QUARTZ
The numerous varieties of this mineral provide more inexpensive gem material than all other species combined. Crystalline varieties are those with individual crystals large enough to see with the naked eye or under weak magnification; cryptocrystalline varieties require high magnification and typically con¬tain minute fibrous or granular crystals, commonly arranged in parallel group¬ings forming bands. Varietal nomenclature of quartz has been made extremely complex and confusing by the tendency of miners and dealers to affix distinc¬tive names to varieties which actually differ but little from well-established varie¬ties; the result is a long list of names which have little meaning. The list below includes only the standard varieties or those which have been shown to be suffi¬ciently different to deserve their own varietal names.
AMETHYST

Customarily divided into three grades according to decreasing desirability: Siberian, Uruguay, and Bahia, the first being richest and purest in hue with decided change in color from blue-purple in daylight to red-purple under tung¬sten light; supplied mainly by Brazil with smaller amounts from Uruguay, Madagascar, and elsewhere; quality names above are appended to material from any source, providing it meets quality standards. Serious defects in rough include color-banding (usually as colorless streaks alternating with colored areas), variations in color intensity, smoky tinges, and veils of inclusions; attempts to remove smoky color may result in complete loss of amethystine hue as well as smoky tinge. Finest material is rare in sizes over about l”-2″ diameter.
“STAR” AMETHYST
Pale amethyst containing filaments of reddish hematite arranged upon the terminal faces of the crystals; when cut across the crystal tips a fixed six-ray pattern is seen, but the legs of the “star” are merely streaks where the hematite crystals fail to reflect light; apparently only from a single deposit in Mexico.
Single crystal tips
AVENTURINE QUARTZ
Fine-grained quartzites containing numerous mica crystals which impart a spangled appearance when viewed in the appropriate direction; formerly in golden material from Russia but now the best is green material from India and paler green from Brazil; popular for tumbled gems, cabochons, carvings, and ornamental objects.
BINGHAMITE, See TIGEREYE
CACOXENITE, See GOETHITE IN QUARTZ
CAIRNGORM, See SMOKY QUARTZ
CATSEYE QUARTZ
Contains numerous parallel fibers which are finer and less abundant than those in tigereye; cabochon gems show a good to fine straight streak of light; colors yellow, brown, rarely green; mainly from Ceylon; rough not available; also produced by bleaching of tigereye.
CITRINE
Much used in inexpensive jewelry as a substitute for genuine topaz and un¬fortunately often sold under that name; color ranges from faint yellow to deep pure yellow, to golden yellow, to reddish-yellow, and in various shades of yellow¬ish-brown; heat-treated amethyst produces rich reddish material known as Rio Grande citrine, Madeira citrine, and Palmyra citrine, the deeper colored ame¬thysts producing correspondingly deeper colors in the citrine; this material is more expensive than naturally-colored material. The terms ox-blood or sang dt boeuf are sometimes used for natural dark citrines with a decided reddish hue Virtually all citrine is produced in Brazil, but fine material occasionally appear; from Madagascar. Ordinary citrine often occurs in sizes capable of cutting flaw¬less gems over several hundred carats in weight. Most material is facet-cut bm some is employed in cabochons and tumbled gems; large flawed pieces art desirable for carvings.
GOETHITE IN QUARTZ (”Cacoxenite”) The Brazilian material is commonly and erroneously called “cacoxenite” due to an early misidentification of the brilliant yellow to gold parallel goethite fibers and tufts which appear in this variety; the fibers are arranged in layers parallel to the terminal faces of large citrine-amethyst-smoky quartz crystals, the centers of which supply tumbling material, but only the outer zones provide the material herein described; when properly oriented, fair catseye and chatoyant effects are possible.
GREENED AMETHYST, See AMETHYST
MORION, See SMOKY QUARTZ