CHAPTER 13
The Techniques of Gems
I have been using the terminology of the field of gems and jewelry, taking it for granted that the meanings would be understood. Perhaps it is time to make these terms more precise.
Definitions
A jewel, or a piece of jewelry, is a costly ornament, especially of gold, platinum, or precious stones; or of stones set in one of these metals.
A precious stone is one highly prized for human adornment. Its value is measured mainly by its beauty, its rarity, and its durability. The precious stones are, by general understanding, limited to the diamond, the ruby, the emerald, and the sapphire. The pearl, though strictly not a stone and far less durable, is nevertheless, because of its beauty and the rarity of superb specimens, included among the precious gems.
A gem is a precious stone of rare quality, especially when cut and polished. All other stones used in jewelry are semiprecious.
Light on the Stones
Stones may be characterized according to their response to light. Lustrous stones are those which catch the light brilliantly and glow almost as though with an inner flame. The cutting of the gem may aid in this effect, as with the diamond. Vitreous stones are of the glassy type, not lustrous. These may be transparent, permitting one to see objects clearly through the stone, like a fine crystal; or they may be translucent, permitting one to see light and shadow but not distinct objects through the stone. When light falls upon such translucent stones as moss agate, moonstone and agate, there is a soft glow.
Or stones may be opaque, permitting no passage of light, like the turquoise. Because of their crystalline structure, even the opaque stones, however, may respond glowingly to light. Sometimes when the stone was formed, tiny cracks or bubbles stayed between the crystals. As the stone is moved, these cracks cause a play of prismatic colors which seems almost the sparking of an inner fire. To the names of such stones the term fire is prefixed; they are extremely rare and beautiful. The Empress Josephine had a fire opal so remarkably aflame that she called it “The Burning of Troy.”