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; rare; collectors’ gem only.
ALMANDITE, See GARNET AMAZONITE, See FELDSPAR AMBER
Mostly supplied by East Germany and Denmark in pieces to 4″ diameter; Burmese and Italian amber rarely available; Dominican amber commonly offered but seldom of good lapidary grade; avoid recent fossil resin copal which is much cheaper than true amber but also crazes quickly and has no place in the lapidary arts.
AMBERDAN
Tests indicate that this is not amber but a suitably colored plastic material closely resembling true Baltic amber in appearance; sold in rectangular blocks.
AMBLYGONITE
Almost colorless to pale straw-yellow to rich yellow cleavage masses from Brazil affording clear areas suitable for faceting; supplies sporadic; soft; rare; collectors’ gem only. Usual size faceted gems 3-15 ct.; record gem of about 70 ct. known.
AMETHYST, see QUARTZ ANALCIME
A common mineral but very rare in transparent crystals sufficiently large to
cut small faceted gems not over 1-2 ct.; soft, fragile; collectors’ gem only.
ANDALUSITE
The clear variety provides beautiful dichroic gems in green-red or brown-red when properly cut; hard, durable, but too rare to be more than collectors’ gems; supplied mainly from Brazil, also Ceylon, as waterworn pebbles and crystals; veil inclusions common; usual size 1/2″, rarely to 100 ct.; cut gems to 5 ct. common but cut gems to 20 ct. rare and valuable.
CHIASTOLITE
Impure variety of andalusite in the form of cigar-shaped crystals to 1″ diam¬eter and displaying black cross-like figures against a white to tan background; soft; sometimes cut as a curiosity.
ANDRADITE, See GARNET ANGLESITE
Extremely soft and fragile lead mineral; rarely in clear crystals large enough to facet; colorless to pale brown; collectors’ gems.
ANTHOPHYLLITE
Sometimes displays a bronze iridescence but rarely available and seldom cut.
ANTHRACITE
Selected masses from Pennsylvania are suitable for carvings and ornamental items but seldom offered and then only at pound prices.
APACHE TEARS, See OBSIDIAN APATITE
Popular among amateur cutters, but soft and requiring care in treatment; abundant vivid yellow crystals from Mexico yielding gems to 20 ct.; small frac-
ture fragments of green and yellow-green available from other sources; Maine purple and Burma blue rare and highly prized; Mexican yellows can be heat-treated to colorless; greenish catseye available from Brazil; collectors’ gem only.
AQUAMARINE, See BERYL ARAGONITE
Rarely in facet-grade crystals only from Bilin, Czechoslovakia, as elongated pale straw-yellow prisms capable of cutting gems to 8 ct.; soft, fragile; collectors’ gem only. Massive material sometimes offered for cabochons but most of this is actually calcite.
ARGILLITE
Soft gray slate-like rock from British Columbia used for carvings but under Indian monopoly and not usually sold.
AUGELITE
Soft, fragile; clear colorless crystals only from Champion Mine, Mono County, California; now unobtainable; collectors’ gem only.
AVENTURINE, See FELDSPAR or QUARTZ AXINITE
Recently in large quantities from Baja California, Mexico, as brown crystals yielding faceted gems to 23 ct.; strongly trichroic; intensity of color makes gems larger than about 5 ct. appear dark; while classed as a collectors’ gem the hardness and durability is sufficient for normal wear in jewelry but the color is commercially undesirable.
AZURITE
Small clean crystals facetable but finished gems must not be over i/88 thick if any light is to be reflected; soft, fragile; collectors’ gem only. Attractive cabochon material sometimes available but most material offered is too porous to permit good polish; alternate bands of azurite and malachite, sometimes AZURMALACHITE, See AZURITE BARITE
Very soft and fragile crystals provide small faceted gems for collectors; com¬monly available from South Dakota, Colorado, and England; massive barite rarely available.