Small pieces or balls are not very valuable, but large perfect specimens command a good price.
Sunstone.
(AVANTURINE FELSPAR.)
Sunstone or avanturine felspar is a variety of oligoclase; grayish-white to reddish-gray in color, usually the latter; containing minute crystals of hematite, göthite or mica, which are imbedded and scattered through the stone, and give forth golden-yellow, reddish, or prismatic reflections. The hardness is 6 to 7, specific gravity 2.56 to 2.72, and lustre pearly or waxy to vitreous.
Sunstones are found near Stockholm, in Finland, the Urals, Ceylon, the Alps, Iceland, the United States, and other places.
Amazon Stone.
(GREEN FELSPAR.)
The Amazon stone is a green variety of felspar, which was first found on the banks of the Amazon River, but now comes from Siberia and the United States. This stone consists of potash, alumina, and silex—is green in color but rarely clean, being discolored in places and usually covered with small white spots.
The Amazon stone is harder than glass, but is scratched by rock crystal. Its specific gravity is 2.5 to 2.6; acids do not affect it, and it melts with difficulty before the blow-pipe.
Labradorite.
Labrador stone or labradorite is sometimes known as opaline felspar, and was first discovered on the island of St. Paul on the coast of Labrador.
Labradorite is translucent to opaque, gray-green or brown in color, and has beautiful chatoyant reflections of brilliant blue, sea-green, and sometimes red and yellow, changing from one color to another. Labradorite is 6 in hardness, has a specific gravity of 2.62 to 2.76; a vitreous to pearly lustre, is brittle, fuses with difficulty before the blow-pipe, and is decomposed by muriatic acid. It is composed of: