Page:Popular Science Monthly Volume 41.djvu/682

664 sheet, we can get the garnet-plate set in mica, and it makes a specimen well worth preserving. Less frequently one finds a thin layer of quartz imprisoned between the mica, or a thin layer of the transparent glassy feldspar known as sanidin. Sometimes the mica itself is microscopically striated, and plays queer tricks with the light, giving iridescent films that might easily be mistaken for soap-bubbles.

But the feldspar is the most promising matrix for the mineral hunter. At the Cloudland mine it is well penetrated with the greenish, yellowish, and bluish hexagonal prisms of the beryl. The precious form of this mineral, the emerald, is seldom or never found in the mica mines. There is, however, an intermediate variety known as the aqua marine, which occurs in the mines around Spruce Pine, and is somewhat esteemed as a gem. As the name indicates, it is of a light sea-green color. It is perfectly transparent, and when well cut makes a quiet but really beautiful gem-stone. Clear crystals of aqua marine are exceedingly rare. It comes commonly as a part of the opaque crystal of beryl.

Intimately associated with the beryl are plentiful sprinklings of blood-red garnets, and the two colorings against the pure white background of the feldspar make a very effective combination. Garnets are generously distributed in nearly all the mica mines, and add much to the beauty of these mineral masses. One day at the Cloudland mine, a large mass of feldspar was blown down, and there in the center of the white and standing face of the vein was a blood-red spot at least six or seven inches in diameter. A giant garnet had been cut squarely in two by the blast, and the blood-red spot was a cross-section of what remained.

In other mines, such as the Tolly Bend in Yancey County, the white feldspar is occasionally covered with patches of dainty pink. It is the mineral rhodonite, a silicate of manganese, and is as delicate as a peach-blow vase.

There are also other accessory minerals which are less striking in appearance, but of greater scientific interest on account of their rarity. Such are euraninite, gummite, columbite, and samarskite, containing the rare metals uranium, columbium, yttrium, tungsten, tantalum, and their allies, which are curiosities even to the chemist. At Spruce Pine, one gets excellent specimens of uraninite, the oxide of uranium. It is a heavy black mineral with a frequent orange-yellow coating of another uranium compound, gummite. The miners take considerable interest in finding the mineral, as it is worth something like a couple of dollars a pound, and it takes a very small quantity to make a pound. The oxides of the metal are used to produce black and yellow