ABALONE PEARL :
Natural pearl from the mollusc Haliotis (also called ear-shell). Mainly found as a blister pearl, but sometimes as a true pearl. It’s colours are : distinct green to pale green or pinkish.
Habitat : Pacific Ocean.

ABALONE PERLE :
German name for Abalone Pearl.

ABANDEROS :
Mexican name for Fire Opal.

ABRAXAS :
Mystical stone mentioned in the classical writings about the Goths and of which the nature is uncertain.

ACANTHICONE or ACANTICONE or ACANTICONITE :
Variety of Epidote (Variety found in Scandinavia).

ACANTHOÏDE :
Synonym for Diospide.

ACCARBAAR :
= Akabar.

ACENTELA :
Spanish name for Quartz in general and Rock Crystal in particular.

ACHAT :
German name for Agate.

ACHATES :
Ancient name for Agate, Quartz.

ACHAT PRUHOVANY :
Czech name for Agate.

ACHIRITE :
Variety of Dioptase (Variety found in Siberia).

ACHMATITE :
Variety of Epidote (Variety found in the Urals).

ACHROITE :
Variety of colourless Tourmaline.
Imitations :
Pink tourmalines can be decoloured by heat-treatment.

ACORITE :
Synonym for Zircon.

ACQUAMARINE :
Italian name for Aquamarine.

ACROIT :
German name for Achroite.

ACROITA :
Spanish name for Achroite.

ACROITE :
Italian name for Achroite.

ACRUSITE :
Synonym for Cerusite.

ACRYLIC :
= acrylic plastics or plexiglass

ACRYLIQUE :
French for acrylic.

ACTINOLITE :
Of the Amphibole Family, principal constituent of nephrite.
Synonym : Actinote.

Etym. : from the Greek ‘aktis’ or ‘aktinos’ meaning ‘ray’ or ‘spoke’ from a wheel (because of its fibro-radiated aspect)
Ca₂(Mg, Fe)₅[Si₄O₁₁]₂(OH)₂
Physical and optical properties :
- Colours : green, bottle green, olive green or blackish green, with whitish-greenish spots, greenish yellow, colourless to white, often with fibre-radiated aspect.
- Transparency : Transparent to translucent
- lustre : vitreous
- Hardness : 5.5 to 6
- Density : 3.05
- R.I.: 1.614 (+ 0.019) - 1.641 (+0.012) (Birefr. : 0.020 to 0.025).
- Biaxial positive (Bank) or biaxial negative (Webster).
- Trichroic : green – greenish yellow- very pale yellow. Or : bluish green- pale green – yellowish green.
- Crystal system : monoclinic.
- Perfect prismatic cleavage.
Occurrence :
Metamorphic mineral, found frequently in carbonated rocks (dolomite).
Afghanistan and eastern Africa (ex : Uganda), but also in the U.S.A. (Ontario) and Greenland.
Litterature:
- Grüner transparanter Aktinolith , Hermann Bank. (Z.D.G. 1969, N°1, page 1)
- Zu der Gitterkonstanten von " Edelaktinolith " by H. Bank and B. Nuber (Z.D.G 19, 1970, N°2, page 55)
- Aus der Gemmologischen Prüfungspraxis (Z.D.G. 19, 1970, N°2, page 80)

ACTINOLITE-ASBESTOS :
Asbestos variety of Actinolite.

ACTINOTE :
Synonym for Actinolite.
French name for Actinolite.

ACTYNOLIN :
Synonym for Actinolite.

ACTYNOLITE :
Original spelling of Actinolite.

ADAMANT :
Old synonym for diamond ( to others also syn. for corundum). From the ancient Greek adamas.

ADAMANTINE SPAR :
English name for a silky brown sapphire.

ADAMAS :
Name given in Antiquity by the Greek to the diamond.

ADAMITE :
Commercial name given by manufacturers to artificial corundum used as an abrasive.

ADELAIDE RUBY :
Prohibited Appellation for an almandine garnet from Australia (found near Adelaide) or for a pyrope, the colour of blood, from South Africa.

ADINOL :
A silicified Porphyry or diabase.

ADULAIRE :
French name for Adularia.

ADULARIA : 
Colourless to milky, transparent to translucent, gem-variety of orthoclase feldspar.

Showing the phenomenon of adularescence : a milky blue sheen.
See Feldspath, and synonym Moonstone.
Etymology : from Mount Adula in the region of St. Gothard.
See also :
- Une Pierre Oubliée : l'Adulaire par H. Mornard (T.E.C. n°188 , 1962, page 121).
- La Pierre de Lune par F. Duyk (T.E.C. n°231, 1965 , page 695).
- Les Feldspaths par P. Van de Walle (T.E.C. n°253 , 1967, page 513).

AEROHYDRE :
French name. Particular type of Agate, also called water-agate.

AEROÏDES :
American name sometimes given to pale beryl, the colour of a pale blue sky.

AERINITE :
Blue ‘Outremer’ (= coloration pigment), a product of pyroxenetic alteration and mixed with Lapis-Lazuli.

AETITES :
Synonym of " Eagle stone".
Ancient name designating stones discovered in the nests of eagles, some of these aetites are small geodes with a mobile interior. Occurrence : in the neighbourhood of Trévoux and Ales (France).

AFRICITA :
Spanish name designating a black Tourmaline.

AFRICAN EMERALD :
Prohibited Appellation for a green fluorite.

AFRICAN JADE :
Prohibited Appellation for a massive green grossular garnet.

AFRICAN PEARL :

Natural Pearl from the Iles Bazaruto, near Zanzibar (Africa).
Synonym of Bazaruto Pearl. (Source : Robert M. Shipley)

AGALMATOÏDE :
Synonym for Agalmatolite.

AGALMATOLITE :
Synonym : Agalmatoïde.
Designates generally a talc-like stone, Steatite or Pagodite (pyrophyllite or pinite (= muscovite variety of mica)).
Physical and optical properties :
- Colours : pale green, veined with grey and white, compact stone with greasy lustre, sometimes yellowish or brownish.
- Hardness : 2 to 3
- S.G. : 2.75 to 2.90

AGAPHITE :
Synonym : Agapite.
Turquoise of beautiful blue colour known in the trade under the name of oriental Turquoise (Ancient appellation).
To others, the name designates a vitreous variety of Persian Turquoise.

AGATE :
Of the Group of micro-crystalline Quartz. One of the varieties of chalcedony with zones differently coloured constituted of successive layers of chalcedony ± thick, straight or irregular. The alternating layers of the agate are due to the varying rhythm of growth of the stone. Each layer of the agate presents a different colour.
SiO2 (Silicon dioxide)
Physical and optical properties :
- Colours : colour of the constituting chalcedonies : white, bluish grey, grey-green, yellow-brown, brown, brown-red.
- Transparency : translucent to opaque
- Hardness: 6.5 to 7
- S.G. : 2.60 to 2.65
- R.I. : 1.535 - 1.539 (-0.005) (birefr. : 0.004 to 0.006)
- Uniaxial positive or negative.
- Crystal system : trigonal
- Cleavage : none.
- Fluorescence variable within the layers, sometimes strong, yellow, bluish white.
Typical inclusions :
- Dendrites of manganese, and inclusions of goethite, chlorite,…
These inclusions when suitably disposed in a stone correctly cut may resemble plants, mountains,…
Treatments :
The layers of chalcedony are porous and are therefore frequently dyed in any wanted colour.
Occurrence :
Forms at lower temperatures in cavities in fine grained ( basaltic) volcanic rocks.Various places all over the world. The most important commercially are : the northern part of Uruguay and in the Rio Grande do Sul, Brazil.
Imitations :

TYPES OF AGATES :
- Water agate (synonym : Aerohydre or Enhydritic agate : agate polished in such a way as to make apparent the water imprisoned in the stone. It is in fact a closed geode.
- Amethyste agate : agate with purple to dark violet colour, finely zoned with pearly grey colours.
- Dendritic agate (synonym : landscape/scenic agate or tree agate) : also called Mocha stone (name of a city in the Arabic peninsula where it hence came from). Agate with red, brown or black dendritic inclusions, due to the presence of iron and/or manganese oxides. Note : is actually no agate but chalcedony because it is not banded.
- Brecciated agate : broken pieces of agate held together by a natural siliceous cement.
- Iceland agate : Prohibited Appellation for a grey obsidian.
- Fire agate : agate from Mexico where the spherules are covered with a kind of iridescence making it look like opal.
- Fortification agate : agate where the fine layers resemble fortifications.
- Iris agate : agate comprising des interference colours caused by very fine colourless layers almost transparent.
- Jasper agate : agate comprising parts of jasper.
- Moss agate : = no agate but a variety of milky chalcedony with moss-like inclusions of green or rusty brown colour due to chlorite inclusions.
- Black agate : Prohibited Appellation for jet.
- Opal agate : Opal banded alternatively with layers of opal and of chalcedony.
- Nicolo agate or nicolo : agate with two or more black or very dark brown layers alternated with one or more white or bluish grey layers, the whole cut as a cabochon. Note : nicolo = name used to designate antique, mainly Roman, mostly three layered, intaglio cut stones.
- Eye agate : agate composed of several layers of different colours, cut as a cabochon making them look like eyes.
- Cat’s eye Agate : this time the cut brings out the eye pattern.
- Landscape agate : here the inclusions and the cutting makes it look like a landscape. (see dendritic agate)
- Blood or blood red agate : name given by the Americans to pink or salmon coloured agates coming from the mine in Utah.
See also :
- Künstlich gefärbte Achat-Lagensteine, by K.  Schlossmacher (Z.D.G. n°30 , 1959, page 20).
- Die Entstehung der Achate, Teil I, by K. Schlossmacher (Z.D.G. n°32 , 1960 page 16).
- Die Entstehung der Achate, Teil II, by K. Schlossmacher (Z.D.G. n°33 , 1960 page 11).
- Elektronenmikroskopische Untersuchungen zur Fasertextur des Achates, by Jürgen Pense (Z.D.G. n°38 , 1961 page 12).
- Achate, neuer Provenienz aus Kalifornien (Z.D.G. n°44 , 1963 page 25).
- Doublet Moss-Achat (Z.D.G. n°49 , 1964 page 33).
- Feuer-Achat (Z.D.G. n°57 , 1966 page 49).
- Achate von Turtle Moutains, Kalifornien (Z.D.G. n°57 , 1966 page 50).
- Description d'une agate avec une réflexion assortie, par Roger Callois (A.F.G. n°9, page 10).
- Les agates et l'imagination, par Roger Callois (A.F.G. n°16, page 9).
- L'origine du nom Agate, par E. Sarofin (A.F.G. n°18, page 11).
- Origine de l'Agate, by K. Schlossmacher (T.E.C. n°41 , 1950, page 305).
- Origine de l'Agate 2ème Partie, by K. Schlossmacher (T.E.C. n°43 , 1950, page 433).
- L'origine du nom Agate, par E. Sarofin (T.E.C. n°296 , 1971, page 127).

(AGATE) OPAL :
Variety of opal banded like agate or presenting alternating layers of opal and layers of chalcedony .

AGNI-MANI :
Synonym : pearl of fire or Billitonite (= a tektite).

AGSTEIN :
German name for Jet.

AGUSTITE :
Synonym for Apatite.