TIGEREYE
Narrow seams of an asbestos mineral replaced by quartz; the original fibrous structure is retained, resulting in chatoyancy in polished specimens; yellow, brownish-yellow, brown, red, blue, green, and streaked in these colors; yellow is by far the most abundant kind; supplied exclusively from South West Africa. Brown and yellow kinds turn red upon heat-treatment; they can also be turned to very pale yellow by bleaching in warm oxalic acid solution. Binghamite is a ligereye from the iron deposits of Minnesota; its fibers are much finer and chatoyancy sometimes greater. Silkstone is analogous to binghamite but the fibers are randomly oriented and it is not so highly prized. African tigereye used extensively in cabochons, engraved eems, tumbled gems, and ornamental items.
TOURMALINATED QUARTZ
Clear to smoky quartz containing slender black tourmaline needles; the value depends on uniformity of size of needles and even distribution throughout the quartz; the needles should not be too fine or too abundant; sometimes used for cabochons and carvings.
BANDED AGATE
Major source continues to be the Brazilian-Uruguayan basalt field producing nodules from walnut-size to 10″-12″ in diameter; much is dull gray material but some is fairly colorful with good bands; finest colored material is being provided by the Mexican fields.
BLOODSTONE
An extremely dense, dark green moss agate in which appear more or less circular spots of dark red or so-called “drops of blood.” India is virtually the only reliable source. Finest material shows a uniform green groundmass with evenly-spaced red dots.
CARNELIAN
Translucent chalcedony of brownish-red, red, or red-orange color; sard is dark reddish-brown, sardonyx is sard with white bands; natural brownish car-nelian often improved in color by heat-treatment; most vivid red-orange mate¬rial is heat-treated Indian carnelian; much carnelian from Idar-Oberstein is dyed.
DYED CHALCEDONIES
Finest grades dyed with permanent pigments and are uniformly colored, free of flaws, and mostly translucent; mainly supplied by Idar-Oberstein, Germany, in slabs; rough used is Brazilian agate and chalcedony.
CHERT AND FLINT
Chalcedonic materials of sedimentary origin; usually less translucent than chalcedonies deposited during volcanic activity; rarely display banding but may have attractive patterns and colors resulting from stains.
CHRYSOCOLLA CHALCEDONY
Translucent chalcedony colored attractive blue-green to green by copper min¬erals; finest material uniformly colored, free of inclusions, and highly translu¬cent; some can be faceted into “sleepy” gems; principally from Arizona.
CHRYSOPRASE
Finest known material now comes from Australia and in respect to intensity of hue and quality far overshadows chrysoprase found elsewhere; the best Aus¬tralian material is translucent, completely uniform in hue and texture, and is free of pale spots or small quartz-filled vugs.
CORAL (Silicified) Primarily supplied by Florida in the form of geodes lined with chalcedony of various colors; also solid coral showing coral markings, from Iowa and Utah; mainly used as polished specimens and for tumbling
DENDRITIC AGATE, see also MOSS AGATE
Finest types display black, red, or brown inclusions resembling miniature trees, in translucent chalcedony; the best come from India but also occasionally fine from Montana and elsewhere.
DINOSAUR BONE
Dinosaur bones replaced by chalcedony and showing cell structure quite clearly; very variable in quality, solid material being quite rare.
EYE AGATE
Two types of agate are called by this name: (1) any banded agate cut in such a manner that the exposed bands form circular rings, and (2) any agate con¬taining tube-like structures which show rings when cut across in the proper direction; the first type is usually cut and polished as a first step and then dyed to impart color to some of the rings. The specimens are then used for display purposes.
FIRE AGATE
Chalcedonies which contain very thin bands of iridescent goethite; when properly cut the iridescence appears near the surface showing reddish, brownish, golden, and greenish colors; the best material is highly translucent because this detracts least from the iridescence; prices vary greatly depending on intensity of colors.
IRIS AGATE
Because the beautiful colors of this variety are seen only in transmitted light, this material seldom is used in jewelry but finds some employment in screens, lamp shades, or other transparencies through which light will be shown; the finest material is highly translucent, displays vivid colors, and the color bands are at least l/g” wide; prices vary greatly dependingon intensity of color, width of color bands, and if the slice is a complete nodule section.
JASPER
A convenient catch-all term for all forms of impure chalcedony which con¬tain so many inclusions that the material is usually translucent only on thin edges; many colors and patterns available; much jasper occurs in blocks of large size; common defects are hairline cracks, small quartz crystal-lined vugs, and porous spots which refuse to polish. Only a few varieties are listed below.
LACE AGATE
Applied to banded agate in which the bands zigzag on a small scale and re¬semble the scallops of lace edging; “crazy lace” from Mexico is porous and ac¬cepts organic dyes.
MONTANA AGATE
Characterized by brownish-red bands and/or black dendritic inclusions in translucent pale gray to bluish-gray chalcedony; nodules and fragments in gravels of Yellowstone River Valley, Montana; favorite ring stone in Western U.S.
MOSS AGATE
Contains dark green, brown, yellowish, or red wispy inclusions in translucent chalcedony resembling the filaments of moss; finest qualities display evenly spaced filaments which do not undercut during polishing; major supplies from India but common elsewhere.
NOVACULITE
Gritty sharpening stone quarried in Arkansas and sometimes providing hand¬some cabochon material; difficult to polish to high luster.
OOLITE and ALGAE
Minute silica spherules (oolite), usually not over 1/16″ diameter; seldom at¬tractive unless the spherules are distinctly colored; dark brown wavy patterns characterize algae.
PETRIFIED WOODS
A large variety of silicified woods are available, ranging from enormous logs to branch and twig sections, and from dead-black or white to reds, yellows, tans, browns, and other hues; common defects are fractures, soft spots, and small quartz crystal vugs; some woods contain opal in addition to chalcedony and are difficult to polish well because of hardness differences; most specimens used for large ornamental objects but much is also tumbled; the region surrounding the Petrified Forest in Arizona supplies most market demands.
PLUME AGATES
The finest grades provide very attractive cabochons if the feather-like inclu¬sions are enclosed in translucent chalcedony; prized plume colors are red, yel¬low, orange, and black; the last is satisfactory only if the plumes are not too dense; quality depends on even spacing of filaments, absence of soft spots, brightness of plume colors, and degree of translucency of enclosing chalcedony; fine examples are not common.
PSILOMELANE CHALCEDONY
Chalcedony containing abundant minute plumes of a black manganese min¬eral arranged in bands, some bands polishing to a brilliant metallic black; also called “crown of silver,” and erroneously, “black malachite.” Now used as a substitute for hematite.
SAGENITE
Chalcedony containing numerous straight needle-like inclusions, often radi¬
ating from common centers; rare in fine grades; commonly undercuts.
THUNDEREGGS
These nodules are mostly used as specimens when sawn into halves and polished; occasionally the interior material contains plumes and is then used for cabochons.
TURRITELLA
Large numbers of conical spiral shells, about yA” long, replaced by silica in a dark brown groundmass; principally supplied by Wyoming.
End of Quartz—Cryptocrystalline Section
RHODIZITE
Very rarely as small clear crystals and fragments up to i/s” diameter suitable for faceting; pale yellow; from Madagascar only; extremely rare in facetable pieces.
RHODOCHROSITE
Beautiful massive material only from Catamarca, Argentina; used for cabo-chons, beads, and ornamental objects; rarely, facet-grade crystals from Colorado; soft and brittle but massive material fairly tough. Stalactite sections from Ar¬gentina are particularly prized as specimens because of their handsome con¬centric ring patterns.
RHODOLITE, see GARNET RHODONITE
The richest colored material now comes in quantity from Australia; fine red from California no longer available; attractive pink available in quantity from Vancouver Island, Canada; very rarely, facet-grade crystals are found with galena at Broken Hill, New South Wales.
RHYOLITE
Some silica-rich rhyolites are attractively banded in several colors, as reds, browns, tans, purples, etc., and take a fair to good polish; the name wonder-stone has been applied to them.
RICOLITE, see SERPENTINE ROCK CRYSTAL, See QUARTZ ROSE QUARTZ, See QUARTZ RUBELLITE, See TOURMALINE RUBY, See CORUNDUM RUTILATED QUARTZ, see QUARTZ
RUTILE (Natural and Synthetic)
Natural rutile crystals are seldom large and clear enough to afford faceted gems; some have been cut from slender crystals from North Carolina and from twin crystals from Brazil. Synthetic rutile, commonly called titania, is available in boules, boule sections, and preforms; full boules run about 200 ct. and are usually very pale straw color.
SAGENITE, see QUARTZ
SAMARSKITE
A black, heavy, rare-earth mineral sometimes cut as a collectors’ curiosity.
SANIDINE, see FELDSPAR
SAPPHIRE, see CORUNDUM
SARD, see QUARTZ SARDONYX, See QUARTZ
SATIN SPAR, see CALCITE or GYPSUM
SCAPOLITE
While somewhat soft for use in jewelry, clear scapolite provides attractive faceted gems, while catseye varieties provide handsome cabochons; rough crys¬tals commonly deeply etched and should be examined carefully before purchase; facet-grade yellow available from Brazil; catseye rough from Burma sometimes available.
ICHEELITE
A sought-after collectors’ item, providing highly refractive and dispersive gems; pale yellow, orange, or colorless; soft; clear crystals rare; largest faceted terns seldom over 15 ct.
SEPIOLITE (Meerschaum)
White, porous material, much used for smokers’ pipes and small carvings; usually sold to dealers by the box according to volume.
SERPENTINE
Embraces a wide variety of rock-like ornamental materials ranging from those used for decorative paneling in building interiors, to the finer and rarer kinds suitable for use in jewelry. Verde antique is a dark green rock much used for larger ornamental applications; ricolite is an attractively banded material of predominantly grayish to yellowish-green hues and available in large blocks; bowenite (”Soochow jade”) is a fine-grained translucent type suitable for carv¬ings and some jewelry cabochons; williamsite is the finest serpentine of all when it is highly translucent to nearly transparent, and colored a vivid pure green; some williamsite is clear enoueh to facet.
SHELL
The shells of a number of salt-water and fresh-water mollusks provide attrac¬tive material for inexpensive jewelry, ornaments, carvings, and utensils; the texture is fine and permits delicate carving and engraving; mother-of-pearl or nacre displaying pearly iridescence is prized for knife handles, small spoons, and carvings; non-nacreous shell provides cameo material if it contains layers of contrasting color. Shells listed below are seldom readily available to amateurs but may be obtained from dealers catering to shell collectors; however, samples bought from them are carefully selected for lack of damage and are therefore sold at much higher prices than the unselected commercial shells which are handled without regard to superficial damage. For further details on the species named and their uses in ornament, consult Julia Ellen Rogers’ The Shell Book (1910, 1951).
PEARL SHELL (Pinctada) This is the standard pearly shell much prized for knife handles, veneers, in-ays, and carvings, particularly because of its fine iridescence, thickness and ireadth; large quantities are obtained in Australian waters but the finest speci-riens (P. maxima) are obtained from Tahitian waters; also fine is P. margari¬tifera from Australian waters.
FRESH-WATER PEARL MUSSELS (Unio)
These were formerly fished in large quantities from the rivers in the Mississippi drainage for the sake of pearl-button nacre, but the industry has now greatly declined; adequate supplies can still be obtained by visits to fishers still in busi¬ness or from shell dealers; very many species available.
TOP SHELL {Trochus) Conical spiral shells with wide base 21/£”-5″ diameter; beautiful nacre; the %reat top shell listed below is much used for ornament manufacture in the South Sea Islands and for the making of small nacre articles; produced in large quantities from Australian waters.
GREEN SNAIL SHELL (Turbo)
The T. marmoratus is also fished from Australian waters in large quantities tind exported for the manufacture of pearl buttons and other articles; the nacre Is thick and of good quality; up to 10″ long.
ABALONE (Haliotis) The beautifully colored and iridescent abalone shells have been used for icnturies for decorative and utilitarian purposes; small bits are used for inlay work and in jewelry, particularly by the Indians of the Southwestern United Slates; the whole shells have been used as ornaments and ashtrays. Abundantly mipplied from Baja California, Mexico, and California; principal species are I lie red abalone, H. rufescens, and the green abalone, H. fulgens; mature indi¬viduals attain shell sizes of 10″—12″ and 7-8″ respectively.
NAUTILUS SHELL
The chambered nautilus (N. pompilius) is a handsome pearly shell much used for ornaments, carvings of great delicacy, small containers, and for the manu¬facture of blister-like “coque de perles”; the latter are sections of inner whorls, cut off flat, and filled with wax or cement to simulate ordinary blister pearls; they are about 3/” x 1″ in size and when set in jewelry are quite effective.
HELMET SHELLS (Cassis)
The species of this genus are much favored for cameos because their white to near-white outer layers resting upon colored under-layers provides the necessary contrast for good cameo work; texture fine and capable of affording excellent detail; only one or two large cameos may be cut from one shell, plus several smaller ones; the first two species named below provide practically all of the material used in the cameo carving industry.
CONCH (Strombus)
The common queen conch (Strombus gigas) of Florida and the West Indies has been used for cameos in which the carved figures appear in pink against a white ground; the pink tends to fade in time; abundant and cheap when bought in quantity.
“CATSEYES” (Turbo petholatus)
The snail-like South Pacific mollusk, Turbo petholatus, provides the so-called “catseyes” which are cabochon-shaped calcareous trap doors used to protect the mollusk when the body is withdrawn into the shell. Many of these trap doors are handsomely colored and have been extensively used for ornament among the island natives.
SIDERITE
Brown to greenish-brown cleavable iron carbonate; rarely transparent and then
sometimes used for small faceted gems for collectors; soft and weak.
SILICON CARBIDE (Carborundum)
Sometimes thin crystal blades of this synthetic abrasive are pale enough
SILLIMANITE, see FIBROLITE SILVER IN MATRIX
Dendrites of silver with sulfides occur in calcite matrix in some of the silver deposits of Ontario; suitable sections have been cut for cabochons and ornamental items; readily tarnishes; difficult to polish; soft; collectors’ item only.
SIMPSONITE
Facet-grade yellow-orange crystals from Brazil; hard, high refractive index; very rare; clear areas not over 4 mm.; collectors’ gem only.
SINHALITE
Rare gem mineral found as waterworn pebbles in gravels of Ceylon; mostly
pale straw-yellow to yellow-brown; pebbles to 11/2″ diameter; collectors’ gem only.
SMALTITE
Sulfide mineral providing attractive silvery cabochons; available in large masses from Ontario silver mines; collectors’ item only.
SMITHSONITE
Massive, fine-grained material in many hues as yellow, pale brown, reddish-brown, green, blue; translucent thick-banded types favored for cabochons; some highly translucent types are capable of being faceted into small “sleepy” gems; also in pale straw-yellow crystals of facet grade but very rare; soft but fairly tough when massive, brittle in crystals; massive types formerly cut for com¬mercial cabochons but now mostly in demand by collectors; sources Greece, Sardinia, Mexico, New Mexico, South West Africa, Australia.
SMOKY QUARTZ, See QUARTZ SODALITE
Rich blue cabochon material; Ontario material veined with white, pink, cream, also with yellow cancrinite; recent Brazilian material blue with small white specks and much darker; soft and brittle but useful for heavier cabochons, carv¬ings, and tumbled gems; available in large blocks from Brazil; very rarely, small (to i/s”) facet-grade areas in Ontario material.
SOOCHOW JADE, See SERPENTINE SPECTROLITE, See FELDSPAR SPESSARTINE, see GARNET SPHALERITE
Despite softness and fragility, fine faceted gems are prepared from transparent crystals of yellow, orange, red, or green color; brown hues result in dull gems; abundant fine material from Spain and Mexico; very pale greens from Franklin, New Jersey (cleiophane), provide exceptionally beautiful gems, but material is extremely rare; largest faceted Spanish gems to about 100 ct., but most are less than 40 ct.; collectors’ item.
SPHENE
Once classed as quite rare but recent supplies of material from Baja California, Mexico, and from Brazil have made rough readily available; soft and brittle but high refraction and dispersion provide extremely attractive faceted stones when color is pale yellow, green, or greenish-yellow; occasionally used in jewelry but mainly a collectors’ item.
SPINEL
Available only in small rough because large fine crystals are cut in Ceylon and Burma as produced; in many colors including prized reds, red-oranges, and blues; also pink, grayish-purple, medium purple, dark wine-red, pale gray-blue; hard and tough; synthetics produced in great quantity.
SPODUMENE
Because of difficulties in cutting and lack of strong colors, most varieties are not favored for commercial gems; pink to purple kunzite is the most attractive variety but suffers from color-fading; true hiddenite occurs only in very small crystals in North Carolina and is unobtainable; its name has been applied care¬lessly to pale greenish varieties from Brazil and elsewhere which do not approach true hiddenite in color; Brazil also provides multicolored specimens, sometimes to hundreds of grams in weight and not infrequently flawless; readily cleaved but hard and quite durable.
STAUROLITE
Small cruciform crystals are cleaned and polished as good-luck charms; rarely in facet-grade crystals from Switzerland and then seldom capable of providing gems over i/2 ct.
STIBIOTANTALITE
A rare mineral and even more rarely providing small faceted gems from clear areas; reddish-brown to honey-yellow; hard; cut only for collectors; sometimes available from mineral dealers; from California or Mozambique.
STICHTITE
Pale lilac to purple massive mineral forming narrow veinlets in green serpen¬tine and sometimes cut in cabochons for collectors; soft and difficult to polish well.
STRONTIUM TITANATE (”Fabulite”)
Colorless synthetic facet-grade boules provide beautiful gems to 50 ct. showing high refraction and dispersion; closest in appearance to diamond because of lack of color, presence of high dispersion, high refractive index, and lack of double refraction; soft and brittle; all output in United States channelled through one firm for cutting and distribution of gems under name of “fabulite”; some small boules have been produced in Japan.
TAAFEITE
An excessively rare mineral found in pebbles in the gem gravels of Ceylon; so scarce that rough is never offered for sale.
TEKTITES
Glass-like materials of meteorite-impact or celestial origin; most are black but some are deep green and have been cut into faceted gems for collectors; fairly soft and brittle. Bright yellow-green glasses left over from assay tests for precious metals and resembling small spheres or cones of about ?/4″ diameter, usually with scaley outer layers, have been sold to the unwary as tektites; they quickly develop whitish powdery surfaces, even after polishing.
THAUMASITE
A fibrous white zeolite; when compact, forms dense fibrous masses capable of
polishing into cabochons or beads; the latter are slightly chatoyant; soft; col¬
lectors’ item only.
THOMSONITE
A fibrous mineral filling small cavities in eruptive rocks; sometimes beautifully colored in rings of pink, red, white, and green; quality depends on color con¬trast, patterns, and size of nodules; translucent grayish-green variety showing no patterns whatsoever is known as lintonite. Soft but fairly tough; used to limited extent in jewelry, particularly in Great Lakes region where produced.
THULITE, See ZOISITE THUNDEREGG, See QUARTZ TIGEREYE, See QUARTZ TITANIA, see RUTILE TOPAZ
Most expensive when hues are purplish-red or strong reddish-orange, the latter often called “imperial”; also expensive when natural pink or purple; fine blue rough is costly when similar in color to fine blue aquamarine; sherry-color topaz crystals occur in cavities in rhyolite rocks and are seldom over II/2″ in length, but similarly colored crystals from pegmatite pockets, while much larger in size, also fade upon exposure to strong light; colorless topaz crystals, very faintly yellow or very faintly blue, sometimes reach sizes in excess of 20 pounds, but the material is little valued for cutting. Hard, but with one perfect cleavage, sometimes difficult to polish well; veil-type inclusions common; avoid pieces with cleavage traces.
TOURMALINATED QUARTZ, See QUARTZ
TOURMALINE
The following varieties commonly appear in the gem trade: rubellite, rich red to purplish red; indicolite, deep blue; green, in many shades and tints; pink, and dravite, a dark orange-brown variety. Bi-color crystals also occur, usually in green and red or pink; sometimes good specimens can be cut into very attractive emerald-cut gems. Numerous fine tubular inclusions also result in catseye varieties, mainly in greens but also in pink and blue. Rubellites are generally most expensive if relatively free from flaws and not too dark in color, the cost increasing as the color approaches that of ruby; also expensive are fine greens which are free of any trace of olive and which resemble the emerald in hue; pale blues are quite rare and also highly prized. Achroite, the colorless variety, is extremely rare but only in demand by collectors. Good yellows are also rare, especially in pieces large enough to cut gems of about 6 carats or over; however, the gems are not in demand because they too closely resemble citrine and golden beryl. Good sharp catseyes are in demand and suitable rough is quite expensive. Practically the sole commercial source of tourmaline is Brazil, but fine material occasionally comes from Madagascar, Mozambique, California, and Maine. A small quantity of green and dravite tourmaline is produced from the gem gravels of Ceylon.
CABOCHON, CARVING, AND TUMBLING TOURMALINE
By far the greatest quantity of colored tourmaline contains numerous flaws, usually veil-type inclusions and small cracks, which render the crystals unsuit¬able for facet work but permit use for cabochons, carvings, and tumbled gems. The finest non-facetable material in large sizes is reserved for carvings, smaller sizes being used for cabochons. In general, the prices follow the trends noted above for facet-grade material in the several prized colors.
TREMOLITE (see also NEPHRITE)
Rarely in small clear crystals which can be faceted; also in catseye-type crystals which produce weak streaks of light. The pink variety, hexagonite, from New York State, sometimes occurs in clear crystal grains capable of faceting into gems of about 1/2 carat. Rare; collectors’ gem only.
New York, hexagonite, crystals to 1/2″ long ct. 1.00-2.00
TURQUOIS
Large quality differences exist in turquois from different localities and even in the material mined from a single deposit. In general, seam or vein turquois is poorer in quality than nodular turquois, the latter usually being harder, less porous, and capable of taking a better polish. The finest turquois is still produced by the Iranian mines, but sometimes equally good material is found in some of the deposits of the Southwestern United States. Much porous ma¬terial from the United States is plastic-impregnated after being tumbled to baroque form; the impregnated kinds can usually be recognized by their glassy polish, which is due to the plastic. Pale colors ordinarily mean that the material will refuse to polish well. Top-grade Persian material, especially in larger, “clear” pieces, is seldom sold in rough form.
TURRITELLA, See QUARTZ ULEXITE
Too soft and too easily affected by atmospheric moisture to be considered a gemstone; nevertheless, attractive cabochons and spheres, showing catseyc streaks, are prepared from chatoyant seam sections found in borate deposits ol California; the same material provides the well-known “television stone.”
UNAKITE
Granitic rock containing evenly-spaced patches of salmon-pink feldspar and bright green epidote with some quartz; a popular material for tumbled gems.
VARISCITE
The beautiful pale green nodules from Fairfield, Utah, seldom appear on the market; major supplies are now coming from seam-type deposits in Utah and Nevada, of which the best grades are deep green, translucent, and take a good polish.
VERDE ANTIQUE, See SERPENTINE VERDITE
Occasionally offered from the Republic of South Africa; the original verdite is a compact rock consisting mainly of opaque green serpentine, but some new material, called by the same name, is apparently a quartzose rock colored by fuchsite mica.
VESUVIANITE, See IDOCRASE VIOLANE, See DIOPSIDE
WILLEMITE
Massive, fluorescent material, usually mixed with fluorescent calcite and non-fluorescing franklinite and zincite, is still available from the zinc deposit at Ogdensburg, New Jersey; it finds some use for spheres, flats, and occasionally for unusual cabochons; solid willemite suitable for cabochons is rarer and costlier, while transparent willemite is very rare and is obtained only from old collections; a collectors’ gem.
WITHERITE
Some fibrous masses are sufficiently translucent to provide “sleepy” faceted gems if not cut too large; abundant in pale straw-yellow crystal aggregates from Illinois and more translucent whitish aggregates from England.
WOIXASTONITE
Fibrous aggregates are sometimes compact enough to be cut into weakly chatoyant cabochons.
WONDERSTONE, See RHYOLITE WULFENITE
Clear areas in tabular crystals sometimes cut into small transparent faceted gems of very pretty color and fine brilliance despite the extreme softness and fragility of the mineral; a collectors’ gem only.
ZINCITE
Perhaps one of the rarest of all collectors’ gemstones, the only source of clear material being the now-depleted zinc mine at Franklin, New Jersey, from which came a very small quantity of material in the form of bright orange-red seams in calcite-rich ore; the largest known clean faceted zincite is about 20 carats, but the vast majority of cut gems are less than 3 carats; collectors’ gem only.
ZIRCON
Natural zircons predominantly some shade of brown, but colorless, very pale straw, pale brownish-orange, and blue zircons are obtained by heat treatment of suitable brown crystals; supplies mainly from Thailand and Ceylon, the latter providing a wide variety of green shades which do not change color upon heat treatment; faceted gems up to about 40 carats are known, but the rough ordinarily offered seldom provides faceted gems over several carats; hard but easily chipped.
ZOISITE
The fine grained pink variety, known as thulite, is sometimes used for cabo-chons. Recently a very beautiful facet grade variety was discovered in Tanzania of vivid trichroism: purple, blue, and red, or purple, green, and red. Flawless rough to 50 grams has been found, some in crystals and some in crystal fragments.