(AMERICAN) JADE :
Equally called " Wyoming jade ".
Nephrite from Wyoming, U.S.A..
Equally Prohibited Appellation for a Californite .

(AMERICAN) RUBY :
Prohibited Appellation for a red garnet .

AMETHYST :
Etym. : from the Greek ‘a – methustes’ meaning ‘ not drunk ‘ .
Belongs to the Quartz Group.
SiO₂
Physical and optical properties :
- Colours : reddish violet or bluish violet.
- Transparency : translucent to transparent
- Lustre : vitreous
- Hardness : 7
- S.G. : 2.63 to 2.65
- R.I. : 1.544 - 1.553 ( Birefr: + 0.009)
- Uniaxial positive
- Dichroism : distinct : violet, violet-grey.
- Crystal system :Trigonal.
- Fracture : conchoidal.
- Cleavage : none.
- Weak greenish fluorescence (sometimes).
- Becomes pink, or reddish under the Chelsea filter.
The distribution of colour seems linked to the polysynthetic twinning. Colour is due to a colour centre.
Typical inclusions :
healing fractures with an aspect like zebra skin, linked to the twinning phenomena, sometimes filled with a liquid. Crystals of goethite, of cacoxenite and hematite in form of irregular reddish fibres  … .
When these inclusions are present in yellow (citrine) quartz, we can almost be sure to be in the presence of heated amethyst. 
Healing fractures, in general, are quite frequent, in the form of very fine veils, composed of liquid inclusions, not oriented.
Treatments :
- heat treatment of amethysts allows the " transformation " into another gemstone :  citrine (if the yellow stone is dichroic, it is a true citrine).
- If the amethyst is heated to higher temperatures, it becomes milky and makes a very good imitation for moonstone.
The heated stones can take their initial appearance by irradiation.
- It occurs that fractures are filled with polymer substances to make them less visible.
Occurrence :
Madagascar, Brazil, France, India, Mexico, USA.
Often found in geodes, in pegmatite rocks.
Imitations :
- Triplets of green quartz and violet quartz.
- Violet glasses & violet synthetic corundum (bubbles, curved growth striae)
- Pieces of amethyst encompassed in glass.
Confusions :
- Morganite (S.G. : 2.80; R.I. : 1.59 to 1.60; Birefr. : + 0.008).
- Kunzite (S.G. : 3.18 ; R.I. : 1.67 ; Birefr. : + 0.015).
- Violet spinel (Isotropic ; S.G. : 3.60, R.I. : 1.717 ; octahedral inclusions).
- Violet sapphire (S.G. : 3.99 ; R.I. : 1.765 ).
- Violet almandine garnet (Isotropic ; S.G. : 3.9 to 4.1 ; I.R. : 1.775 to 1.830).
- Fluorite (Isotropic ; S.G. : 3.18 ; R.I. : 1.43).
- Tourmaline (S.G. : 3.05 ; R.I. : 1.62 to 1.64 ).
- Synthetic spinel and synthetic corundum.
Synthics :
Synthetic (hydrothermal) amethyst. Mostly very clean stones & strongly dichroic.
Prohibitted appellations :
- " Lithic amethyst " P.A. for kunzite.
- " Amethyst-Quartz " P.A. for cordierite.
See also :
- Amethyst aus Brasilien (ZDG n°41, 1962, page 24).
- Spectographische Studien am Amethyst, by Rudolf Thurm (ZDG n°48, 1964, page 34).
- Die Farbe von Amethyst (ZDG n°59, 1967, page 7).
- Eine neue Amethystimitation, by Herman Bank (ZDG n°63, 1968, page 16).
- Optisches über die Farbe des Amethysts, par Siegfried Rösch (ZDG Sonderheft n°3, 1969).
- Amethyst von Bahia, Brasilien, by Hermann Bank (ZDG Sonderheft n°3, 1969).
- L'améthyste du Massif du Mont-Blanc (AFG n°26, page 13).
- Amethyst aus Wyloo Station in Australien (ZDG 18, n°4 , 1969, page 185).
- L'améthyste et le bombardement atomique expérimental (TEC n°86 , 1954, page 41).
- Du neuf en matière de gemmes vertes (améthyste chauffée) (TEC n°105 , 1955, page 399).
- De la couleur et de la stabilité de la couleur dans l'améthyste (TEC n°236 , 1966, page 152).
- Les améthystes étaient devenues jaunes après deux ans (TEC n°268 , 1968, page 705).
- Une exploitation primitive : les gisements d'améthyste de Brejinho (Bahia - Brésil), by J. Cassedanne (AFG n° 31, page 14).
- Une exploitation primitive : les gisements d'améthyste de Brejinho (Bahia - Brésil) suite, by J. Cassedanne (AFG n° 32, page 7).

(AMETHYST) QUARTZ :
Term generally used to designate massif amethyst, often veined with bands of white opaque Quartz.

AMETHYSTE :
French for amethyst.

AMPHIBOLE :
Family comprising several varieties : actinolite, tremolite and nephrite.

AMYGDALOID :
Term designating agates having covered the interior of cavities formed in lava, thanks to successive layers of microcrystalline silica.

ANALCIME :
Synonym : Analcite.
Collector’s stone.
NaAlSi₂O₆.H₂O
Tecto-silicate.
Physical and optical properties :
- Colour :, white or grey, pinkish, yellowish, reddish.
- Transparency : transparent to almost  opaque.
- Lustre : vitreous
- Hardness : 5 to 5.5
- S.G. :2.44 to 2.50
- R.I. : when cubic, average : 1.487 ; 1.479 (+ 0.014) – 1.480 ( + 0.014) (Birefr. : 0.001 to 0.004)
- Crystal system : triclinic, but can be cubic
- Sometimes slightly anomalous under polariscope (Colourless analcime from Australia).
Occurrence :
- Copper Falls, Michigan, U.S.A.
- Val de Fassa, north of Italy.
- Cyclope Isles east of Sicily.
- Australia
- Saint Hilare, Canada
- Isles of Kerguelen in the Indian Ocean
- Scotland
- Czech Republic
- Japan

ANATASE :
Titanium Oxide.
Ti O₂
One of the 3 stones, together with Rutile and Brookite, that are oxides of titanium.
Very rare gemstone, collector’s stone and rarely cut.
Physical and optical properties :
- Colours : blue indigo, blue-green, black, brown yellowish, reddish to greenish (pale lilac, grey, rarely almost colourless.
- Transparency : transparent, translucent to almost opaque.
- Lustre : adamantine to resinous
- Hardness : 5.5 to 6
- S.G. : 3.82 to 3.96
- RI.. : 2.493 - 2.554 (Birefr. : - 0.046 to – 0.067)
- Uniaxial negative.
- Crystal system : tetragonal.
- Dichroism distinct : dark blue or orange / pale blue or yellowish.
Occurrence :
U.S.A., Brazil, Switzerland, France. Italy.

ANDALUSITE :
Etym. : from Andalusia, region in Spain, where it was discovered for the first time.
Silicate of aluminium.
Al₂SiO₅
Physical and optical properties : (+ See Spectrum  brown Andalousite / green Andalousite)
- Colours : brown, yellow with nuance of green (Fe & Mn), pink, rarely red.
It’s colour is caused by the presence of iron and of manganese. The latter can sometimes be replaced by aluminium (up to 3,5%), augmenting the refractive index.
- Transparency : transparent
- Lustre : vitreous
- Hardness : 7.5
- S.G. : 3.12 to 3.18
- R.I. : 1.634 (+ 0.008 / - 0.007) - 1.643 ( + 0.006 / - 0.003) (Birefr. : -0.007 to 0.013)
- Crystal system : Orthorhombic (thick columnar crystals, fibrous aggregates).
- Dichroism distinct : yellow green, brownish green.
- Cleavage : good, parallel with crystal faces.
- Spectrum : 3 to 5 absorption lines are visible in the yellow-green in the beautiful green specimens from Brazil.
- Fluorescence : weak greenish, yellow-green.
Confusions :
- Tourmaline (if one does not take care to take measurements of physical properties correctly).
- Apatite green (S.G. : 3 ; R.I. : 1.64 ; weak birefringence).
- Cordierite (S.G. : 2.59 ; R.I. : 1.535 ; dichroism : intense brownish, light blue and blue-grey, "
- Obsidian (S.G. : 2.4 to 2.6 ; R.I. : 1.50 ; isotropic)
- Smoky Quartz ( S.G. : 3.65 ; R.I. : 1.54)
- Disthene (S.G. : 3.6 to 3.7 ; R.I. : 1.72 ; cleavage at right angles).
Occurrence :
Sri Lanka, France, Spain, Russia, Madagascar and Brazil specially for gemstone quality.
In pegmatite or in certain granites, they can be associated with garnets.
Andalousite is a typical mineral of contact metamorphism of clay sediments.
Imitations :
- Synthetic spinel (S.G. : 3.65 ; R.I. : 1.50 ; isotropic with phantom images under the polariscope)
- Synthetic corundum (S.G. : 4 ; R.I. : 1.76 to 1.77 ; curved colour zone and growth striae)
See also :
- Die Kreuzsteine Staurolite und Andalousite, by Verena Theisen (ZDG n°43 , 1963, page 21).

ANDRADITE :
Etym. : named in honour of the Brazilian mineralogist José Bonifacio de Andrada e Silva (1763 – 1838).
Belongs to the group of the garnets.
Ca₃Fe₂(SiO₄)₃ 
The black variety is called Melanite, the yellow one Topazolite and the one with a brilliant lustre is the demantoid (garnet with a lustre like diamond, hence the name, and very rare).
Physical and optical properties :
- Colour : green (demantoid), black (melanite), yellow brown (topazolite).
-Transparency : Transparent to opaque.
- Lustre : vitreous (adamantine for demantoid).
- Hardness : 6.5.
- S.G. : 3.82 to 3.85 (3.90 for melanite).
- R.I. : 1.880 to 1.895.
- Crystal system : Cubic.
- Pink to red under the Chelsea filter for demantoid.
Occurrence :
- Italy and France for Melanite.
- Russia, Dem. Rep. of Congo for demantoid.
- Italy and Switzerland for Topazolite.
- Arizona for andradite yellowish-green, opaque (cut as cabochon).
Inclusions :
Fibres of chrysotile (typical for Russian demantoid).

ANGLESITE :
Collector’s stone.
Etym. : named after the location Pary's Mine on the Island of Anglesey in Wales, U.K.
Belongs to the Barite group.
A lead sulphate.
Pb[SO₄]
Physical and optical properties :
- Colours : colourless to white, often tinted grey; sometimes with some yellow tint, green or blue.
- Transparency : transparent.
- Lustre : adamantine to waxy or vitreous
- Hardness : 2.75 to 3
- S.G. : 6.30 to 6.39
- R.I. : 1.877 - 1,894 (Birefr. : 0.017).
- Biaxial positive.
- Crystal system : Orthorhombic.
- Pale yellow fluorescence under S.W.U.V.
Occurrence :
U.S.A. and Morocco.

ANHYDRITE :
Collector’s stone.
Etym. : name taken from the Greek ‘a – hydro’ meaning without water.
Ca[SO₄]
Physical and optical properties:
- Colours : colourless, white, bluish-white.
- Transparency : Transparent to translucent.
- Lustre : vitreous
- Hardness : 3 to 3.5
- S.G. : 2.899 to 2.985
- R.I. : 1.571 - 1.614 (Birefr. + 0.040 to 0.043)
- Biaxial positive.
- Crystal system : monoclinic or orthorhombic.

ANTIGORITE :
One of the three varieties of fibrous green Serpentine , can be chatoyant when cut as cabochon.
Physical and optical properties:
- Hardness : 2.5 to 4
- S.G. : 2.40 to 2.58
Prohibited Appellations :
- the English term " Bowenite " forbidden appellation when wanting to designate Antigorite.

ANTOPHYLLITE :
Silicate of manganese containing iron and calcium.
Not used as a gemstone.

ANYOLITE :
Massive green variety of Zoisite with inclusions of ruby.
Physical and optical properties:
- Hardness : 6
- S.G. : 3.3
- R.I. : 1.7
- Crystal system : Orthorhombic.
Occurrence :
Matabu Mountains, Tanzania

APATITE :
Etym. : name derived from the Greek ‘apatao’ meaning ‘to fool’ ; named as such by the German geologist- mineralogist Abraham Gottlob Werner (1750–1817) because of its very variegated crystal habit due to which it can easily be confounded with other minerals like for example beryl.
Phosphate of calcium.
Ca₅(F, Cl, OH)[PO₄]₃
Physical and optical properties:
- Colours : colourless, pink, yellow, green, blue, violet. Its colour depends on the content of calcium, manganese, rare earth elements, … (are therefore allochromatic gemstones).
- Transparency : Transparent.
- Lustre : vitreous
- Hardness : 5
- S.G. : 3.17 to 3.23
- R.I. : 1.632 - 1.651 (- 0.002 to 0.006)
- Uniaxial negative.
- Crystal system : hexagonal .These crystals are more or less elongated, terminated with a simple base or by pyramids or occur in lamellar structure.
- Pleochroism : faint yellow, green for green apatite. Strong blue, colourless for blue apatite.
- Cleavage perpendicular to Optical Axis.
- Fluorescence : variable (yellow apatite : pinkish-lilac / blue apatite : dark brilliant violet blue to sky blue / green apatite : mustard-green / purple apatite : greenish yellow under L.W.U.V. and pale purplish under S.W.U.V.).
- Spectrum : yellow apatite is a stone that shows a typical  rare earth elements spectrum (spectrum of des didymium : 2 groups of fine lines, one in the yellow region and one in the green, see Spectrum).
Green apatite has no distinct spectrum.
Blue apatite presents absorption lines in the green and in the blue.
Occurrence :
Is mainly found in secondary deposits and in metamorphic rocks.
- Mexico (yellow apatite )
- Spain and India (green apatite)
- Sri Lanka (blue apatite)
- Saxony in Germany, Portugal, USA (violet to blue apatite),
- Brazil (all colours),
- Pakistan / Afghanistan (all colours).
- Norway (green-blue apatite = Moroxite).
Confusions :
- Topaze (S.G. : 3.53 to 3.56 ; R.I. : 1.61 to 1.64 ; (healing) fractures, two-phase inclusions; growth traces).
- Danburite (S.G. : 3 to 3.56 ; R.I. : 1.63 to 1.636 ; didymium spectrum).
- Tourmaline (S.G.: 3.05 ; R.I. : 1.62 to 1.64 ; (healing)-fractures).
- Scheelite (S.G.: 5.9 to 6.1 ; R.I. : 1.91 to 1.93 ; spectrum of didymium).
- Phenacite (S.G.: 2.95 to 3 ; R.I. : 1.65 to 1.66).
- Celestine (S.G.: 3.97 to 4 ; R.I. : 1.62 to 1.63).
- Orthose (S.G.: 2.56 ; R.I. : 1.527 ; less brilliance).
- Citrine, Amethyst (S.G. : 2.65 ; R.I. : 1.545).
- Spinel (S.G. : 3.60 ; R.I. : 1.717).
- Sapphire violet (S.G. : 3.99 ; R.I. : 1.765 ; although the optical characteristics are very  different, the internal inclusions, (healing)-fractures and flags of de droplets, resemble those of apatite.
- Aqua-marine (S.G. : 2.69 ; R.I. : 1.575 ; strongly dichroic ; bluish under Chelsea filter).
- Zircon green and blue (S.G. : 4.69 ; R.I. : 1.95 ; blue zircon becomes slightly reddish under the Chelsea filter).
Imitations :
- Glass (S.G. : 2.2 to 5 ; I.R. : 1.45 to 1.65 ; bubbles and traces of melting).
Treatments :
- most blue apatite is obtained by heat-treatment of blue-green to greenish stones.
See also:
- Die beiden “Täuscher” : Apatite Phenakit, by Verena Theisen (ZDG n°44 , 1963, page 11).
- Apatit Katzenauge (ZDG n°54 , 1965, page 35).
- Mineraologisch-gemmologische Untersuchungen an Apatiten von Edelsteinqualität aus dem Casaccia-Tal, Tessin, by E. Gübelin (ZDG n°61 , 1967, page 75).
- Aus der gemmologischen Prüfungspraxis, by H. Bank (ZDG 18, n°4 , 1969, page 189).
- Aus der gemmologischen Prüfungspraxis, Folge, by H. Bank (ZDG 19, n°3/4, 1970, page 182).

APHRIZITE :
Term used for designating a black Tourmaline of Norway.

APOPHYLLITE :
Synonym for fluorapophyllite.
Name for a group of minerals comprising : a.o. fluorapophyllite, hydroxyapophyllite, natroapophyllite.
Very rarely cut ; a collector’s stone.
KCa[F|(Si₄O₁₈)2]₈H₂O
Physical and optical properties :
- Colour : colourless, sometimes yellowish, green or pink .
- Transparency : Transparent to translucent.
- Lustre : vitreous and nacreous
- Hardness : 4.0 to 5
- S.G. : 2.3 to 2.4
- R.I. : 1.535 - 1.537 (Birefr. : 0.001 to 0.002)
- Uniaxial positive or negative.
- Crystal system : tetragonal

APYRITE :
Ancient appellation for a Tourmaline , the colour of pale rose-wood.

AQUAGEM :
Prohibited Appellation for a  synthetic spinel of aqua-marine colour.

AQUAMARINE:
Etym. : from the Latin ‘aqua marina’ ; a term (translated from an earlier publication in Italian) first used in Occidental literature by Anselmius Boetius de Boot in his treatise on stones ‘Gemmarum et Lapidum Historia’ first published in 1609.
Belongs to the Beryl Group .
Silicate of aluminium and beryllium.
Al₂Be₃[Si₆O₁₈]
Physical and optical properties: (+ See Spectrum).
- Colours : pure blue to greenish blue. The colour is due to the  presence of iron.
- Transparency : transparent to translucent.
- Lustre : vitreous
- Hardness : 7.5 to 8.
- S.G. : 2.67 to 2.71
- R.I. : 1.577 to 1.583 (birefr. : - 0.006).
- Uniaxial negative.
- Dichroism : medium.
- Crystal system : hexagonal (hexagonal elongated prisms).
- Cleavage : imperfect.
- Fracture : irregular to conchoidal.
- Spectroscope : absorption band in the violet more fine in the blue.
- Fluorescence : none.
- Sustained green under Chelsea filter.
Occurrence :
Brazil (Bahia : pale blue to blue-green / Espirito Santo : transparent as water and colourless / Minas Gerais : dark tones), Madagascar (Tongafeno : sustained blue), Russia (Ural : clear blue to dark blue), India, Viet-Nam, Nepal, Afghanistan, Pakistan, Nigeria, Namibia, Mozambique, Zambia, in intrusive rocks Zimbabwe (dark blue, a little hazy).
Inclusions :
Small channels on which the light sometimes reflects . When there are many, cat’s eye effect, exceptionally six rayed star.
Fine liquid inclusions + mica, Quartz, feldspath, garnet, tourmaline and iron containing crystal also with titanium content.
Imitations :
Glass coloured by cobalt, also synthetic spinel and doublets (=>intens red under Chelsea filter >< against green for true aquamarine).
Treatments :
Almost all of the aquamarines from Brazil are heat-treated to improve the blue colour (the yellow component disappears from the greenish stones).
Treatment by irradiation has been abandoned because these stones lose their colour on exposure to sunlight.
Treatment by cobalt irradiation, on the contrary, has been widely used on beryls to produce maxixe-type aquamarines, of intense blue colour. This type of stones give a pinkish reaction under the Chelsea filter.
Synthics :
Possible but until recently too costly to be commercialised (note : recently : production for commercial purposes from Russia). 
Confusions :
- Quartz blue green (S.G. : 2.65 ; R.I. : 1.54 ; vitreous lustre).
- Tourmaline (S.G. : 3.10 ; R.I. : 1.62 Birefr. : 0,018 ; strong dichroism).
- Topaz blue (S.G. : 3.53 ; R.I. : 1.61 – 1.62 Birefr. : 0,008 ; fort dichroism).
- Euclase (S.G. : 3.10 ; R.I. : 1.65 – 1.67 Birefr. : 0,018).
- Sapphire light coloured from Sri Lanka (S.G. : 4 ; R.I. : 1.76 – 1.77 Birefr. : 0.008 ; weak dichroism ; wing-shaped healing fractures).
- Zircon (S.G. : 4.20 ; R.I. : 1.88 – 1.99 Birefr. : 0.059 ; weak dichroism ; artificial coloration by thermal treatment).
- Glass (S.G. : variable ; R.I. : 1.48 to 1.70 ; amorphous; bubbles).
- Synthetic spinel (S.G. : 3.66 ; R.I. : 1.73 ; Mono. ; anomalous reaction under polariscope, red under Chelsea filter).
- Synthetic corundum (S.G.: 3.53 ; R.I. : 1.76 – 1.77 Birefr : 0.008 ; bubbles ; colour zoning).
- YAG blue (S.G. : 4.65 ; R.I. : 1.83 ; Mono. ; Dispersion 0.028).
=> => => Prohibited Appellations :
- Brazilian Aquamarine : P.A. for a blue Topaz.
- Chrysolithe Aquamarine P.A. for Chrysolithe.
- Oriental Aquamarine P.A. for a Sapphire.
- Aquamarine from Thailand P.A. for a Zircon turned blue by heating.

AQUAMARINE EMERALD :
Prohibited Appellation for a triplet imitating Aquamarine and made up of two parts of colourless (or very pale) beryl glued together with a piece of email glass of green colour in between.

ARAGONITE :
Only cut for collector’s.
Carbonate of calcium.
CaCO3.
Also as micro-crystals the main component in the composition of pearls. These micro-crystals are disposed radiating in concentric spheres, linked together by an organic material. 
Physical and optical properties:
- Colours : colourless, yellowish, ivory-coloured, beige zoned with graduated brown shades, sky-blue zoned with pale blue.
- transparency : transparent to translucent.
- lustre : vitreous.
- Hardness :3.5 to 4.
- S.G. : 2.94.
- R.I. : n_x 1.530 - n_z 1.685 ; n_y 1.680 (Birefr. : 0.156).
- Biaxial negative.
- Crystal system : orthorhombic.
- Aragonite has the same chemical composition as calcite.
- Cleavage none.
Occurrence :
U.S.A. (Arizona), Germany, Spain, Italy, Greece (Laurion), France (Gard).
Confusions :
The yellow banded material of Karibib (South-west Africa) sold as aragonite is in reality stalagmitic calcite.

ARIZONA SPINEL :
Prohibited Appellation for a garnet.

ASPARAGUS STONE :
Variety of apatite from Spain of asparagus-green colour .

ASTERIATED RUBY :
Synonym for star ruby.
These rubies have two sets of rutile needles, crossing at 60° and 120°, and are cut as cabochons to obtain the effect of a moving and brilliant star.
(See also Ruby).

ASTERITE :
Erroneous Appellation for cat’s eye Quartz.
Also used as synonym for an asteriated sapphire.

ASTRIDIE :
French for Astridite.

ASTRIDITE :
A Rock composed of chromo-jadeite, picotite, Quartz, opal and limonite.
This stone is dedicated to Queen Astrid and found in  New-Guinea.

AUGELITE :
Phosphate of aluminium hydrated.
Al₂(PO)₄(OH)₃
Rare, collector’s stone.
Physical and optical properties:
- Colours :, colourless, pale yellow, pale pink .
- Transparency : transparent.
- Lustre : vitreous
- Hardness : 4.5 to 5
- S.G. : 2.5 to 2.7
- R.I. : 1.574 - 1.588 (Birefr. : 0.014)
- Biaxial positive.
- Crystal system : monoclinic
Occurrence :
U.S.A., Bolivia.
See also :
Augelit (ZDG 19 de 1970, n°3/4, page 175).

AUGITE :
Variety of black to brownish Pyroxene.

AUSTRALIAN OPAL :
Opal coming from Australia , but generally designating its variety of black opal

AVENTURINE or AVENTURINE QUARTZ:
Etym. : a type of glass discovered at Murano (Venice) ‘by chance’ ‘a ventura’ around 1700 gave the name to the similar looking stone.
Crypto-crystalline variety belonging to the Quartz Group.
Containing platelets of fuchsite-mica or hematite, giving a metallic iridescent effect (called aventurescence).
SiO2 dioxyde of silicium .
Physical and optical properties:
- Colours : green (fuchsite-mica) or golden brown (iron-mica) shiny with metallic iridescence, rarely bluish .
- Transparency : Translucent to opaque.
- Lustre : vitreous.
- Hardness : 7.
- S.G. : 2.64 to 2.69 .
- R.I. : 1.544 - 1.553 (Birefr. : +0.009)
- Crystal system : trigonal.
- No pleochroism.
- U.V. : Reddish.
Occurrence :
Found in veins in schists or in alluvial deposits.
Madras and Mysore (India) (green), Jaipur (India) (bluish), Brazil (green), Tomsk in central Asia (green), Zlatoust (ural) (green), Bavaria (Germany) (green), Almeria (Spain) (red-brown), Nantes (France) (brown).
Confusions :
Jade.
Imitations :
Aventurine glass : with triangular or hexagonal platelets of copper dispersed at random.

AVENTURINE FELDSPAR :
Synonym for sunstone.

AVENTURINE FELDSPATH :
French Synomym for sunstone .

AXINITE :
Collector’s stone.
Complex borosilicate of aluminium, iron, manganese and calcium.
Ca₂(Fe, Mg, Mn) Al₂(OH.BO₃.Si₄O₁₂)
Cyclo-silicate.
Physical and optical properties:
- Colours : yellow-orange to brown, brown-violet, brown-yellow, pale violet, honey-yellowish with bluish tint, pink, orange, very rarely blue.
- Transparency : transparent to translucent.
- Lustre : vitreous
- Hardness : 6.5 to 7.
- S.G. : 3.26 to 3.30.
- R.I. : 1.674 t- 1.704 ( -0.011)
- Crystal system : triclinic (tabular crystals).
- very strong dichroism : olive green, blue with violet tint, brown.
- Spectrum : three absorption bands in the blue region and the blue-green.
- Cleavage : none to distinct.
- Fracture : conchoidal.
- U.V. : reaction almost absent.
- Spectrum : lines at 512nm, 492nm and 4660nm (See Spectrum).
The structure of axinite is close to tourmaline.
Occurrence :
In Alpine clefts  in France (Bourg d'Oisans, Isère) and Switserland (Scopi), California (Baja), Brazil (Minas Gerais), U.S.A. (Franklin Furnace, New-Jersey), Great-Britain (Cornwall), Tasmania.
Inclusions :
Frequent liquid feathers.
Confusions :
- Quartz smoky .
- Tourmaline ( S.G. : 3.1 ; R.I. : 1.62 to 1.64)
- Andalousite (S.G. : 3.15 ; R.I. : 1.63 to 1.64).
- Fosterite (S.G. : 3.27 ; R.I. : 1.635 to 1.670).
- Epidote brown (S.G. : 3.35 to 3.50 ; R.I. : 1.74 to 1.78 ; absorption spectrum : strong band around 455 nm in the blue ; rarely cut since too dark).
See also:
Axinite aus Mexico ( ZDG n°56,  1966, page 33).

AZURITE :
Synonym : Chessylite.
Hydrated carbonate of copper.
 Cu₃[(OH)₂|(CO₃)₂]
Physical and optical properties:
- Colours : azure blue, blue ‘outremer’ or dark blue, blue and green.
- Transparency : translucent to opaque.
- Lustre : vitreous.
- Hardness : 3.5 to 4.
- S.G. : 3.77 to 3.89.
- R.I. : 1.730 - 1.838 (+0.08 to 0.11).
- Biaxial positive.
- Crystal system : monoclinic (short columnar crystals, compact aggregates).
- Cleavage : sometimes.
- Pleochroism : distinct light blue, dark blue.
- Spectrum : an absorption line in the green-blue, difficult to see.
- Fluorescence : none.
Occurrence:
France (Chessy), Chile, Mexico, Namibia, Morocco, Arizona, Siberia, … often in copper deposits or near by.
Confusions :
Lapis-lazuli, lazulite, haüyne, sodalite.
Inclusions :
Azurite and malachite are sometimes found harmoniously intermixed(by syn-genesis) and form a mass of azurite-malachite with a very beautiful aspect.

AZURITE - MALACHITE :
Compact mass with alternating colours of Malachite and Azurite  (vivid green and intense blue).