in the hand of a woman at childbirth was believed to lessen suffering. Lastly, a Topaz is the gem of the month of November: “Who first comes to this world below With drear November’s fog and snow Should prize the topaz’s amber hue, Emblem of friends and lovers true.” Oliver Cummings Farrington. |
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