EAGLE STONE :
Synonym of Aetite.

EAGLE EYE :
Variety of Quartz with blue chatoyancy

EARTH AMBER :
Term sometimes employed in England to differentiate mined Amber from marine amber.

EARTH STONE :
Synonym for Earth Amber.

ECAILLE:
French for tortoise-shell.

ECUME DE MER :
French for Meerschaum.

EDINITE :
Synonym for Prase.

EDISONITE :
Synonym for Rutile (Source : Dana).

EDELTOPAS :
German Term for a noble Topaz, term sometimes used in the past to differentiate true topaz from citrine topaz or quartz topaz (both prohibited appellations).

EDLER FELDSPATH :
German. Synonym for Labradorite.

EDLER GRANAT :
German Term for an almandine garnet.

EGERANE :
Or Egeranite.
Variety of green Idocrase found at Eger, in Hungary.

EGYPTIAN ONYX :
Prohibited Appellation for a variety of aragonite .

EILAT STONE:
Stone formed of a mixture of Malachite, Turquoise and Chrysocolla, found at Eilat (former Copper mines, already exploited in Pharaonic times) in Egypt. For others, it is a Chrysocolla , very strongly veined.
Physical and optical properties variable according to the percentages of each composing gemstone.

EISENANATES :
German Term for Hematite.

EISENGLANZ :
German Term for Oligiste or Hematite.

EISENKIESEL :
German Term for Pyrite or Marcassite.

EISENBLAU :
German Term for Vivianite, also employed to designate Lazulite.

EISENPHYLLIT :
German Term for Vivianite.

EKANITE :
Collector’s stone
Radioactive mineral of metamorphic origin.
CaTh(Si₄O₁₀)₂ or (Th,U)(Ca,Fe,Pb)₂(Si₄O₁₀)₂  
Physical and optical properties:
- Colours : light brownish green to dark yellowish-green, green, darkred.
- transparency : Transparent to translucent
- lustre : vitreous
- Hardness : 4.5
- S.G. : 3.08
- R.I. : 1.568 - 1.580 (birefr. : 0.012)
- uniaxial negative
- Crystal Crystal system : tetragonal
Occurrence :
Sri Lanka.
See also :
Ekanite, ein neuer metamikter Edelstein aus Ceylon, by E. Gübelin (ZDG n°40 ,  1962, page 14).

EKELBERGITE :
Synonym of Scapolite.

ELAEOLITE or ELAEOLITH :
Massive variety of Nepheline.
(Na,K)₈Al₈Si₈O₃₄  
Physical and optical properties:
- Colours : Green, red, brown, blue and grey.
- Hardness : 5 to 6
- S.G. : 2.55 to 2.65
- R.I. : 1.538 to 1.542
- Crystal system hexagonal

ELAINSPAT :
German term. Synonym for Scapolite.

ELBAITE :
Synonym for Rubellite.

EL DORADOÏTE :
Variety of blue quartz from El Dorado County, California.

ELECTRUM :
Ancient Latin Name used for Amber.

ELIE RUBY :
Or Ely Ruby.
Name wrongly given to a red Pyrope from Elie in Scotland.

ELIOTROPE :
See Heliotrope.

EMALDINE :
See Emildine.

EMERADA :
Commercial name given to a yellowish-green synthetic Spinel.

EMERALA :
Name given by the English to a green-yellow Peridot.

EMERALD :                                                                                                                          
etym; : from the Greek ‘smaragdos’.

Green chromiferous Beryl.
Al₂B₃[Si₆O₁₈]
Physical and optical properties:
- Colours : deep green to pale green. The green colour is caused by a replacement of at least 1,5% of the aluminium ions of the beryl by chromium ions.
- Transparency : transparent
- lustre : vitreous
- Hardness : 7.5 but the inclusions (in general very numerous)  can render the stone quite fragile.
- S.G. : 2.68 to 2.78
- R.I. : 1.571 - 1.597 (Birefr : -0.005 to –0.007)
- Uniaxial negative.
- Crystal system : hexagonal.
- Spectrum of chromium more or less clearly visible, + sometimes spectrum of iron in the blue.
- Fluorescence none in almost all the emeralds because they contain iron except in certain emeralds from Colombia where a reddish fluorescence will be perceptible under U.V..
Occurrences :
In chromiferous surroundings.
Emeralds from micas : Brazil ( +big producer in large quantities), Australia, Zambia, Austria, Urals, India, Pakistan, Nigeria, Mozambique, Madagascar,
Emeralds from calcareous sites : Colombia (+big producer in large quantities), Afghanistan,…
Confusions :
 Greenish aquamarine beryl. The essential difference is situated in the fact that the emerald owes its colour to chromium, and therefore possesses a chromium spectrum, whereby aquamarine owes its colour to iron and presents thus a typical iron spectrum.
Green tourmaline, jades, chrysoprase, peridot, tsavorite, apatite, demantoid garnet, grossular garnet, uvarovite garnet.
Inclusions :
Emeralds capture during their formation small pre-existing crystals (protogenetic inclusions) but undergo also fracturing.
These fractures may totally or partially undergo healing.
Emeralds from micas contain mica, tremolites-actinolites,… and healing fractures containing water and carbon rich solutions exempt of H₂O.
Emeralds from calcareous deposits will contain pyrite, calcite,… and healing fractures filled with solutions rich in carbon and alkaline salts.
Healing fractures are present in numbers in ALL emeralds, called " jardin " in French (actually a nice expression, invented by the French in the 19^th century, to sell more easily heavily included stones).
Three-phase inclusions are typical of Colombian occurrences and sometimes present in Afghanistan stones.
Treatments :
- Colouring : emeralds, being too pale, are sometimes treated with a colouring agent on their pavilion side.
- Oiling : almost ALL emeralds are – these days under pressure -  soaked in colourless natural oils.
- Tincture : emeralds that are too pale are sometimes soaked in a green coloured oil. This procedure may sometimes be discovered thanks to a red fluorescence and a typical absorption spectrum.
- Plastification (or filling with hardening materials) of fractures : same Crystal system as oiling but with synthetic resinous materials or des plastics sometimes coloured. This procedure fragilizes the stone, in time, and renders often impossible repolishing.
See also Gemmological News concerning treatments of Emeralds.

Synthetics :
Synthetic emeralds often (but NOT always) show a remarked red fluorescence.
Their exist two procedures de of fabrication of synthetic emeralds : the process of anhydrous dissolution (FLUX method) and the process of hydrothermal dissolution.
The most sure way of differentiating between synthetics and natural emeralds is the identification of the typical inclusions.
Imitations :
Green glasses, doublets and triplets (garnet - green glass, quartz- green glass -quartz, rock crystal- green paste -rock crystal, …), synthetic spinel.
Rock crystal, heated and than immediately thrown in a bucket of cold water (thermal shock – provoking cracking of the stone) and subsequently coloured imitates perfectly emeralds (this procedure is known from before Roman times).

See also Gemmological News concerning emerald.

(AFRICAN) EMERALD :
See emerald from Transvaal.
Remarks :
One also uses this term to designate a green fluorite (Prohibited appellation).

(CHATHAM) EMERALD :
Prohibited appellation for a synthetic emerald fabricated by the firm Chatham.

(SYNTHETIC) EMERALD OF CHATAM FABRICATION:
Synthetic emerald produced by the Chatham company, San Fransisco, U.S.A..
Physical and optical properties:
- Colours and Hardness relatively identical to those of natural emeralds.
- S.G. : 2.645 to 2.665.
- R.I. : 1.560 - 1.566 (Birefr : - 0.003 to 0.004).

(SYNTHETIC) EMERALD OF GILSON FABRICATION:
Synthetic emerald produced by the Gilson company,  Campagne-lez-Wardrecques, France.
Physical and optical properties:
- Colours and Hardness relatively identical to those of natural emeralds.
- S.G. : 2.601 to 2.668.
- R.I. : 1.559 - 1.566 (Birefr : - 0.003 to 0.004).
Commercialised under the French name of " Emeraude de Synthèse Gilson ".

(SYNTHETIC) EMERALD OF LECHLEITNER FABRICATION :
Synthetic emerald produced by the company of Lechleitner Idar-Oberstein, Germany.
Physical and optical properties:
- Colours and Hardness relatively identical to those of natural emeralds.
- S.G. : 2.66
- R.I. : 1.555 - 1.561 (Birefr : - 0.006)
- Less fluorescent under S.W.U.V. & L.W.U.V. then the former LINDE production.
Inclusions :
- Inclusions of Phenacite, crystals with a termination in the form of a lance.
- two-phase inclusions.

                                                                                                                         
(SYNTHETIC) EMERALD OF ZERFASS FABRICATION :
Usual appearance of synthetics of the flux-fusion process.
Physical and optical properties:
- Colours and Hardness relatively identical to those of natural emeralds.
- S.G. : 2.67
- R.I. : 1.560 - 1.564
- under U.V. : red

EMERALD FROM AUSTRALIA:                                                                                                     Syn. : Australian emerald.
Prohibited appellation for a pale green beryl.

EMERALD FROM BAHIA :
Prohibited appellation for a light coloured yellowish-green beryl from Bahia, Brazil.

EMERALD FROM BRAZIL :
Or Brazilian Emerald.
Physical and optical properties:
- Colours : Idem as for the other emeralds.
- Hardness : Idem.
- S.G. : 2.670 to 2.700.
- R.I. : 1.565 - 1.582 (Birefr. : - 0.004 to – 0.006).
Remarks :
Also a prohibited appellation for a green tourmaline.

EMERALD FROM BRIGHTON :
Prohibited appellation for a glass with a bottle green colour.

EMERALD FROM COLOMBIA :
Or Colombian emerald.
Physical and optical properties:
- Colours and Hardness idem as for the emeralds from other occurrences.
- S.G. : 2.690 to 2.710.
- R.I. : 1.569 to 1.584 (Birefr. : - 0.005 to 0.006)

EMERALD FROM CONGO :
Prohibited appellation for a Dioptase.

EMERALD FROM THE CAPE :
Prohibited appellation for a green Prehnite.

EMERALD FROM the HABACCHTAL :
Or Emerald from Austria.
Physical and optical properties:
- Colours and Hardness idem as for the other emeralds.
- S.G. : 2.72 to 2.75.
- R.I. : 1.584 - 1.591 (Birefr. : - 0.007)

EMERALD FROM TRANSVAAL :
The emeralds of South Africa (Gravelotte) have a poor colour, generally a tint of yellow or brown, caused by the  predominance of inclusions of plaques of mica.
Generally, the emeralds of Transvaal are not red under the Chelsea filter although coloured by chrome, as confirmed with the spectroscope.
Physical and optical properties:
- Colours and hardness identical with the usual average figures of natural emerald.
- S.G. : 2.720 to 2.8
- R.I. : 1.585 - 1.595 (Birefr. : - 0.007)
- Uniaxial negative

EMERALDINE :
Name given by the English to a Chalcedony tinted green by chromium oxides.

EMERALDITE :
Name given by the English to a green Zircon.

EMERALD MATRIX :
Prohibited appellation for a Fluorite.

EMERALITE :
Light green Tourmaline from Mesa Grande, California.

EMERAUDE :
French for emerald.        

EMERAUDE BATARDE :
French term. Prohibited appellation for a Peridot.               

EMERAUDE CUIVREE :
French term (copper-emerald). Prohibited appellation for a Dioptase.

EMERAUDE CULTIVEE :
French term. Prohibited appellation for a synthetic emerald.

EMERAUDE DE L'OURAL :
French term.
Physical and optical properties:
- Colours and Hardness identical to other emeralds.
- S.G. : 2.720 to 2.740
- R.I. : 1.579 - 1.588 (Birefr. : - 0.006 to – 0.007)
Remarks :
Also prohibited appellation for Demantoid Garnet.

EMERAUDE DE MEDINA :
French term. Prohibited appellation for a green coloured glass.

EMERAUDE DE NUIT :
French term for night emerald .

EMERAUDE ELECTRIQUE :
French term. Prohibited appellation for a green coloured glass.

EMERAUDE ESPAGNOLE :
French term. Prohibited appellation for a green coloured glass.

EMERAUDE FERRER :
French term. Prohibited appellation for a green coloured glass.

EMERAUDE GILSON :
French term. Prohibited appellation for a synthetic emerald made by Gilson.

EMERAUDE INDIENNE :
French for Indian emerald. Prohibited appellation for an – artificially ‘cracked’ (by thermal shock) and coloured -  Quartz.

EMERAUDE LITHIQUE :
French term.
Prohibited appellation for a green Spodumene (Hiddenite or Hydenite) containing a high proportion of lithium.

EMERAUDE ORIENTALE :
French term. Prohibited appellation for a green sapphire.

EMERAUDE SOUDEE :
French term. Appellation given to a triplet imitating emerald and composed generally of two parts of quartz or otherwise of two parts of synthetic spinel or also of two parts of beryl, assembled with in between a green glass, or a coloured paste or a green glue.