Quartz is one of the silicas, chemically Si O₂, as is the opal. It is abundant as a colorless, transparent substance; it also appears as a brilliant crystal. The name quartz is from the German _zwerg_, meaning dwarf. Similarly cobalt and nickel are from German words for sprites, the gnomes being little creatures that work the mine of the gods. In its crystalline form quartz includes amethyst, cairngorm, citrine, quartz cat’s-eye, rock crystal, and rose quartz. Another main group in the quartz family is chalcedony, which includes agate, bloodstone, carnelian, jasper, moss agate, onyx, sard, and sardonyx. These stones are used for beads for carving cameos and intaglios. _Sard_ Sard is a very hard, deep orange-red variety of chalcedony. Its name rises from the fact that it originally came from Sardis in Asia Minor. _Sardonyx_ Sardonyx is a variety of onyx in which the alternating layers are of white chalcedony and sard. It can be cut into beautiful cameos. The sardonyx is not to be confused with the sardonics, known for their scornful smile. The latter have no connection with the powers of the stone; they derive their name from the plant of Sardinia, the island off Italy. The plant, we are told, was poisonous, and made its victims sneer while dying. More scientific botanical tales aver that the plant was bitter, so that its taste at once produced contortions of the mouth. In either event, the bitter, superior smile of the sardonic comes from another part of the world than the peaceful sardonyx stone of Sardis, Asia Minor. _Spinel_ Spinel is so called, little spine, from the shape of its crystals. It is a hard mineral, composed mainly of oxide of aluminum, with iron or magnesium. The proportions of the metals determine the color, which ranges from rose pink through green, blue, and purple, to black. The red variety, rare and costly, is sometimes called a spinel ruby. It is also known as a balas ruby, from Arabian _balakhsh_, from the Persian province of Balakhshan, where spinels from pink to orange have long been found. _Topaz_ The topaz ranges widely in color, according as other substances are present in the complex aluminum silicate that is its basis, chemically Al₂Si O₄F₂. It is transparent, crystalline, and may be white, pale blue, or pale green; but the yellow shade (produced by the presence of fluorine) is preferred for use in a jewel. It often develops its crystals in large clusters; the National Museum in Washington has one weighing 153 pounds. Brazilian topaz is genuine topaz. Oriental topaz, however, is a yellowish crystalline corundum; Occidental topaz, a yellow quartz, citrine. Topazolite is a yellow variety of garnet. The topaz is mentioned in the Bible as the ninth foundation stone of the New Jerusalem. It has not entered greatly into literature, being an undramatic stone, and is not usually at its best when combined with others; but it can be so fashioned as to display a serene and quiet beauty. _Tourmaline_