AHLAMAH :
Or Achlamah.
Ninth stone of the Rational of the High Priest of the Jews, generally accepted to have been an amethyst.

AIGUE MARINE : 
French name for Aquamarine.

AIMANT DE CEYLAN :
French name given to Tourmaline because it becomes electrically charged when heated (pyro-electricity).

AJKAÏTE :
Or Ajkite, variety of Amber.

AJOIT :
German name for Ajoite.

AJOÏTE : 
French name for Ajoite.

AJOITE :
Hydrous aluminium copper silicate
Generally found massive, only seldom crystals.
Collector’s gemstone
(K,Na)Cu₇AlSi₉O₂₄(OH)₆.3H₂O
Physical and optical properties :
- Colours : blue to bluish green
- Transparency : opaque
- Hardness : (higher than that of shattuckite or plancheite).
- P.S. : 2.9
- I.R. : 1.550 – 1.641 (birefr. : 0.091)
- biaxial positive
- Crystal : system triclinic
Occurrence :
Mineral discovered around 1958 at Ajo (Ajo Mine), Pima Co, Arizona, USA.

AKABAR :
Or Accarbaar. Name given to black Coral in regions of the Indian Ocean.

AKERITE :
Name given to a variety of blue Spinel.

AKORI :
A porous Coral from the coasts of western Africa, also Samoa.
Colour : red, blue, violet.
The name is also used to designate materials worked by the local people like glass, rock or nacre.

AKTINOLITH :
German name for Actinolite.

ALABASTER :
Etym. : from the Greek ‘alabastron’ designated a perfume vase without handle.
Massive Gypsum very finely grained (hydrated calcium sulphate)
CaSO₄.2H₂O
Physical and optical properties :
- Colours : white when pure ; coloured by oxides often of iron giving various colours : yellow, brown, red, orange, pink.
- transparency : translucent
- hardness : 2 to 2.5
- S.G. : 2.30 to 2.33
- R.I. : 1.520 - 1.530 (Birefr : +0.010)
- Crystal system : monoclinic
Treatments :
Since alabaster is very porous, it can easily be dyed any colour.
Occurrence :
Many places all over the world. The most known, and commercially exploited since antiquity are in Toscany, Italy.

ALBÂTRE :
French for Alabaster.

ALBITE :
Albite and orthose are the two stones composing Moonstone.
NaAlSi₃O₈
Physical and optical properties:
Colour : white, bluish, grey
Transparency : transparent to opaque
Lustre : vitreous
Hardness : 6 to 6.5
S.G. : 2.62 (2.6 – 2.7)
R.I. : 1.527 (+ 0.005) - n_z 1.538 (+ 0.004); n_y 1.532 (+0.003) (Birefr. : 0.007 to 0.011)
Biaxial negative or positive
Crystal system :Triclinic

ALEXANDRITE :
Etym. : named by the mineralogist A.E. Nordenskjöld in honour of the future Tsar Alexander II (1818 – 1881) because it was discovered on his birthday in 1831 at Takowaja, Ural. 
A variety of Chrysoberyl with colour change effect (in daylight : green – under incandescent light : red)
Alexandrites of gem quality showing the colour changing effect very distinctly are quite rare. 
BeAl₂O₄
Physical and optical properties :
- Colours : green in daylight, purplish red in artificial light.
- Transparent to translucent
- Lustre : vitreous
- Hardness : 8.5
- S.G. : 3.7
- R.I.: 1.744 - 1.755 (Birefr. : +0.009)
- Biaxial positive.
- Crystal system : Orthorhombic (prisms, twinning : twins or triplets).
- Strongly trichroic : intense red, yellow, green.
- Spectrum : absorption lines linked to chrome.
- Luminescence : pink.
- Cleavage : difficult.
- Fracture : irregular to conchoidal.
Occurrence :
Intrusive rocks with contact-metamorphism but mainly alluvial mineral.
Zimbabwe, India, Brazil, Sri Lanka, Russia (Ural), Zambia, Madagascar, Tanzania.
Imitations :
Glass, doublets, synthetic spinel, synthetic corundum.
Inclusions :
- Healing fractures identical to those present in corundum are sometimes present in alexandrite.
- Growth or twinning, in straight lines or sometimes angular.
- Cat’s eye alexandrites have very fine channels responsible for the effect. 
Confusions :
- Andalousite (S.G : 3.5 ; R.I.: 1.64)
- Tourmaline ( S.G. : 3.0 to 3.2 ; R.I. : 1.615 to 1.661)
- Cordierite (S.G. : 2.59 ; R.I. :1.535)
- Synthetic Corundum ( S.G. : 4 ; R.I. : 1.76 – 1.77 ; Birefr. : 0.008 ; curved zones ; gaze bubbles ; colour change violet, blue-green)
Synthetics :
Synthesis by the flux-melt process (identification : inclusions typical de for this type of  synthesis : melt-relics, black parasite crystals in the form of fine needles and platelets, a.o.)
Fabrication : USA, Japan, Russia, China.
See also :
- Chrysoberyl - Katzenauge- Alexandrite, by K. Schlossmacher (Z.D.G. n°40 , 1962, page 9).
- Alexandritevorkommen in Südrhodesien , by Hermann Bank (Z.D.G. n°47 , 1964, page 11).
- Alexandrite synthetisch (Z.D.G. n°50 de 1964, page 32).
- Alexandrite synthetisch aus der U.S.A. (Z.D.G. n°54 , 1964, page 32).
- Alexandrite von Brasilien (Z.D.G. n°54 , 1965, page 35).
- Mineralogische Untersuchung von Alexandrite von Novello Claims, Rhodesien, by H. Bank & M. Okrusch (Z.D.G. n°61 , 1967, page 33).
- Chrysoberyl - Alexandrite , hochlichtbrechend (Z.D.G. n°61 , 1967, page 54).
- Granat - Glas , Doublet-Imitation für Alexandrite (Z.D.G. n°64 , 1968, page 12).
- Synthèse d'alexandrites (T.E.C. n°241 , 1966, page 598).
- Alexandrite synthétique (T.E.C. n°254 , 1967, page 579).
- Spinelle artificiel, couleur Alexandrite (T.E.C. n°306 , 1972, page 31).

ALGERIAN ONYX :
Prohibited Appellation for a variety of calcareous alabaster .

ALGODONITE :
Collector’s stone.
Cu₆As
Physical and optical properties :
- Colour : white to steel-grey
- Lustre : metallic
- Hardness : 3.5 to 4
- S.G. : 8 to 8.39
- Crystal system : orthorhombic
Occurrence :
Algodones Mines, Coquimbo Province, Chile ; Michigan, U.S.A.

ALLANITE or ALLANITE EPIDOTE :
Belongs to the group of the epidotes
Colours : brown to black
Hardness : 5.5 to 6
See Epidote.
See also :
- Der Group des Epidots, by Verena Theisen (Z.D.G. n°48 , 1964, page 24 to 27).

ALMANDINE :
Etym. : name derived from ‘carbunculus alabandicus’ ; in Antiquity most stones of red
colour where called carbunculus (= ‘glowing charcoal’ ) ; in Roman times (noted down by a.o. Plinius) the city of Alabandes (about 50 km from the cities of Miletes and Ephesos in Asia Minor, now in Turkey) was known as a cutting and trade centre for gemstones, especially for a kind of red gemstones called ‘carbunculus alabandicus’.

Belongs to the group of the Garnets, and the most common of the group.
Neso-Silicate of aluminium and iron.
Fe₃Al₂[SiO₄]₃
Physical and optical properties :
- Colours : blood-red, brownish red, violet-red, dark red
- Transparency : transparent
- Lustre : vitreous
- Hardness : 7.5
- S.G. : 3.95 to 4.32
- R.I. : 1.78 to 1.81
- Anomalous birefringence under the polariscope.
- Crystal system : Cubic.
- Often an anomalous birefringence.
- Spectrum of iron (3 bands in the green + one in the orange and in the blue region.
- U.V. : no fluorescence.
- Fracture : conchoidal.
- Cleavage : imperfect (= no actual cleavage but a phenomenon of ‘parting’).
Occurrence :
found in rocks of regional-metamorphic origin, in volcanic rocks or sedimentary rocks.
Sri Lanka, India, Vietnam, Afghanistan, Brazil, Zambia, Madagascar Syria, Tanzania, Tyrol (Austria), Scotland, Sweden, Mozambique,…
Typical inclusions :
Syngenetic inclusions of zircon (with sometimes wing-like stress fractures).
Other inclusions : titanium under the form of oriented rutile needles following the host’s crystallographic directions (ex : symmetry quaternary axis), large crystals of red-brown to blackish rutile, also ilmenite (typical of almandine from Rajasthan, India);
further : monazite, hornblende (byssolite), augite, actinolite, tremolite, dendritic inclusions, several sulphur containing minerals like pyrite, pyrrholite, pentlandite, crystals of transparent  quartz, apatite.
Sometimes asterism.
Solid inclusions are numerous and very divers, liquid inclusions on the contrary are rare.
Imitations :
Glass, Synthetic corundum.
Confusion :
Spinel, brownish red tourmaline, idocrase, ruby, red and brown zircon.
Confusions :
- Ruby.
- Pyrope garnet (R.I. : 1,75).
- Spinel (R.I.: 1,71 to 1,72).
- Tourmaline and especially rubellite (anisotropic gemstone, R.I. : 1,62 to 1,64 + dichroism).
Prohibited Appelations :
- " Spinel-Almandine " P.A.
- " Almandite " P.A. for a synthetic spinel.
- " Amaryl " P.A. for a green synthetic corundum.

(ALMANDINE) RUBY :
Prohibited Appellation for a spinel, or for a red garnet

(ALMANDINE) SPINEL :
Prohibited Appellation for a violet to violet reddish spinel .

AMAZONITE :
Etym. : after the legendary tribe of the Amazons (a tribe exclusively composed of women); here the name was given by some early explorers of rain forest in the North of Brazil because there existed supposedly a tribe of women who gave this stone to the men of a neighbour tribe to ‘hire’ their services; this region was also given the same name of Amazon.

Synonym : microline.
Potassic tecto-alumino-silicate.
Group of the feldspaths (variety : microline). 
KAlSi₃O₈
Physical and optical properties :
- Colours : pale green, greyish green, blue-green more or less intense and sky-blue, pale to vivid turquoise-blue.
- Transparency : translucent to opaque
- Hardness : 6 to 6.5
- S.G. : 2.55 to 2.62
- R.I. : 1.522 - 1.530 (Birefr. : +0.008)
- Biaxial negative.
- Crystal system : Triclinic, prismatic.
- Cleavage : perfect, sometimes almost perpendicular.
- The forms of amazonite are those of orthose. Well crystallised, may present a nacreous cat’s eye effect due to it’s lamellar structure.
- Pleochroism : rare.
- Fluorescence : weak olive-green.
Occurrence :
Amazonite crystallised is rare. It is sometimes found a.o. at Broken Hill (Australia) and, cut, produces small stones that may resemble emerald.
Brazil, Madagascar, India, USA, Russia.
Inclusions :
Silvery reflections like sheets. Black dendritic inclusions are in some rare cases encountered.
Confusions :
All pale green to blue-green stones :
- jadeite jade (S.G. : 3.30 to 3.33 ; R.I. : 1.66 ; without silvery reflection).
- chrysoprase (S.G. : 2.65 ; R.I. : 1.53).
- green aventurine quartz (S.G. : 2.65 ; R.I. : 1.545 ; green platelets as inclusions ; reddish under Chelsea filter).
- turquoise (S.G. : 2.60 to 2.80 ; R.I. : 1.61 ; more opaque and without silvery reflection).
- chrysocolla (S.G. : 2 to 2.45 ; R.I. : 1.50 ; banded and/or veined, and without silvery reflection).
- variscite (S.G. : 2.4 to 2.6 ; R.I. : 1.56 ; without silvery reflection and sometimes spotted pale brown).
- howlite (S.G. : 2.30 to 6.30 ; R.I. : 1.50 ; anomalous under polariscope ; circular traces).
- serpentine (S.G. : 2.30 to 2.50 ; R.I. : 1.46 to 1.57 ; opaque ; more bluish pale green).
Imitations :
Glasses give only a very poor imitation of amazonite.
See also :
- Les feldspaths, by P. Van de Walle (TEC n°253 , 1967 page 516).

(AMAZONE) JADE :
Prohibited Appellation for Amazonite .

AMBER :
Synonym : Succin, succinite.
Etym. : until the 19^th century mainly the name Succin was used : the actual word amber (and ‘ambre’ in French) is supposed to derive from the Arab word ‘anbar’ , designating ‘perfumes to burn’ (incense and amber).

Mixture of various fossilized resins, from pine trees, formed in the Eocene period, about 50 million years ago, composed of succinic acid, volatile oils, and a certain amount of sulphur .
Product of the tree Pinus Succinifera.
Not to be confounded with grey amber, aromatic material, secreted by the cachalot whale.
Approx. : C₁₀H₁₆O (average : 78 % C, 10 % H, 11 % O and some S )
Aromatic hydro-carbonated chains.
Physical and optical properties :
- Colours : Transparent, translucent to almost opaque, yellow, yellow the colour of honey to brown, milky white, black, greenish, transparent to translucent, slightly oily aspect.
- Transparency ; transparent to translucent
- Hardness : 2 to 3
- S.G. : 1.04 to 1.10 (max. 1.30)
- R.I. : 1.539 to 1.545
- Amorphous.
- Anomalies under polariscope due to internal stress.
- Cleavage : none.
- Fracture : conchoidal , and internal fractures frequent.
- Fluorescence : bluish-white to yellow-green (Burmite : blue)
- Piezo-electricity (charged electronically when rubbed).
Occurrence :
Rumania, Sicily, Santo-Domingo, Myanmar, Libyan, Saint Dominique, Eurasia, Baltic, USA, … (almost everywhere except Africa & Antarctica).
Typical inclusions :
Bubbles (may render de stone opaque), insects, arachnids, etc.,… often fixed in an attitude of struggle. Normally, only the carapace of the insect remains. If the amber has penetrated the interior of the insect, it will be entirely mummified. 
Treatments :
Amber is whitish  when it has a myriad of air bubbles entrapped. To eliminate these, the stone is heated in Colza oil. This kind of heated stones present subsequently internal stress fractures resembling golden lotus flower leaves.
After some years, the stones become darkened and more reddish. To make them paler : treatment with chemicals.
Dying.
Treatment with heat and pressure.
Imitations :
- Small pieces and scrap (from cutting) of amber is pressed and melted together (presence of pronounced air bubbles).
- Doublets : amber/amber
- Copal : same origin (fossilised resin, but younger). Often dyed more yellow, hardness lower than that of true amber and it takes a lesser polish plus.
- Retinite : resin found in lignite.
- Ambrite : reddish material from New Zeeland.
- Yellow glasses and plastics, red bakelite.
!!! in these products, inclusions may be introduced to make them more convincing : bubbles, dead insects (fixed in the mass, showing no signs of struggle).
List of the confusions with their caracteristics :
- Copal (S.G.: 1,06 ; R.I. : 1,53).
- Tortoise-shell (S.G. : 1,29 ; R.I. : 1,55).
- Galalithe (S.G. : 1,33 ; R.I. : 1,54).
- Erinoïde (S.G. : 1,32 ; R.I. : 1,53) = imitation of tortoise-shell.
- Bakelite (S.G. : 1,28 ; R.I. : 1,64).
- Celluloid (S.G. : 1,38 to 1,42 ; R.I. : 1,49 to 1,50).
Synthetics :
- After the Second World War, the whole Baltic region, the most important occurrence of natural amber, was in the hands of the Russians, who did not export to the Occident.
In West-Germany, a formula was invented to produce synthetic amber (based on synthetic resin), that was very difficult to distinguish from it’s natural counterpart.
This new product was principally worked in factories in Bayern . (Technica n°88 de mars 1954)
- Extracts from the roots of certain trees, mixed with a little true amber.
- Artificial resins ( Recognition : often heavier than true amber).
Prohibited Appellation :
- " Mexican Amber " P.A. for Bakelite.
See also:
- L'ambre dans la mythologie grecque, (Technica n°109 , October 1955).
- Bernstein wieder im  Aufschwung, by Dr. H. Steinert (ZDG n°42 ,  1962, page 23).
- Neue Entdeckung von Bernstein in Lituanien (ZDG n°49 , 1964, page 35).
- Naturbernstein und Pressbernstein, by Prof. K. Schlossmacher (ZDG n°52 , 1965, page 10).
- Polybern, eine Berstein-Imitation (ZDG n°53, 1965, page 58).
- Bernstein entstand durch tertiäres Meeresklima, by Dr. Steinert (ZDG n°63, 1968, page 13).
- Légende de l'ambre (AFG n°9, page 12).
- Travail de l'ambre (TEC n°82 ,  1953, page 601).
- L'ambre synthétique (TEC n°88, 1954, page 151).
- Nordsee-Bernstein, by H. Jöns (ZDG 19, 1970, n°3/4, page 143).

(AMBER) OPAL :
Variety of opal having the colour of yellow amber

AMBLYGONITE :
Rare mineral and collector’s stone.
Basic lithium aluminium phosphate.
LiAl[(F,OH)PO4]
Physical and optical properties :
- Colours : colourless, pale yellow or in very light shades of purple, blue, grey, greenish, pink.
- Transparency : transparent
- Lustre : vitreous and on cleavage planes : pearly
- Hardness : 5.5 to 6
- S.G. : 3 to 3.11
- R.I. : n_x 1.591- n_z 1.613, n_y 1.605, can go up to 1.643 (Birefr. : -0.026 to –0.027)
- Biaxial negative.
- Crystal system :Triclinic.
- Cleavage : perfect.
- S.W.U.V. : sometimes weak pale greenish
Occurrence :
Brazil, North America, France, Australia, French Guyana.
Confusions :
Topaz.
See also :
- Some rare Materials, by W.F. Eppler (TJG volume 12 n°7, 1971, page 256).

AMBRE : 
French for amber.