Beryl, Emerald and Aquamarine are the same mineral, a silicate of aluminum and glucintnn. The hardness is eight and the cry stals belong to the hexagonal system. Beryl varies from blue through light green to yellow, when it is called °golden beryl,° and forms a gem resembling topaz. If colored a rich green by a little oxide of chromium, it becomes the emerald, a stone which is rarely flawless, but ranks in value with the diamond. The chief source of fine emeralds has long been the mines at Muzo, about 70 miles on a direct line from Bogota, Colombia, where they occur in a black limestone rock. The mine has been worked by Europeans for three centuries, and was previously exploited by the native peoples of the region. The emeralds known to the ancients came principally from Upper Egypt. near the Red Sea. These mines were long abandoned and left unworked, but are now be ing operated on a small scale. Light sky-blue, rich ocean-blue, sea green or greenish beryls are known as aquamarines; the finest examples have come from Brazil and Madagascar. A Brazilian crystal weighed 246 pounds. They also occur in the Urals and Siberia, as well as in Maine, North Carolina and Colorado. Golden beryls are found in Maine, Connecticut and Pennsylvania. A variety of golden beryl found at Rossing in the former German South west Africa has been given the trade name cheliodor.° Phenomenal The name applied to precious stones which change in color or else have a change of light or exhibit some phenomena other than the color itself. Notable among these are the sapphire asteria and ruby asteria; the ruby asteria or star ruby is found in Ceylon and in the ruby mines of Burma, and is a phenomenal gem in high favor. Then come the alexandrite, a variety of chrysoberyl changing from a dark green by daylight to a columbine red by artifi cial light; the chrysoberyl cat's-eye, changing from pale honey yellow to dark brown, and, oc casionally, the alexandrite cat's-eye, green by day and red by artificial light; moonstone, a white feldspar exhibiting the phenomena of lustre, and a white or bluish play of light ; sun stone, in which there are brilliant reflections from the interior of the feldspar or quartz; Labrador spar, labradonite feldspar, which has a rich play of blue, blue-green and yellow, re sembling a peacock feather. All of these are surmised to bring good fortune to the wearer.
Chrysoberyl, which has a hardness of 8.5, is a glucinum aluminate. It is a rare mineral, of various shades of yellow, brown, light green and dark green. One variety contains minute impurities distributed between the layers of the crystal, and these layers are so arranged, by what is termed the °twinning° of the crystal, that when the stone is cut across them light is reflected or condensed into a transverse bright line; such a gem is called a chrysoberyl cat's eye.
Alexandrite is a variety of chrysoberyl, colored by chromium. This name was given by Nordenskjold because the gem had been found on the day the Csarevitch, later Alexander II, came of age, in 1833. It was first discovered in the Ural Mountains at Takowaya, but now occurs in larger gems, up to 70 carats each, in the gem-gravels of Ceylon. It possesses the property of changing from a dark green to a columbine red when exposed to artificial light, thus displaying in turn what were the Russian national colors at the time it was first dis covered.
Morganite is a rose red silicate of beryllium containing manganese, found in Madagascar, being the same in composition as the aquamarine and the emerald, differing only in color. It
possesses the property of becoming phosphores cent as does kunzite, a mineral with which it is associated. It appears in beautiful gems up to 200 carats each. It occurs, also, at Pala, in San Diego County, Cal., in crystals of some size, and example, small and not of good color, are met with at Haddam, Conn„ but not in gem form. The name was given in honor of the late J. Pierpont Morgan.
Zircon, or Hyacinth (jacinth), sometimes called jargon, is a gem of 7.5 in hardness and having a specific gravity of 4.1 to 4.7, occurring brown, yellow, blue, green and white; it is a zirconium silicate. Frequently the white gem is the result of the decolorization of a darker stone. These were frequently rose-cut in the East, and in the 18th century were called °Matura Diamonds.° The color sometimes re turns after decolorization. The chief source of supply has been Ceylon, although many fine gems have been found in Australia and Tas mania.
Topaz is a rather complex silicate of alumi num, occurring in rhombic prisms and possess ing a hardness of eight. It is generally yellow, but other examples are pale blue, pale green, pale brown and white or colorless. The favorite tint is a peculiar yellow known as sherry color. The finest come from Brazil or from the Ural Mountains, but some very handsome ones have been found in Colorado and Utah. The sherry-colored variety, if heated in vacuo, changes to a rich, almost magenta pink, then to a light pink and finally becomes colorless. White topaz is often found in large masses in Ceylon, and in Brazil, where a 23-pound mass was found. Fine blue and cinnamon colored crystals occur in the Urals, in Siberia, Japan, Mongolia and in Colorado, Texas and Maine; the cinnamon-colored variety changes, upon exposure to daylight, to colorless topaz. (See also QuAwrz; nearly all the so called topazes are really citrines—decolorized smoky quartz).
Tourmaline is a complex silicate of alumi num, occurring in prisms of six, nine or 12 sides. It is usually black, but also of trans parent red, green and other colors, often singu larly mingled in the same crystal. The gem is found in Brazil and Siberia, and examples of great beauty are met with at Paris and Auburn, Me., Haddam Neck, Conn., and es pecially in San Diego County, Cal. Mineral ogically it occurs in a great variety of colors and forms; the red is known as rubellite, the blue as indicolite, the white as achroite and the green is called "Brazilian emerald" in Brazil. Wonderful red tourmalines rubellite are found in the Ural Mountains, Russia, and red and other colors in Madagascar. At times the crystal is green on the exterior with a white zone and a red interior, the iron which causes the green hue being neutralized by the manganese in the red color; this strange com bination forms the so-called "watermelon crystal." Tourmaline is probably the most varied interesting mineral, with the exception of quartz, occurring in magnificent gems of green, blue, red, yellow, brown, white and fre quently three or more colors are present in dis tinct zones in various parts of the crystal. Its electric properties, discovered in the 18th cen tury, was discussed in most of the Euro pean learned societies at that time, the name "Aschentrekker" ("Ash-attractor") being given to the mineral in Amsterdam.