TAAFFEITE :

Only since 1945 identified as a distinct mineral ; before taken for a spinel .

A1₄MgBe0₈   

Physical and optical properties :

Colour : pale mauve, pale pink

Transparency : transparent

Lustre : vitreous

Hardness : 8 to 8.5

Density : 3.615

R.I. : 1.719 – 1.723 (+0.007 – 0.003)

        Up to 1.741 – 1.747

Birefringence : 0.004 to 0.009

System : hexagonal

TABASHEER :

Equally called erroneously " Tabasheer opal " .

Variety of amorphous silicon; translucent to opaque of white to bluish white colour .

TAENITE :

Term sometimes used to designate a banded feldspath .

TAGANAITE :

Synonym for aventurine .

TAIMOWITE :

Variety of epidote showing a strong emerald green / brilliant yellow pleochroism .

BLUE TALC :
Prohibited appellation : for a dysthene/cyanite. (Source : Robert M. Shipley)

TALKSCHORL :

German synonym for dysthene .

TALTALITE :

Variety of green tourmaline from Brazil .

TAMA :

Japanese name for jade .

TANGAVAITE ou TANGAWAITE ou TANGIWAITE :

Variety of serpentine-bowenite .

TANZANITE :

Variety of trichroic zoïsite, containing strontium

Ca₂Al₃Si₃O₁₂(OH)

Physical and optical properties

Colour : sapphire blue, blue-violet, violet

              The colour is in 99 % of the cases due to heat-treatment of brown stones

Transparency : transparent to translucent

Lustre : vitreous

Hardness : 6 to 7

Density : 3.34 to 3.36

R.I. : 1.692 – 1.703

Birefringence : 0.006 to 0.010

Dispersion : 0.030

Trichroism : strong : blue, brown or yellow, violet

System : orthorhombic

TAOSITE :

Synonym for corundum .

TASSIE PASTE :

English term. Glass fabricated by James Tassie ( Scottish, 1735-1799 ) containing less lead than strass

TATAYA :

Burmese name for a topaz .

TAURIDAN :

Topaz generally colourless or very light blue .

TAUTOLITE :

Synonym for allanite .

TAWMAWITE :

A variety of Epidote ; chrome containing ; from Mont Tawmaw in Burma ; green to dark green, resembling emerald .

TECALI :

Name given in Mexico to an onyx marble .

TECLA EMERALD :

Commercial English name given to a triplet imitating emerald .

TECTITE :

General name to designate natural glasses of meteoritic origin, like moldavite .

Density : 1.8 to 2.3

TEKTITE :

See Tectite .

TELESIE :

Ancient name for corundum, sapphire .

TELLEMARKITE :

Synonym for a grossular .

TENACEOUS FELDSPAR :
Synonym of Saussurite.

TENNMALN :

Synonym for cassiterite .

TETE DE MAURE :

French term. Variety of tourmaline, colourless or green with a black termination .

TETE DE TURQUE :

French term. Variety de crystal de tourmaline green avec un terminaison red

THALITE :

Variety of saponite .

THALLITE :

Variety of epidote of yellowish green colour ( synonym of delphinite  )

TERMOPHYLLITE :

Variety of antigorite-serpentine .

THETIS'HAIR STONE :

Variety of quartz with inclusions of actinolite .

THOMSONITE :

Etym. dedicated to the chemist Th. Thomson

NaCa₂Al₅Si₅O₂₀.6H₂O

Physical and optical properties :

Colour : white, greenish, yellowish to yellow, reddish, pink, brownish, grey

Transparency : translucent to opaque

Lustre : vitreous

Hardness : 5 to 5.5

Density : 2.2 to 2.4

R.I. : 1.515 – 1.540 (±0.002)

Birefringence : 0.006 to 0.025

System : orthorhombic

THULITE :

Variety of compact and opaque zoisite of pink peach colour, found originally in Norway; the name derived from the legendary island of Thule .

Hardness : 6 to 6.5

THUMERSTEIN :

German Synonym for axinite .

THUMITE :

Synonym for axinite, etym. after Thum in Saxony .

THUMMERSTONE :

English Synonym for axinite .

THYRSITE :

Name given formerly to a kind of coral .

TIBET STONE :

English name for a stone composed of aventurine quartz and porphyre quartz showing colour variations

TIGER’S EYE :

Variety of quartz, formed from hawk’s eye through pseudomorphism of crocidolite in quartz, maintaining the original fibrous structure, the mostly banded light brownish golden to dark brownish golden colour is produced by iron; there is chatoyancy and a silky sheen also on fractures.

TINSTONE :

English name for cassiterite .

TITANATE DE STRONTIUM :

French name for strontium titanate ; correct appellation for the artificial product fabulite .

TITANE OXIDE :

Synonym for rutile .

TITANERZ :

German Synonym for rutile .

TITANE SILICEO-CALCAIRE :

Synonym for titanite .

TITAN-FAVAS :

Synonym for rutile, or anatase .

TITANIA :

Name given to a synthetic rutile .

TiO₂

Physical and optical properties : : identical to natural rutile

Colour : colourless, yellow, rarely in other colours

Dispersion : even higher than for the natural  rutile : 0.190

TITANIC SCHORL :

Synonym for rutile .

TITANITE : or sphene

Sometimes used wrongly as synonym for rutile .

Etym. From the Greek sphen = Keil in German

CaTiSiO₅  monoclinic

Physical and optical properties :

Colour : colourless, golden yellow, green, brown, pink, pink-red, black

Transparency : transparent to opaque

Lustre : adamantine, waxy

Hardness : 5 to 5.5

Density : 3.35 to 3.56

R.I. : 1.888 – 2.053 (±0.020)

Birefringence : 0.100 to 0.185

Dispersion : 0.019 to 0.051

Biaxial positive

System : monoclinic

SYNTHETIC TITANITE:

Name given to a kind of fabulite, or titania, both artificial products .

TITANOLIVINE : ( or SYNONYM : HUMITE )

Titaniferous Peridot .

TITANAMEORPHITE :

Variety of sphene .

TITANSCHORL :

Synonym of rutile .

TOAD'S-EYE TIN :

Reddish cassiterite with a concentric structure .

TODO MUNDO STONE :

Brazilian name for a dark green tourmaline with some yellowish or brownish nuances.

TOKAY LUX SAPPHIRE :

Prohibited Appellation for an obsidian variety from Hungary of brown-black colour .

TOMOSITE :

Variety of rhodonite .

TOPAZ :

Etym. : from the Sanskrit : Tapas = fire; yellow phosphorescent stone

Al₂SiO₄(OH, F)₂

Physical and optical properties :

Colours : colourless, yellow, golden yellow, orangy yellow, pink, golden pink, pink-red, brown-red, brown, blue, bluish-greenish

Transparency : transparent to translucent

Lustre : vitreous

Hardness : 8

R.I. : 1.619 (+0.014 –0.010) – 1.627 (+0.016 – 0.010)

Birefringence : 0.008 to 0.010

Dispersion : 0.008

Biaxial positive

Trichroism : yellow : distinct : citron yellow, honey yellow, golden yellow

                   blue : weak : pale blue, pink, colourless

                   red : strong : dark red, yellow, red-pink

Cleavage perfect basal

System : orthorhombic

Prohibited Appellation for a yellow quartz or citrine or for a yellow fluorite .

See equally Gemmological News concerning topaz.

(BOHEMIAN) TOPAZ :

Prohibited Appellation for a yellow quartz or citrine or for a yellow fluorite .

(BURNT) TOPAZ :

Yellow topaz that has been heated at low temperatures to give it a pink colour.

(CALIFORNIAN) TOPAZ:

Variety of pale blue topaz, found in California .

(CHRYSOLITE) TOPAZ :

Prohibited Appellation for a pale yellow or yellowish green topaz .

TOPAZE D'ECOSSE :

French name; Prohibited Appellation for a pale coloured smoky quartz .

TOPAZE ENFUMEE or FUMEE:

French name ; Prohibited Appellation for a smoky quartz .

TOPAZE D'ESPAGNE :

French name ; Prohibited Appellation for an amethyst turned yellow through heat-treatment .

TOPAZE DOREE :

French name ; Prohibited Appellation for a yellow citrine or for an amethyst that has been turned into a beautiful golden yellow colour through heat-treatment .

TOPAZE GOUTTE D’EAU :

French name given to a white topaz from Brazil .

TOPAZE INDIENNE :

French name given to a saffron yellow topaz from Sri Lanka .

Prohibited Appellation for a yellow corundum .

Prohibited Appellation for a citrine .

TOPAZE MADERE :

French Prohibited Appellation for an amethyst turned yellowish brown or brown-reddish through heat-treatment .

TOPAZE DU NEVADA :

French Prohibited Appellation for a smokey coloured obsidian .

TOPAZE OCCIDENTALE :

French Prohibited Appellation for a citrine .

TOPAZE ORIENTALE :

French Prohibited Appellation for a yellow sapphire  .

TOPAZE PALMYRE :

French Prohibited Appellation for a quartz turned yellow through heat-treatment .

TOPAZE-SAFRANITE :

French Prohibited Appellation for a citrine .

TOPAZE SALAMANCA :

French Prohibited Appellation for a citrine from Cordoba ( and not from Salamanca )

TOPAZE DE SAXE :

French Prohibited Appellation for a citrine .

SYNTHETIC TOPAZ :

Prohibited Appellation for a synthetic corundum or a spinel of yellow co1our .

TOPAZOLITE :

Variety of andradite garnet .

Colour : pale yellow, honey yellow, greenish yellow

Hardness : 6.5 to 7

Density : 3.80

R.I. : 1.89

TOPAZ QUARTZ :

Prohibited Appellation for a citrine .

TORRELITE :

Variety of jasper .

TORRENSITE :

A mixture of rhodonite and rhodochrosite .

TORTHOISE-SHELL :

Corneous plate forming the shield of the turtle.
Chemical composition  : 55% carbon, 20% oxygen, 16% nitrogen and 6% hydrogen.
Physical and optical properties:
- Colours : Translucent ; spotted, yellow, brown.
- Hardness : 2.5
- S.G. : 1.29
- R.I. : around 1.55
Occurrences :
Warmer Seas, Indonesia, India, Caribbean, Brazil.
Confusions :
- Bakelite (S.G. : 1.25 to 1.30 ; R.I. :1.65)
- Galalithe (S.G. : 1.33 ; R.I. : 1.55)
- " plaque écaillé" (French. Small pieces of tortoise-shell melted together under pressure. Analogous to pressed amber. Appears hazy observed in transparency).

TOSCANITE :

Quartz containing trachyte-andesite .

TOURMALINE :

Etym. from the Cingalese : turamail = precious brown stone

Complex Boro-Aluminium silicate

Na(Li, Al)₃Al₆. (OH)₁₊₃. (BO₃)3.Si₆O₁₈  albaite (lithium-tourmaline)

NaMg₃A1₆. (OH)₁₊₃. (BO₃)3.Si₆O₁₈    dravite (magnesium-tourmaline)

NaFe₃A1₆. (OH)₁₊₃. (BO₃)3.Si₆O₁₈     schorlite (iron-tourmaline)  

Physical and optical properties :

Colours : elbaite : colourless (achroite) and all colours : green in all nuances (verdelite),

                  pink to pink-red (rubellite), blue-green to dark blue (indigolite),

                  violet (siberite), peach colour (apyrite)

              dravite : brown

              schorlite or schorl : black

Transparency : transparent to opaque

Lustre : vitreous

Hardness : 7 to 7.5

Density : 3 to 3.25

R.I. : all : 1.624 (+0.015 –0.010 – 1.644 (+0.022 – 0.010)

       brown : 1.616 – 1.640 (+0.002)

       red : 1.630 (+0.009 – 0.002) – 1.662 (+0.006 – 0.004)

Birefringence : all : 0.020 (0.014-0.032)

               brown : 0.024 (0.023-0.026)

               red : 0.032 (0.027-0.032)

Dispersion : all : 0.009 – 0.011

            red : 0.014

Uniaxial negative

System : trigonal

See also les Gemmological News concerning the treatments of tourmaline.

(AFRICAN) TOURMALINE :

- Commercial name given to tourmalines of yellowish-green or bluish-green colour , not necessarily

   from Africa

- Name given to an emerald green tourmaline from South West Africa equally called tourmaline

   from Transvaal

(ALEXANDRITE) TOURMALINE :

See chameleonite .

CHROME-TOURMALINE :

Variety of tourmaline of non-gem quality of dark blue colour, showing a green fluorescence when  heated .

TOURMALINE MELON D’EAU :

French name ; variety of tourmaline with a centre coloured red or pink encircled by a green part .

TOURMALINE OEIL-DE-CHAT :

French name for cat’s eye tourmaline ; variety of tourmaline of different colours with chatoyant line when cut as a cabochon .

TOURMALINE from TRANSVAAL :

Synonym of African tourmaline  .

TOURMALINE QUARTZ :

Rock crystal with needles of tourmaline as inclusions .

TRAINITE :

Impure variety of banded variscite .

TRANSVAALITE :

Name given to a variety of green quartz looking like jade; colours : light to dark green, apple-green .

Etym. Named after its provenance: Transvaal ( according to Dana transvaalite is an hydrated oxide of Co )

TRANSVAAL JADE :

Commercial term designating a grossular garnet from South Africa.
Physical and optical properties :
Colours : green to light green with fine and compact grains .
Hardness : 7
S.G. : 3.45 to 3.50
R.I. : 1.72 to 1.73
Remarks :
This term designates equally :
A garnet of dark green nephrite colour from the mines of Buffelsfontein and Turffontein, South Africa.
A dark green andradite from South West Africa, equally called nephrite from Transvaal.

TRAUTWINITE :

Impure variety of uvarovite .

TRAVERSELLITE :

Variety of olive green diopside from Traversello in Piemont ( Italy ) .

TREMOLITE :

Etym. From the Tremolo valley in North Italy .

Variety belonging to the familly of the amphiboles ; present as a typical inclusion under the form of fine fibres in the emeralds from Sandawana, Zimbabwe.

Ca₂Mg₅(OH, F) ₂Si₈O₂₂

Physical and optical properties :

Colour : colourless, white, yellowish, grey, pale green, pink, brown

Lustre : vitreous

Hardness : 5 to 6

Density : 2.9 to 3.3

R.I. : average : 1.60 to 1.62

System : monoclinic

TRICHROITE :

Synonym for cordierite .

TRIP :

Variety of tourmaline of yellow colour and coming specially from Madagascar .

TRIPHANE :

Synonym for spodumene or equally used to designate a yellow spodumene .

TRIPLETINE :

Name given to a triplet, constituted of Beryl, imitating emerald .

TRIPLOCLASE :

Synonym for Thomsonite .

TRUE AMBER :

= real amber in English

Commercial term designating succinite .

TSILAISITE :

Variety of tourmaline from Tsilaisina in Madagascar, multi-coloured or ‘old’ pink .

TUMITE :

Synonym for axinite .

TURCHESIA :

Synonym for turquoise .

TURKIS :

German name for turquoise .

TURMALI :

Synonym for zircon .

TURQUOISE :

Etym. In antiquity and Middle ages known under the name Kallait ; from the Greek : Kallainos : sparkling blue and green

CuA1₆(PO₄)₄(OH)8. 4H₂0 

Physical and optical properties :

Colours : blue to blue-green, green

Transparency : Translucent to opaque

Lustre : vitreous

Hardness : 5 to 6

Density : 2.31 to 2.85

R.I. : 1.610 – 1.650 (average : ± 1.61)

Birefringence : 0.040

Biaxial positive

System :triclinique

(AMERICAN) TURQUOISE :

Turquoise from the South-Western states of the U.S.A, generally very pale blue o whitish green or bluish green ;

These turquoises are often impregnated to reinforce their colour, equally known under the name of Mexican turquoises .

(CALIFORNIAN) TURQUOISE :

Prohibited Appellation for a variscite .

Equally used to designate des natural turquoises from California or other South-Western states of the U.S.A.

(CHINESE) TURQUOISE :

Prohibited Appellation Term rarely used to designate an obsidian, steatite, calcite or quartz tinted blue .

Genuine turquoise from China .

(FOSSIL) TURQUOISE :

Prohibited Appellation for odontolite .

(MEXICAN) TURQUOISE :

See American turquoise .

(NEW MINE) TURQUOISE:

Prohibited Appellation for odontolite .

(OCCIDENTAL) TURQUOISE :

Prohibited Appellation for odontolite .

(REESE) TURQUOISE :

Prohibited Appellation for an imitation of turquoise of Reese fabrication .

TURQUOISE DE HAMBOURG :

French Prohibited Appellation for an imitation of turquoise .

TURQUOISE MATRIX :

Name for turquoise having inclusions of brown limonite or name for a mixture of turquoise and its (mostly brown or black) mother rock.

TURQUOISE VIENNOISE :

French Prohibited Appellation for an imitation of turquoise ; it is an artificial product made by  precipitation of aluminium phosphate coloured by an oleate of copper .

TUGTUPITE :

Etym. : named after Tugtup in Greenland

Na₈. C1₂(BeA1Si₄O₁₂)₂

Physical and optical properties :

Colours : pink or red, sometimes with whitish parts

Transparency : Transparent to opaque

Lustre : vitreous

Hardness :6 to 7

Density : 2.3 to 2.57

R.I. : 1.496 – 1.502

Birefringence : 0.006

Uniaxial positive

System tetragonal

TUXTLITE :

Etym. from Tuxtla in Mexico

Mineral composed of pyroxene, sodium and magnesium, and of which the principa1 constituent is mayaite .

TWIN STONE :

English Name for staurolite .

TYROLITE :

Synonym of lazulite .