IDOCRASE (Vesuvianite)
Relatively abundant in crystals but seldom providing clear areas for faceted gems of over 2 ct.; good cabochon material more common, jade-like material from California being called californite or, sometimes, “California jade.” Fairly hard but mainly cut for collectors.
INDICOLITE, see TOURMALINE

HAMBERGITE
Very rare colorless gemstone; fairly hard but cut only for collectors; facet-grade crystals only from Madagascar but this deposit exhausted, and material now comes only from old collections;  clean gems  to 5 ct. considered large.

FIBROLITE (Sillimanite)
Very rare; hard, but very easily cleaved and few attempts to cut succeed; as waterworn transparent pebbles in gem gravels of Burma; collectors’ stone only.
Burma, facet-grade pebbles, 2-10 ct.    ct.    1.00-2.50
FLINT,   See   QUARTZ FLUORITE
Soft, cleavable, low refractive index, but occurs in many attractive hues and is commonly faceted for collectors; massive purple and white […]

GADOHNITE
A heavy black rare-earth mineral sometimes cut as a curiosity.
GARNET
The species and varieties of this group furnish many fine gems in a wide variety of hues; deposits widespread and some gem-quality garnets continually supplied to the market at relatively low cost; demantoids and spessartines in short supply; recently very fine rhodolite has appeared on the […]

EMERALD, see BERYL
ENSTATITE
Available from India as corroded facet-grade crystals of dark greenish-brown to brown color; also showing 4-rayed star on nearly black background; faceted gems cut to 4-8 ct., but larger gems appear too dark; hard, tough, but cut only for collectors.
EPIDOTE
Abundant rock-forming mineral, sometimes cut in massive form for cabochons or for large ornamental […]

DANBURITE
Hard gemstone suitable for transparent faceted gems but cut only for collectors; colorless crystals abundant from Mexico; rarely, pale yellow waterworn pebbles from gem gravels of Burma.
DATOLITE
Attractive faceted gems cut from very pale yellowish-green crystals; the finest are from Westfield, Massachusetts, and afford flawless gems to 5-6 ct. Unusual massive datolite, colored by copper and […]

CALIFORNITE, See IDOCRASE CANCRINITE
Bright yellow to orange-yellow massive,    usually with  blue  sodalite;   seldom -
occurs large enough to provide pure-color    cabochons over i/2″ diameter;  soft,
brittle; collectors’ item only.
Ontario or Maine, massive    oz.    1.00
CARBORUNDUM, see SILICON CARBIDE CARNELIAN, See QUARTZ CASSITERITE
Bolivia, facet grade, according to size & color
Mexico, wood tin, brownish nodules
CATL1NITE
Soft,  easily  carved  stone  containing  pyrophyllite
reddish […]

BAYLDONITE
Bright chartreuse-green masses occasionally from the copper mines near Tsumeb, S. W. Africa, in cabochon grade; rare; collectors’ gem only.
BENITOITE
Only known source of facet-grade crystals is at Dallas Gem Mine, San Benito County, California; rarely available except in small fragments seldom over 2-3 ct.; relatively soft; collectors’ item. Largest gem known 9 ct.; cut gems […]

ABALONE, See SHELL
ABALONE PEARL, see PEARL in Chapter VII
ACHROITE, see TOURMALINE
ACTINOLITE (see also NEPHRITE)
Rarely in small crystals; hard but easily cleaved; collectors’ gem only.
Madagascar, small dark green crystals, 1/4
AGATE, See QUARTZ ALABASTER, See GYPSUM ALBITE, See FELDSPAR ALEXANDRITE, See CHRYSOBERYL ALGAE, See QUARTZ ALGODONITE
Irregular masses from Michigan copper mines furnish unusual cabochons of metallic luster; […]