A Treatise on Diamonds, and Precious Stones/Chapter 2/Section 10
SECT. X.
Zircon—Hyacinth and Jargoon.
The Hyacinth is of an orange red color, and, when free from defects, is a beautiful and brilliant stone. Small specimens are common in Ceylon, where they are cut and polished; they rarely exceed the size of a bean, but they have occurred large enough for brooch stones. As they are generally full of flaws, they are not often employed in jewellery.
THE JARGOON.
Though differing in color, is of the same class with the preceding. It is a transparent stone, greatly resembling colored crystal, but when polished, it has considerably more lustre. A century ago this gem was considered to be a variety of diamond; it was usually set in rings, buckles, and around stones of little value: at present it is seldom used in jewellery, and therefore bears but a very low price.
TOURMALINE.
Tuts stone is remarkable for its electrical properties. It generally occurs in black and opaque crystals; but the precious varieties are translucent, and of a green, blue, or pink color; they are used for ring-stones, brooches, or seals. By heat or friction it becomes elec tric, and may be distinguished by this property, which it retains many hours.
MOON-STONE.
Is a beautiful translucent substance, of a bluish white color, When cut spheroidal, it reflects a strong light, which appears on the surface of the stone, agreeably contrasting with the pale celestial hue of the gem. It is used chiefly for ring-stones and ear-drops. Fine specimens were formerly sold at high prices; but the recent importations from Ceylon have considerably reduced their value.
SUN-STONE
Is a rich variety of aventurine, which reflects a bright flame-like color, when held in a strong light. It is a silicious substance, and owes its peculiar beauty to the arrangement of its particles, or the dispersion of minute specks of mica in ferruginous quartz. It is rare, and much valued by connoisseurs.