5 Achroite 9 Cancrinite 6-8 Feldspar 5 Larimar 8 Peristerite 3 Spinel
5 Actinolite 7 Carnelian 4 Fibrolite 5 Lazulite 8 Petalite 4 Spodumene
8 Adularia (moonstone) 1 Cassiterite 9 Fluorite (fluorspar) 8 Leucite 6 Pezzottaite 3 Staurolite
8 Afghanite 2 Cathaystone 4 Forsterite 3 Leuco garnet (grossular) 4 Phenakite 6 Stichtite (chrysotile)
7 Agate 3 Cat's eye (crysoberyl) 2 Gahnite 8 Limori stone 5 Phosphophyllite 1 Strontium titanate
8 Albite 5 Celestine 3 Gahnospinel 8 Magnesite 9 Plastic 5 Sugilite
3 Alexandrite 2 Cerussite 2-3 Garnet 4 Malachite 8 Pollucite 8 Sunstone
3 Almandine 7 Chalcedony 1 GGG 3 Malaya 7 Prase 7 Swiss lapis (jasper)
8 Amazonite 6 Charoite 8 Glass 3 Mali garnet 7 Prasiolite 3 Taaffeite
7 Amber 4 Chiastolite 8 Goldstone 3 Mandarin (spessartite) 5 Prehnite 3 Tanzanite
5 Amblygonite 4 Chloromelanite (jadeite) 6 Goshenite (beryl) 1 Marcasite (see pyrite) 1 Pyrite 8 Tektite
7 Amethyst 5 Chondrodite 5 Grandidierite 8 Maw-sit-sit 3 Pyrope 8 Thomsonite
8 Ammolite 3 Chrysoberyl 3 Grossular 6 Maxixe 7 Quartz 3 Thulite
7 Ametrine 8 Chrysocolla 9 Hackmanite 2 Melanite (andradite) 9 Reindeer stone 7 Tiger's eye
1 Anatase 7 Chrysoprase 6 Hambergite 5 Melinophane 3 Rhodizite-londonite 2 Titanite
4 Andalusite 6 Chrysotile 9 Haüyne 8 Metajade (limori stone) 6 Rhodochrosite 5 Topaz
6 Andesine 7 Citrine 7 Hawk's eye 7 Milarite 3 Rhodolite 2 Topazolite (andradite)
2 Andradite 4 Clinohumite 6 Heliodor 1 Moissanite 3 Rhodonite 6 Tortoiseshell
2 Anglesite 7 Copal 7 Heliotrope 8 Moldavite (tektite) 7 Rock crystal 5 Tourmaline
6 Antigorite 6-9 Coral 1 Hematite / hematine 5 Montebrasite 5 Rubellite 5 Tremolite
3 Anyolite 6 Cordierite 5 Hemimorphite 8 Moonstone 2 Ruby 3 Triphylite
4 Apatite 2 Corundum 6 Herderite 6 Morganite 1 Rutile 3 Tsavorite
7 Apophyllite 4 Cross stone (chiastolite) 3 Hessonite 7 Morion (smoky quartz) 8 Sanidine 8 Tufa (aragonite)
7 Aqua aura (rock crystal) 3 Cross stone (staurolite) 5 Hexagonite 8 Mother-of-pearl 2 Sapphire 9 Tugtupite
6 Aquamarine 1 Cubic zirconia 4 Hiddenite 7 Mtorolite 3 Sapphirine 5 Turquoise
8 Aragonite 1 Cuprite 5 Howlite 3 Musgravite 7 Sard / sardonyx 9 Ulexit
7-8 Aventurine quartz/feldspar 4 Danburite 3 Hydrogrossular 9 Natrolite 8 Saussurite 8 Unakite
4 Axinite 4 Datolite 9 Hydrophane (opal) 7 Nepheline 7 Scapolite 2 Uvarovite
3 Azurite 2 Demantoid 4 Hypersthene 5 Nephrite 2 Scheelite 6 Variscite
4 Barite 1 Diamond 9 Iceland spar (calcite) 8 Obsidian 5 Schorl 5 Verdelite (tourmaline)
3 Benitoite 3 Diaspore 3 Idocrase 5 Odontolite (see turquoise) 7 Sea opal (mother-of-pearl) 6 Verdite
6 Beryl 4 Diopside 5 Indicolite 4 Olivine 6 Serpentine 3 Vesuvianite
6 Beryllonite 4 Dioptase 6 Iolite 7 Onyx 3 Shattuckite 4 Violane (diopside)
6 Bixbite 3 Disthene 7 Ivory / vegetal ivory 8 Onyx marble (aragonite) 8 Shell 6 Water "sapphire" (iolite)
1 Blende 9 Dolomite 4-5 Jade (jadeite / nephrite) 9 Opal 4 Sillimanite 6 Wernerite
7 Bloodstone (heliotrope) 5 Dravite 7 Jasper 9 Opalite (opal imitation) 4 Sinhalite 3 Willemite
5 Bluespar 4 Dumortierite 8 Javaite (tektite) 8 Orthoclase 9 Slocum stone 6 Williamsite
6 Bowenite 8 Eilat stone (chrysocolla) 4 Jeremejewite 2 Padparadscha 5 Smaragdite (actinolite) 1 Wulfenite
5 Brazilianite 5 Ekanite 4 Jet 2 Painite 5 Smithsonite 5 Wyoming jade (nephrite)
4 Bronzite 6 Emerald 4 Kornerupine 5 Pargasite 9 Sodalite 2 YAG
7 Burmite (amber) 4 Enstatite 4 Kunzite 8 Pearl 6 Spectrolite (labradorite) 1 Zincite
6 Bytownite 3 Epidote 3 Kyanite 5 Pectolite 3 Spessartite 2 Zircon
9 Calcite 4 Euclase 6 Labradorite 3 Periclase 1 Sphalerite 3 Zoisite
3 Californite (vesuvianite) 5 Eudialite 8 Lapis lazuli 4 Peridot 2 Sphene 3 Zultanite
COPYRIGHT: Hervé Nicolas Lazzarelli 2002-2008 http://www.gembluechart.com
Bluechart or gem blue chart is a new and up-to-date gem identification
chart. In the world of gem Identification Instruments and
Accessories ,it appears as a "perfect" gemological tool, It
contains the distinctive features of some 200 gemstones.Anybody
who needs a quick, accurate and definitive gemstone identification:
Ideal for the Gemology student, professional gemmologists,
gem dealers, jewellers, and gem collectors.Most complete and
practical gem property chart ever published... Practical
orientation with focus on really distinctive characteristics. Common
and less common traps are emphasized.In this gem reference
chart the colours are widely used to quickly and clearly point
out distinctive features such as polariscope reactions, wide
ranges, doubling, phenomena, treatments, common and uncommon
stones, blinking, etc.Special care has been taken to show
colours as close as possible to natural/enhanced colours.
Special emphasis on features that help distinguish between
natural , treated gems, synthetic and imitation / fake gemstones.
Classification is based on refractive index; at the end of
the chart you will also find a classification based on specific
gravity.In addition, an alphabetical index leads to individual
gem characteristics.Handy metal wire ring-bound booklet. It
contains 10 double pages and has a format that fits easily
everywhere.Common gem denomination.Common gem denomination
with a clear distinction between GROUP, SPECIES, SUBSPECIES,
and VARIETIES is used.
Common and rare phenomena are indicated in distinctive colours.Colour
range is shown as close as possible to natural/enhanced colours.
Common and less common colours are included.Colour range is
shown as close as possible to natural/enhanced colours. Common
and less common colours are included. Refractive index, birefringence
and doubling.Classification by refractive index with a clear
reading of the range. The wide ranges (rhodochrosite, smithsonite,
unakite, etc.) are shown in red.birefringence, birefringence
range and blinking are clearly indicated. Possible doubling
is shown in red.Crystal system, optic character and sign...Quick
colour separation of polariscope reactions and crystal systems.
Crystal system, optic character and sign.Specific gravity...Classification
by specific gravity with a clear reading of the range.At the
end of the chart you will find a table listing gems in order
of their specific gravity.Hardness range... Distinctive characteristics
/ Common inclusionsThe right-hand side pages show many tricks
and tips in addition to typical features such as visual characteristics,
typical inclusions, distinctive spectrum, filter reactions,
...Focus is on distinctive characteristics. Common and less
common traps are pointed out. Jewelery tool, ... / ...differences
between natural, synthetic, treated and imitated gemstones
are explained as clearly as possible.A practical index with
241 entrees completes the chart and allows for quick reference
check.Hervé Nicolas Lazzarelli.Bluechart es una nueva
y actualizada carta de la identificacion de la gema. Contiene
las caracteristicas distintivas de unas 200 piedras preciosas
. Cualquiera que necesita una identificacion rapida, exacta
y definitiva de la piedra preciosa: Ideal para los estudiantes
de Gemmology, los gemmologists profesionales, los distribuidores
de la gema, los joyeros, y los colectores de la gema. La carta
mas completa y mas practica de la referencia de la identificacion
de la gema publicada siempre Orientacion practica con el foco
en caracteristicas realmente distintivas Se acentuan el campo
comun y las trampas menos comunes Los colores se utilizan
extensamente precisan a rapidamente y claramente caracteristicas
distintivas tales como reacciones del polariscopio, amplias
gamas, doblando, piedras de los fenomenos, de los tratamientos,
comunes e infrecuentes, centelleo, etc. El cuidado especial
se ha llevado los colores de la demostracion tan cerca como
sea posible a los colores de natural/enhanced enfasis especial
en las piedras preciosas de las caracteristicas que ayudan
a distinguir entre natural , tratado, sinteticas y de imitacion.
La clasificacion se basa en el �ndice de refraccion
; en el extremo de la carta usted tambien encontrar una clasificacion
basada en gravedad especifica. Ademes, un indice alfabatico
conduce a las caracteresticas individuales de la gema El alambre
de metal practico anillo-limita el librete. Contiene 10 paginas
dobles y tiene un formato que quepa facilmente por todas partes
Bluechart est un nouveau et jour diagramme d'identification
de gemme. Il contient les dispositifs distinctifs d'environ
200 pierres gemmes . Quiconque qui a besoin d'une identification
rapide, precise et definitive de pierre gemme: Ideal pour
des etudiants de Gemmology, des gemmologists professionnels,
des marchands de gemme, des bijoutiers, et des collecteurs
de gemme. Le diagramme de reference d'identification de gemme
le plus complet et le plus pratique ... Orientation pratique
avec caracteristiques vraiment distinctives et les pieges
moins communs sont soulignes Des couleurs sont largement utilisee...
rapidement et clairement les dispositifs distinctifs tels
que des reactions de polariscope, , doubling, pierres de phenomenes,
de traitements, communes et rares, ... Soin special
a ete pris aux couleurs d'exposition aussi etroitement que
possible aux couleurs de natural/enhanced Consideration particuliere
sur les pierres gemmes de dispositifs qui aident a distinguer
naturel , traitee, synthetiques et d'imitation. La classification
est basee sur l'indice de refraction ; l'extremite du
diagramme vous trouverez egalement une classification base
sur la densite. En outre, un index alphabetique mene a
differentes caracteristiques de gemme Le fil maniable en m�tal
anneau-bondissent le livret. Bluechart ist ein
neues und aktuelles Edelsteinkennzeichnung Diagramm. Es enth�lt
die unterscheidenden Eigenschaften von ca. 200 Edelsteinen
. Jedes, das eine schnelle, genaue und endg�ltige Edelsteinkennzeichnung
ben�tigt: Ideal f�r Gemmology Kursteilnehmer,
professionelle gemmologists, Edelsteinh�ndler, Juweliere
und Edelsteinsammler. Komplettestes und praktischstes Edelsteinkennzeichnung
Bezugsdiagramm �berhaupt ver�ffentlicht Praktische
Lagebestimmung mit Fokus auf wirklich unterscheidenden Eigenschaften
Common und weniger allgemeine Fallen werden hervorgehoben
Farben werden allgemein zu schnell und unterstreichen offenbar
unterscheidende Eigenschaften wie Polariskopreaktionen, die
breiten Strecken verwendet und verdoppeln, der Behandlungen,
allgemeiner und seltener die Steine der Ph�nomene,
und blinken, usw.. Besondere Sorgfalt ist zu den Erscheinenfarben
so nahe angewendet worden, wie m�glich zu den natural/enhanced
Farben Besondere Betonung auf den Eigenschaften, die helfen,
zwischen nat�rlichem zu unterscheiden, behandelt, synthetischen
und nachgemachten Edelsteinen. Klassifikation basiert auf
Brechungsindex ; am Ende des Diagramms finden Sie auch eine
Klassifikation basiert auf spezifischem Gewicht. Zus�tzlich
f�hrt ein alphabetischer Index zu einzelne Edelsteineigenschaften
Handlicher Metalldraht Ring-springen Brosch�re. Er
enth�lt 10 doppelte Seiten und hat ein Format, das
leicht �berall pa�t Bluechart PYRITE,
HEMATITE, CUPRITE, MOISSANITE, RUTILE, DIAMOND, IRRADIATED
DIAMOND, SYNTHETIC DIAMOND, STRONTIUM TITANATE, SPHALERITE, WULFENITE,
CUBIC ZIRCONIA, G.G.G, CASSITERITE, SCHEELITE, SPHENE, ANDRADITE,
DEMANTOID, UVAROVITE, YAG, GAHNITE, CERUSSITE, CATHAYSTONE,
ZIRCON, HIGH TYPE ZIRCON, MEDIUM TYPE ZIRCON, LOW TYPE ZIRCON,
CORUNDUM, YELLOW, BLUE, ORANGE, GREEN SAPPHIRE, PADPARADSCHA,
DIFFUSED PADPARADSCHA, RUBY, HEAT-TREATED CORUNDUM, HEAT-TREATED
SAPPHIRE, HEAT-TREATED RUBY, DIFFUSED CORUNDUM, DIFFUSED SAPPHIRE,
SYNTHETIC FLAME FUSION,
SYNTHETIC FLUX, SYNTHETIC HYDROTHERMAL, SYNTHETIC SAPPHIRE,
SYNTHETIC RUBY, SYNTHETIC CORUNDUM, VERNEUIL RUBY, VERNEUIL
SAPPHIRE, FLAME FUSION RUBY, FLAME FUSION CORUNDUM, HYDROTHERMAL
RUBY, GARNET, SPESSARTITE, ( SPESSARTINE ), MALAYA, COLOUR
- CHANGE, COLOR CHANGE,ALMANDINE, RHODOLITE, PYROPE, GROSSULAR,
GROSSULARITE, HESSONITE, TSAVORITE AND IMITATION,GAHNOSPINEL,
BENITOITE, SHATTUCKITE, CHRYSOBERYL, CAT'S EYE, ALEXANDRITE,
SYNTHETIC CHRYSOBERYL, SYNTHETIC CAT'S EYE, SYNTHETIC ALEXANDRITE,
STAUROLITE, EPIDOTE, AZURITE , HYDROGROSSULAR GARNET, SPINEL, SYNTHETIC
SPINEL, FLUX SPINEL, TAAFFEITE, RHODONITE, IDOCRASE, KYANITE,
WILLEMITE, ZOISITE, TANZANITE, THULITE, DUMORTIERITE, AXINITE,
DIOPSIDE, SINHALITE, KORNERUPINE, ENSTATITE, BRONZITE,
HYPERSTHENE, JADEITE, JADE, IMPERIAL JADEITE, DYED JADEITE,
LAVENDER JADEITE, SILLIMANITE, SPODUMENE, KUNZITE, HIDDENITE,
JET, MALACHITE, DIOPTASE, PHENAKITE, EUCLASE, PERIDOT,
SYNTHETIC FORSTERITE, BARITE, APATITE, ANDALUSITE, CHIASTOLITE,
DANBURITE, DATOLITE, TOURMALINE, IRRADIATED TOURMALINE, HEAT-TREATED
TOURMALINE, ACROITE, PARAIBA , RUBELLITE, DRAVITE, SCHORL,
INDICOLITE, CHROME TOURMALINE, SMITHSONITE, ACTINOLITE, ACTINOLITE
CAT'S EYE, NEPHRITE, TOPAZ, TOPAZ IMPERIAL, PREHNITE,
LAZULITE, TURQUOISE, IMPREGNATED TURQUOISE, RECONSTRUCTED
TURQUOISE, SYNTHETIC TURQUOISE, SUGILITE, MONTEBRASITE, AMBLYGONITE,
BRAZILIANITE, PECTOLITE, LARIMAR, EKANITE, PHOSPHOPHYLLITE,
HOWLITE, VERDITE, RHODOCHROSITE, VARISCITE, BERYL, AQUAMARINE,
BIXBITE, MORGANITE, HELIODOR, GOLDEN BERYL, EMERALD, FLUX
EMERALD, HYDROTHERMAL EMERALD, SYNTHETIC EMERALD, FRACTURE-FILLED
EMERALD, FRACTURE FILLING, FELDSPAR, LABRADORITE, CORAL
CONCHIOLIN, IMITATION CORAL, SERPENTINE, BOWENITH, BERYLLONITE,
TORTOISESHELL, CHAROITE, QUARTZ CRYSTALLINE, ROCK CRYSTAL,
AQUA AURA, AMETHYST, CITRINE, AMETRINE, PRASIOLITE, LEMON
ROSE SMOKY QUARTZ, HYDROTHERMAL QUARTZ, QUARTZ MICROCRYSTALLINE,
AVENTURINE QUARTZ, PRASE, QUARTZ CAT'S - EYE, TIGER'S - EYE,
HAWK'S - EYE, IOLITE, IVORY, VEGETAL IVORY, TAGUA, AMBER,
COPAL, AMBROID, SCAPOLITE, QUARTZ CHALCEDONY, CHRYSOPRASE,
MTOROLITE, CARNELIAN, SARD, HELIOTROPE, ONYX, SARDONYX, AGATE,
FIRE AGATE, IRIS AGATE, MOSS AGATE, DENDRITIC AGATE, JASPER,
APOPHYLLITE, SHELL, MOTHER-OF-PEARL, AMMOLITE, PEARL,
CULTURED PEARL, KESHI PEARL, BLISTER PEARL, MABE PEARL, DYED
PEARL, IRRADIATED PEARL, IMITATION PEARL, ARAGONITE, UNAKITE,
SAUSSURITE, ALBITE, SUNSTONE, AMAZONITE, ADULARIA, MOONSTONE, ORTHOCLASE
NOBLE, MAW-SIT-SIT, POLLUCITE, NATURAL GLASS, GOLDSTONE, LIMORI
STONE, OBSIDIAN, SNOWFLAKE, TEKTITE, MAGNESITE, THOMSONITE,
LEUCITE, PETALITE, LAPIS LAZULI, DYED LAPIS LAZULI, IMITATION
LAPIZ LAZULI, CHRYSOCOLLA, HAUYNE, TUGTUPITE, CALCITE, CORAL
CALCIUM CARBONATE, SODALITE, NATROLITE, PLASTIC, CELLULOIDE,
BAKELITE, BLACK OPAL, OPAL, COMMON OPAL, PRECIOUS OPAL, FIRE
OPAL, MATRIX OPAL, BOULDER OPAL, OPALIZED ORGANIC MATERIALS,
SYNTHETIC OPAL, IMITATION OPAL, SLOCUM STONE, FLUORITE,
ANGEL'S SKIN, ANTIGORITE, ANYOLITE, AVENTURINE
FELDESPAR, BASALT GLASS, BLENDE, BLOODSTONE, CALIFORNITE,
CHLOROMELANITE, CHRYSOTILE, CINNAMON STONE, CROSS STONE, DISTHENE,
EILAT STONE, FABULITE, FIBROLITE, GOSHENITE, HEMATINE, KORITE,
LEUCO GARNET, MALI GARNET, MANDARIN, MARCASITE, MAXIXE AQUAMARINE,
MELANITE, METAJADE, MICROCLINE, MOLDAVITE, MOMO, MORION, MORO,
ODONTOLITE, OLIVINE, ONYX MARBLE, OPALITE, OX-BLOOD, REINDEER
STONE, SARDEGAN, SEA OPAL, SPECTROLITE, STICHTITE, TITANITE,
TOPAZOLITE, TRANSVAAL JADE, TUFA, VERDELITE, VESUVIANITE,
VICTORIA STONE, VIOLANE, WATER-SAPPHIRE, WILLIAMSITE, WYOMING
JADE, ... / ... gem identification chart or properties
list and table for the easiest gem identification , ..../
...synthetic gemstone, imitation and treated gems
are easily separeted with this gemstone property table.
A - practical orientation, B all the distinctive
tips and tricks for gemstone identification, C ... / ... gem
chart, blue chart, gembluechart, gemstone identification bluechart,
gemchart or gem table are common denominations for this
new, complete and up-to date property chart ... / ... practical
orientation for a secure gemological diagnostic, ...
/ ... with this gemmological properties table
with focus: A on treated gems, B on synthetic
gemstones, C on imitation material. ...
/ ... Gem imitation as well as synthetic, assembled doublet,
triplet " gemstones " will be easily identifyed, ...
/ ... nicolas gem chart, a realy useful tool for
gemological classe, school and institute , .../... are
we facing a natural, heat treated gem ? What kind of
treatment are possible for this particular gemstone
? Irradiation is for example commonly used to enhance
the pink tourmaline... but how can one make the diference
between a natural and a irradiated material ? This is not
always possible for example in the case of the yellow beryl
which ... / ... a gemmological tool for an easy
distinction between most gem material available on the market,
....// .... gemstone property list in order
to get A , the quicker and more accurate identification and
B, the most complete reference ... / ...
Streak : Greenish to brownish black / Misnamed
marcasite, closely related mineral ...SG 4.80 - 4.92, (Orthorhombic).../ ...Imitated
by man-made "hematine": Mainly constituted of stainless steel.../...
Gem table : Less transparent than diamonds under UV ; Also
Heavy liquid separation: Methylene iodine : SG 3.32... /...Natural
rutile occurs in dark yellowish brown, reddish brown to black
colour.../ ... with this gemstone analysis tool ...
/ ... Naturals: Bearding, frosted girdle, trigons, crystal
inclusions / "Cape" diamonds usually show lines
in blue spectrum... / ... with this gemstone property
chart, you will learn that the intense yellow diamonds fluoresce
yellow and do not show absorption bands... / ...common
imitations: Cubic Zirconia, Moissanite (May react the same
way on old diamond testers) / May be fracture filled:
Orange to purple flash effect seen parallel to fracture, .../...show
"umbrella effect" around culet or "ring effect" around girdle...
/ ...May be laser drilled to remove black spots: Channel(s)
may be seen.../... Irradiated blue diamond doesn't phosphoresce,
remains opaque under SW UV, ... Irradiated black shows
a dark greenish tinge in transparency.../... Irradiated diamond
spectrum: May show a distinctive narrow line in the yellow
at 594 nm (+ lines in green at 504 and 497), with or without
"cape" lines.../... Irradiated black shows a dark greenish
tinge in transparency...
... FABULITE / Brittle unlike diamond
it imitates, may show rounded facet junctions and polishing
lines.../... BLENDE / Very strong dispersion
/ Colour zoning / Perfect cleavage: 6 directions
/ Common inclusions: Dark brassy yellow chalcopyrite.../...Strong
doubling of back facet junctions / Brittle ...
/ ...May show misleading feathers-like inclusions).../...,
May show colour banding / (Fluid inclusions, greenish
transparent needles of tourmaline,.../...TITANITE
/ Common inclusions of actinolite needles.../...Yellow
variety: TOPAZOLITE: See grossular page 2 / Black
variety: MELANITE / Reddish brown variety may
show chatoyancy.../...red-end at 701 nm (Chromium spectrum);
Weak to strong red reaction through chelsea filter.../ ...Byssolite:
"Horsetails" ... / Spectrum characterized by an absorption
band in the blue (+/- 445 nm); .../ ...May show misleading
flux inclusions: Feathers, linear arrangement of tiny grains...
/ Green garnets imitation: Red through chelsea filter
(Chromium), .../...Usually too dark to be faceted /
See gahnospinel page 2 / (Synthetic : RI: 1805,
SG: 4.40) Spinel group.../... Sharp cat's eye
/ Fiberoptic glass: Fibres are stacked in hexagonal
or cubic.../... Abraded facet junctions, (brittleness increasing
with heat-treatment) /... May show a typical "jailhouse" spectrum.../...
Blue, golden, colourless zircons are commonly produced by
heat-treatment of a reddish brown variety: Blue colour may
fade.../ ... Metamisation: Disintegration of the high
type crystal structure up to the almost isotropic low type
/... / gem stone... . / Low type: Repeated
twining and - or zoning, .../
... sapphire typical inclusions: "Fingerprint" or "fly's
wing-like" inclusions / Rutile needles (also
ilmenite) usually as "silk" intersecting at 60°-120°, crystals
of apatite, calcite, dolomite,... / Straight or angular
colour zoning /... Colourless sapphire fluorescence:
Commonly weak to moderate orangy red under SW, .../ ...Yellow
and padparadscha sapphire may result from irradiation (Colourless
to light yellow can turn into yellow, pink into padparadscha):
Colour often unstable, fading with ...
...Distinctive inclusion: "Silk": ... / ... may
be glass filled: Distinct surface luster (Gas bubbles may
be seen) / ... if dyed: Colour concentration may
be seen in cracks and .../... very common / Melted
crystals: Rounded, may have snowball appearance; Commonly
surrounded by discoid fractures (Tension cracks) /
Partially disolved "silk" (Dot-like).../...flux remnants.../
... in blue sapphire from madagascar... / ... which is the
case in surface reaching cracks (ruby) / May fluoresce
chalky green under SW, (blue sapphire, padparadscha, ...
... from the culet with diffused transmitted light: Colour
concentration at facet junctions, in cracks, around girdle,
uneven facet to facet colour distribution.../ ... Colourless
sapphire fluorescence: Commonly weak to moderate orangy red
under SW, .../... in ruby from Burma ( Myanmar )Yellow and
padparadscha sapphire may result from irradiation (Colourless
to light yellow can turn into yellow, pink into padparadscha):
Colour often unstable, fading with .../ ...Distinctive
inclusion: "Silk": ... / ... may be glass filled: Distinct
surface luster (Gas bubbles may be seen) / ...
if dyed: Colour concentration may be seen in cracks and.../...
very common / Melted crystals: Rounded, may have
snowball appearance; Commonly surrounded by discoid fractures
(Tension cracks) / Partially disolved "silk"
(Dot-like)... flux remnants
... in surface reaching cracks (ruby) / May fluoresce
chalky green under SW, (blue sapphire, padparadscha, .../ ...
diffused star: Very thin fabric structure: Shallow fuzzy whitish
surface layer under fiber-optic light. Unlike natural, the
rays may not be... / ...(hexagonal) colour banding.../ ...
curved growth lines and colour banding (Diffused light),
gas bubbles / Boehmite needles, cracks (and "feathers"
!) may be induced (Ruby).../... unlike most of
unheated natural / Colourless commonly weak bluish
white under SW UV .../... white to orangy flux inclusions
often in misleading "fingerprint" pattern, especially in the
case of rubies : .../... hexagonal and triangular platinum
platelets.../... (Manganese aluminium silicate) /
"Fingerprint" inclusions, rutile needles... / ... variety:
MANDARIN.../... pyrope-spessartite garnet commonly mixed in
lower proportion with almandine and grossular garnet...
/ Spectrum: .../... in addition to malaya spectrum
a broad absorption band in the yellow .../... difference between
these 3 garnets depends on the iron and magnesium proportion:
Iron = almandine, magnesium = pyrope. The intermediate garnets,
+/- 1.745 -1.765, are called.../... hydrogrossular
/ MALI GARNET: Yellow to greenish brown variety mixed
with andradite garnet (+/-20%, page 1): Commonly shows
RI of +/-1.772, SG of +/-3.68 / Colourless variety:
LEUCO GARNET.../... ( CINNAMON STONE ) / Magnification:
Characteristic "heat-wave" effect, oily appearance /
Rounded crystal of apatite, calcite, zircon /
Inert under .../... "feathers" of tiny negative crystals,
fluid inclusions, ... / Chelsea filter: May react pinkish
to red, depending on chromium content / Common
imitation: YAG page .../... clouds of tiny needle-like
rutile inclusions; Actinolite, goethite needles, liquid fingerprint,
2 phase inclusions / Yellow, green and brown:
Typical spectrum: Absorption band in .../...Transition between
gahnite and spinel.../... Strong pleochroism: Blue - colourless...
/ Common inclusions of tiny white crossite fibers.../...
used as amulets: "CROSS STONE" :See chiastolite p. 4 /
Transparent dark brown crystals have been cut; Spectrum: Strong
line in the blue (450 nm).../... Epidote group and species,
.../... imitations: C-C garnet, synthetic spinel & sapphire,
C-C tourmaline (p.4), .../... may intergrow with malachite
(page 3): AZURMALACHITE, .../... translucent to opaque massive
grossular garnet: Inclusions: Black specks of magnetite
/ Often miscalled "transvaal jade" /
Pink variety: RI and SG on ... /... may intergrow with idocrase
and.../... parallel rows of tiny spinel octahedrons or dolomite
rhombohedrons. / Gemological Instruments .... / ...
Blue: Rarely coloured by cobalt: Pinkish through chelsea filter,
.../ ... blue: Pinkish through chelsea filter: Imitates
aquamarine, sapphire, .../... : Pinkish to red reaction due
to Cobalt: Typical spectrum: 3 broad bands; One centered in
the orange, one in the yellow and one in the green.../...
"True" cat's eye due to numerous minute tubular cavities or
acicular crystals parallel to optical axis / Inert
under SW and LW / Imitated by quartz cat's eye
(page 6), man-made glass (limori stone page 7), .../..., (
VESUVIANITE ) / CALIFORNITE: Translucent to opaque
yellow green variety; Typical spectrum: 1 line in the blue,
1 weaker in the green (464, 528 nm) /.../... , ( DISTHENE
) / One perfect cleavage; Low hardness parallel
to crystal length, high at 90° / Strong pleochroism
/ Spectrum: 2 lines in the blue (435, 445 nm)
/ May fluoresce reddish (LW) /.../..., common
ornamental: Massive green with black spots and opaque ruby
inclusions ( ANYOLITE ) / (Epidote group)
... , strong pleochroism: Blue - greenish yellow - purplish
red / Commonly imitated by synthetic forsterite
(See below) / Colour commonly improved by heat-treatment
.../..., commonly intergrowned with quartz p.6 (RI:
+/-1.540: DUMORTIERITE QUARTZ) / Rare in crystal
form: Strong pleochroism .../ VIOLANE: Violet-blue variety
/ CHROME DIOPSIDE: Emerald green: Chelsea filter: Reddish
to .../ ...493 nm) / Inclusions of parallel sillimanite
needles. / .../..., hypersthene commonly showing reddish aventurescence
due to platy inclusions of hematite and goethite. / .../...
: bronzite: Brown body with fibrous inclusions: Bronzelike
submetallic luster / The relative difference between
these three stones depends on the iron and magnesium proportion:
RI and SG increasing with iron content. / ... : typical
spectrum: One strong and one weak line in the green (505,
550 nm) (505 line may also be seen in diopside: See above)
/ Black star: Fuzzy rays; Bronze colour sheen, .../...
, dyed in any colour. / CHLOROMELANITE: Black veined
and spoted variety: See maw-sit-sit p.7 / See
nephrite p.4 / Common imitations: Chalcedony p.6,
bowenite p.5,californite: See idocrase above, hydrogrossular
p.2, saussurite p.7, limori stone p.7, .../... ( FIBROLITE
): Usually cat's eye due to perpendicular greyish hypersthene
fibres and parallel arrangement of rutile needles (Commonly
greyish brown to dark brown)... /... , along cleavage
planes: Perfect prismatic cleavage (2 directions: +/-
90°) / The colour may fade when exposed to sunlight
/ Commonly irradiated to improve the colour or change
the kunzite to the rare hiddenite variety (Colour unstable).../
... emerald green hiddenite showing chromium lines in the
red (690, 686, 669, 646 nm), and a broad absorption
band in the yellow orange (+/- 620 nm); Two lines in the blue
may also be seen (437, 433 nm), .../ ... tests
(SG: 3.90 - 4.00) / May intergrow with azurite
(page 2): AZURMALACHITE, ... / in the case
of a gem tool ... / ... peridot : Doubling / Magnesium
iron silicate: Iron spectrum: Three bands in the blue-green
(453, 477, 497 nm) / Disk-like inclusions ("Lily
pad"), chromite octahedrons, ... / ... Olivine group,
.../... , small needle-like inclusions, striations /
Common imitation of tanzanite / (Natural forsterite
not gem quality) / Synthetic Olivine: See remark
1. /... /... / Sometime called "CROSS STONE":
(See staurolite p.2). / ... copper content, commonly
after heat-treatment / (May be fractured-filled:
See emerald p.5) ... all brownish to yellowish
brown tourmalines tend to be called dravite, belonging or
not to the species. / ... / ...green tourmaline
( VERDELITE ) often shows indicolite spectrum (Also
commonly heat-treated) / CHROME TOURMALINE: Fine
chrome-rich emerald colour: Reddish through chelsea filter...
/ ... perfect cleavage: Two directions /
The fibrous aggregate differs from nephrite by its greater
iron content (More than 5%). ... /... fibrous /
Commonly high dome cut / Sometime called "cat's
eye jade", ... / ... / Black inclusions
common / ( WYOMING JADE: Rich apple-green variety
) / Less commonly dyed than jadeite because of
its more compact structure, may be impregnated: See
jadeite page 3, ... / ... topaz ./
Irradiation followed by heat-treatment routinely produce blue
colour (Light blue also natural), Strong green results
from diffusion process / Pink and purplish pink commonly
produced by heat-treatment of the sherry brown variety: .../.../
...turquoise. May have black "spiderweb" matrix
/ Chelsea filter: No reaction unlike some imitations
like variscite (page 5), dyed howlite (page 5), dyed
magnesite (page 7), etc. / Usually opaque to semi-translucent
under...
... strong transmitted light / Inclusions
of pyrite, quartz, etc / Often dyed: Acetone may
reveal the dye: Depending on coating / Odontolite,
fossil tooth or bone, has been used as imitation: "FOSSIL
TURQUOISE" :RI: 1.600 (1.570 - 1.630), SG:
... / ...("Fish-eggs"; "Cream-of-weat") not seen in natural
turquoise / Usually translucent under strong transmitted
light ,... / ... ( AMBLYGONITE BI - ) / Commonly
light yellow / Perfect basal cleavage /
May fluoresce light green to LW UV or phosphoresce light blue
to both LW and SW UV, ... / ... luster /
Sometime used as jade simulant / Fluorescence:
Common orange to yellow glow under UV light, ... / ... have
black "spiderweb" matrix / Dyed blue to imitate
turquoise (and lapiz): Chelsea filter: Pink to red reaction;
Spectrum: One band in the red and one in the yellow green,
.../ ... spots / Mainly constituted of chromium-rich
mica fuchsite (Lines in the deep red spectrum, commonly
3, may be seen)./ ..., 650 nm) / Chelsea
filter: Pinkish to reddish reaction unlike turquoise it imitates.
/ .../ ... , tube-like inclusions parallel to optical axis
/ Common pleochroism: Colourless to greenish bluish
- blue green to sky blue / Chelsea filter: Greenish
bluish; Synthetic spinel and quartz appear pinkish to red
(Cobalt); .../ ... blue Topaz appears greyish to blue
without greenish through the filter; In addition, it may show
a colourless, pinkish, bluish pleochroism / .../...
/ Often produced by irradiation of goshenite (Commonly
not detectable) / May show planes of tiny two
phase inclusions / Pure yellow also called GOLDEN
BERYL, .../ ... absorption band in the red spectrum
/ Doublets and triplets used to be common: See remark
2 / TRAPICHE colombian emerald: Six green arms
extending from central green core; white impure.../ ... typical
3 phase inclusions (Sometimes jagged), albite, pyrite, calcite
crystals /...
... spectrum: See above: Coated beryl, ... / ... phenakite
crystals with or without extending 2 phase inclusions "Nailhead
spicules" / Small veils of minute liquid inclusions
/ Cellular pattern (Lechleitner) / Hexagonal
and triangular platinum platelets / See remark 1 / ...
AIMERALDA ) / Many kinds: Mainly made of glass,
may contain beryl powder / Veil-like inclusions,
gas bubbles / May be ADR* or show anomalous "aggregate"
reaction / See remark 1 / .../ ... blue to green
labradorescence: With all spectral colours: SPECTROLITE
/ Repeated twinning / Transparent stones:
Common small elongated black inclusions (Ilmenite) /
See moonstone page 7, .../... may be bleached to create the
rare lighter "golden" colour: SG on the low side /
See: Coral calcium carbonate page 8, ...
... commonly red and pink / High
magnification: Grainy structure / See: Coral calcium
carbonate page 8 / .../ ... CHRYSOTILE: Mottled,
veined variety; Common yellow veins on dark green body colour
/ ANTIGORITE: Massive, platy variety / Intense
oily green variety called WILLIAMSITE: Typical inclusions
of dark octahedral ... / ... STICHTITE: Pink red to purple
variety, ... / ...Shell of hawksbill turtle (Endangered
species). Magnification: Colour made of small spherical dot-like
patches concentrated in dark areas, unlike the very common
plastic imitation p.8,... / ...translucent to opaque
violet with white to black swirls, flame-like inclusions:
The "charoite" used in the market is a rock composed of various
minerals (Charoite, feldspar, augite, ... / ...
/ IRIS, RAINBOW quartz: Iridescence due to natural or
induced cracks / Doublet and triplet used to be
common: Emerald imitation, .../ ...,amethyst and citrine.
/ ... "Zebra stripe" inclusions, 2 phase inclusions in
veil-like pattern, .../ ... usually produced by heat-treatment
of smoky amethyst / Commonly sold as yellow topaz
/ Translucent: Chatoyancy & Star ... / ...figure
is missing (Bull's eye): Common in synthetic quartz:
See below.
If twinned:
The black cross center may show a spiral pattern. /...
colour produced by heat-treatment of light amethyst; .../
2 phase inclusions, dark red hematite inclusions, golden yellow
rutile
...very dark stones called MORION /
May be produced by irradiation of rock crystal, ... /
needles, ("Venus hair"), black tourmaline crystals, fibers
of green actinolite, ... / ...very dark stones called
MORION / May be produced by irradiation of rock
crystal, ... /... aventurescence caused by platy inclusions
of mica (Green fuchsite) / Imitated by "goldstone":
See page 7 / See feldspar sunstone page 7 / .../ ...
may closely resemble chrysoberyl cat's eye (page 2)
/ (May be dyed: May show colour concentration at fiber's
ends), .../ ... the original mineral of the veins is crocidolite:
Blue variety of asbestos which advanced decomposition into
silica produce the tiger's eye variety, .../ ... , ( CORDIERITE
) (Improperly called "water sapphire") / Very
strong pleochroism / Typical inclusions: Platelets
of magnetite, Tabular brownish red iron oxide inclusions:
May show glittery effect: BLOODSHOT IOLITE, ... /
... elephant ivory (Endangered species): Intersecting
structural lines (Lozenge pattern): "Engine-turned" effect
/ High magnification: Undulating fibrils structure,
bone imitations showing small dark lines / ...
... tagua nut / Magnification: Parallel
elongated cells / (Shows a weaker fluorescence
than elephant ivory), ... / ... key separation: 1 - Salt
saturated water : Only float amber, copal, polystyrene
2 - One drop of acetone will soften the copal in few seconds:
Becomes .../... sticky unlike "true" amber, and disolve the
polystyrene / .../ ...small amber pieces warmed and
compressed together (Reconstructed) / Immersion
in alcohol reveals hazy outline and different hue of individual
pieces, elongated and flattened gas bubbles, .../ ...
the red: 645, 670, 705 nm: Similar to undyed Jadeite (p.3)
/ Transmitted light: Dye may show a mosaic-like marking,
... / ... sard is darker than carnelian (Dark reddish
brown to brown) / Commonly dyed .../ ... ONYX:
Straight colour bands (Black base and white upper layer)
/ Black chalcedony ("Black onyx") is assumed to
be dyed / SARDONYX: Straight white band of onyx
with brownish red band of sard, .../ ... with the exception
of moss, dendritic, scenic "agate" which should rather be
named moss chalcedony, dendritic chalcedony, etc. /
Routinely dyed .../ ... FIRE AGATE: Iridescence caused by
layers of platy iron oxide crystals: Botryoidal structure,
brown body colour / IRIS, RAINBOW AGATE : diffraction
of light due to bands of transparent fibers closely spaced
.../ ... dyed blue to imitate lapis lazuli (page 8): "SWISS
LAPIS" (Lacks pyrite inclusion), .../... banded structure
/ Often dyed: Acetone test / Commonly used for
carving cameos: White and brown helmet shell and white, orange
and pink conch shell: Common flame-like surface.../ …/
Abalone shell strongly iridescent: Paua variety from New Zealand
exibit a strong blue - green orient: SEA OPAL, .../... ( KORITE
) / Fossilized shell of ammonites in the form
of aragonite: Thin and fragile lamellar structure in a mosaic-like
pattern with opalescent play-of-colour: .../ ... imitations
and nacreless pearls / Routinely bleached to lighten
the dark spots of conchiolin, .../... conch pearl are
non-nacreous (Calcareous concretion) and show a white, orange
or pink colour; SG between 2.81 - 2.87; Most of them show
a porcelain-like surface with typical flame-like marking .../ ...
natural byproduct of the insertion of a cultured pearl's nucleus
.../ ... , and black, typically AKOYA PEARLS (Common
size 3 to 9 mm) / Even colour distribution
/ Colour concentration may be visible around the drill
hole (Magnification) / ... iIrradiation of bleached
pearls to produce "black" pearls / Magnification:
Typical black nucleus and whitish nacre: Separation may be
seen in the drill hole .../ ... made of fish scales (Guanine
crystals): Magnification: No overlaping structure; .../ ...
spot reading : pink areas +/- 1.525 (Feldspar),
white to gray areas +/- 1.540 (Quartz), green
areas +/- 1.760 (Epidote) .../ ... . Alteration
product of feldspar mainly constituted of zoisite: Green areas
+/- 1.700 and albite: White areas +/- 1.525 /
Used as jade substitute .../... common blue sheen: See below
: moonstone, see page 5: labradorite / 2 cleavages
at nearly 90°, one good, one perfect .../... aventurescence
due to platy crystals of hematite and - or goethite: AVENTURINE
/ Imitation: Goldstone: See below / See
page 6: Aventurine quartz / (Feldspar oligoclase),
.../ ... ( ADULARIA ) / White to blue sheen
/ "Centipede" inclusions / (Feldspar orthoclase)
/ See above: Albite, ... , Imitated by: Adularescent
synthetic spinel: SR ADR*, commonly showing a .../... aventurine
feldspar (above) and quartz (p.6) imitation /
Hexagonal or triangular copper platelets reflecting light.../
... partally devitrified glass looking like nephrite: Jadeite
imitation (Metajade); Magnification: Fern-like pattern
/ Imitation of chrysoberyl cat's eye (Victoria
stone) / See remark 1 / .../ ... varieties according
to source: MOLDAVITE, JAVAITE, etc / Torpedo shaped
gas bubbles / Undulating structure with snake-like
pattern / Polariscope: Common spots of light caused
by crystalline particles, ... / ...common imitation
of turquoise, lapis, coral, etc: Chelsea filter: Common reddish
reaction; Common white to blue green fluorescence... / ...in
the market is mixed with chalcedony p. 6 / May
also intergrow with malachite and turquoise: EILAT STONE:
SG up to 3.25. / ... ( REINDEER stone )
/ Common white to black mottling / May contain
black needles or yellow spots / Fluoresces salmon
red to SW, orange to LW / Colour fades temporarily
in darkness , .../ ... perfect and easy rhombohedral
cleavages (3 directions at 74°) / Strongly double
refractive / ICELAND SPAR: Transparent colourless variety
/ Massive variety commonly dyed: Acetone test; Dyed
green to imitate .../ ... such as ANGEL'S SKIN: Pink,
MOMO: Light salmon red, SARDEGAN: Medium red,
OX-BLOOD, MORO: Red, etc / See: Coral conchiolin
and imitation page 5, ... / ... black opal) / ...
/ HARLEQUIN OPAL: Mosaic square-like colour pattern,
CRYSTAL OPAL: Transparent to semi-transparent colourless body
with strong play-of-colour, .../ ... ( MEXICAN OPAL )
/ If synthetic, common RI: +/- 1.410, SG: +/-
1.91, common denditric inclusions, commonly fluoresce weak
to strong bluish white under UV (Natural may fluoresce
weak orange) / See remark 1. / ...
such as "OPALITE": Convincing translucent milky white with
play-of-colour / Magnification: May show spheroid,
columnar structure or painted-like patches of colour
/ See remark 1 / ... fluorescence: Opalite
commonly shows a strong bluish white reaction under LW and
a chalky whitish blue reaction under SW; Natural white
opal may fluoresce white to light blue, yellow, green under
LW and SW, ... / ... ( FLUORSPAR ) / Common parallel
colour zoning / 2-3 phase inclusions /
Perfect and easy octahedral cleavages / Fluorescence:
Common: Green to blue, especially under LW / Colour-change:
Blue (Daylight) -.../ ...lavender (Incandescent light)
/ BLUE JOHN variety: Curved bands of blue, violet, dark
purple / Blue often improved by heat-treatment
/ (Synthetic has been made; RI up to 1.440: Colourless,
red, blue, green, ... / ... . The canadian Gemmologist,
Canadian gemmological association Toronto.
Boletin del Instituto Gemològico Español
Madrid. Gems and Gemology, Gemological Institute
of America Carlsbad, USA .
JewelSiam, Gem and Jewelry magazin
Bangkok, Thailand. Journal of Gemmology, Gemmological
Institute of Great Britain London. La gemmologia,
Instituto Gemmologico Italiano Milan. Revue
de Gemmologie, Association Francaise de Gemmologie
Paris. The Australian Gemmologist, Gemmological
Association of Australia Victoria. Zeitschrift
der Deutschen Gemmologischen Gesellschaft
Idar-Oberstein..../... Gemological Links. Gems and Precious
Stones from ... / ...gemological publication, Gemological
Labs, Gemological Organizations and laboratory and services
for professional Institutes, Labs and Associations.
education and training programs gem and jewelery tools and
equipment, precious and semi-precious gem stones identification
with a practical gem property chart ....
mineral identification tools, Mohs' hardness points, specific gravity testers, UV lights, diamond testers
mineral identification tools and equipment, mineral ID kits, precious stones testers, gem identification tools and equipment, gemstones testers
specific gravity tester, specific gravity of minerals, specific gravity of gems, density, jolly balance, mineral hydrometer, electronic scales, electronic balances
gems Instruments, refractometers, gem refractometers, Chelsea filter, aqua filter, ruby filter, emerald filter gemstone and mineral guides, gem and mineral books, mineral handbooks
http://www.prettyrock.com/php/gem-instruments.htm
gemmology, gemology, refractometer, polariscope, darkfield loupe, carat scales, gem scales, tweezers, dichroscope, tools, gem tools gem tools gems - carat scales, gem handling equipment (tweezers, digital calipers and basic gemmology equipment.
refractive index, refractive index of minerals, refractive index of gemstones, refractive index of gems, double refraction, anisotropic, birefringence, reflective qualities of gems
Gem Enhancement Awareness
It is important for the consumer to be aware of the fact that many varieties of gemstones on the market today have been treated or "enhanced" in order to improve their appearance. Additionally, there is a constant battle between unscrupulous gem traders and testing laboratories to hide and detect new treatments.
consumers should always require disclosure of any alterations or enhancements of a gemstone before making a purchase. This is especially important if the enhancement to the treated stone is not permanent or if the treated stone will require special care.
The Federal Trade Commission (FTC) publishes guidelines for the jewelry trade, stating that consumers must be informed of any gemstone treatments that are not permanent OR that "significantly affects" the value. Most comprehensive gemological reports identify treatment types, and when purchasing a large, expensive stone it is advisable to have a full GIA or AGS report done.
Gem Enhancement Classifications
The designation for identifying enhancements on a gemological report is: "N" (not enhanced), "E" (normally enhanced), and "T" (nontraditional enhancements). Commonly used methods of enhancement are:
Semi-Permanent or Temporary Gem Enhancements
Bleaching (B): Used to lighten and/or whiten gemstones or pearls
Coating (C): Surface enhancement by enameling, inking, foiling, lacquering, sputtering, or vapor deposition
Dyeing (D): Used to enhance the color and uniformity of gemstones or pearls
Filling (F): Filling surface cavities or fissures with colorless glass, plastic or resin
Impregnation (I): Treating gems with oil, wax, or resin to improve clarity & appearance
Waxing (W): Impregnation with colorless wax, paraffin or oil
Permanent Gem Enhancements
Flux Healing (FH): Heat enhancement used to heal fissures and fractures
Fracture Filling (F): Injecting plastics or glass into fractures
Heat Treatment (H): Used to lighten, darken, or alter color
Irradiation (R): Used to add color intensity to diamonds, gemstones, or pearls
Lattice Diffusion (U): High-temperature heat treatment to produce color and/or asterism
Lasering (L): Laser and chemical treatment to remove inclusions
Most of the 'temporary' enhancements or treatments are basic and self-explanatory, but most of the 'permanent' gem enhancements involve highly sophisticated techniques that can be difficult to detect. Most treatments leave some kind of telltale signature or fingerprint, but as treatment methods become increasingly subtle, they are more problematic. Some of the more involved treatments and enhancements are listed below. These treatments are permanent, but can have a significant impact on the value of a gem.
Flux Healing
Flux healing involves the filling of surface cracks, cavities, and/or inclusions by exposing the crystal to a combination of heat and borax or other fluxes and solvents to fill voids with molten low-viscosity flux glass. As the flux mixture fills a fracture via capillary action, the molten mixture dissolves the walls of the fracture until the liquid in the crack becomes saturated with the actual mineral's molten solution.
Heat Treatment
Heat treatment or 'annealing' is done using a combination of chemicals (beryllium, borax, lead, tantalum) and heat to permanently alter a stone's color. Heating or "cooking" the stone is done at temperatures ranging from 450º to 1850º Celsius for a period of 2 to 12 hours or more. One telltale sign of heat-treatment is the presence of small fractures or "decrepitation feather" within the stone that appear around natural mineral inclusions.
High-Temperature High-Pressure (HTHP)
High-Temperature (2,000º C) High-Pressure (70,000 atmospheres) treatment or HTHP was developed by General Electric in 1999, to lighten or totally remove a brownish hue in some Type IIa diamonds. Type I diamonds have nitrogen impurities that absorbing some of the blue light spectrum, thereby making the diamond appear yellow, while Type II diamonds have structural defects (aka plastic deformations) created during crystal growth, that can cause a brownish color. High-Temperature High-Pressure treatment can in some cases 'repair' these deformations, whitening the diamond's appearance.
Type I diamonds which have nitrogen impurities can also have their color altered using High-Temperature High-Pressure treatment. Using HTHP, a company called Nova Diamond creates fancy colors in vivid hues of yellow and green, bypassing the need for irradiation.
Diamonds treated by General Electric (Pegasus Overseas Ltd) to remove coloration have the logo "GE POL" laser-inscribed on the girdle, but laser-inscriptions can be removed by polishing. Detection of non-inscribed HTHP treated diamonds is accomplished by gemological testing laboratories using photoluminescence spectroscopy, 'Fourier Transform Spectroscopy' (FTIR) and 'Raman Spectroscopy' to analyze visible and infrared light absorption looking for telltale absorption lines that would indicate high temperature exposure. Additionally, telltale fingerprints that can be seen under a microscope may include dark cracks around inclusions, internal graining, haze, and partially healed feathers.
Irradiation
Irradiation treatments involve exposing the stone to electromagnetic rays (ionizing radiation) or gamma rays (cobalt 60 radiation) to release electrons from their normal location, moving them to more desirable color-producing locations. Depending on the mineral to be treated, and the desired color alteration, alpha particles, beta particles, electrons, gamma particles, neutrons will be used in the irradiation process. Irradiation treatment uses a linear accelerator to expose the stone to high-energy electrons, a cyclotron for charged high-energy particles such as protons, or an electron-beam nuclear reactor to expose the stone to high energy neutrons. Neutron bombardment and electron bombardment are the two main irradiation methods practiced today.
Residual radioactivity in the stone can be a potential concern. The use of a nuclear reactor can create radioactive isotopes in the stone, necessitating storage for a sufficient amount of time for the decay of any residual radioactivity.
Lasering & Laser Drilling
The laser-drilling of diamonds to reduce or remove foreign crystal inclusions, or iron-oxide stained fractures, has been preformed for over 20 years. Drilling is accomplished using an infrared laser to bore microscopic holes (0.005" diameter) into a diamond, creating an access channel to the inclusion. The diamond is then immersed into a sulfuric acid solution to dissolve any non-diamond crystals and/or staining. The laser-drilling process is followed by glass in-filling to hide the channel, using a glass material with a refractive index that approximates diamond. Several inclusions can be removed from the same diamond using this technique.
Visible signs of laser-drilling and subsequent glass-filling can easily be detected under a microscope, and may include semi-opaque white lines that are straight or slightly wavy in appearance, air bubbles and/or flow-lines within the glass-filled hole, and dark circles where the holes breach the diamond's surface.
Lattice Diffusion
Lattice diffusion is a treatment process using a combination heat and chemicals to 'diffuse' or deposit an element (beryllium, chromium, vanadium, etc.) from an external source into a gemstone in order to alter or improve its color hue or saturation. This treatment is used primarily on corundum (rubies and sapphires) and is considered an unethical practice. Diffusion is a mechanical process where atoms and/or ions move through solid matter. Within a crystal's lattice structure there are missing atoms called "vacancies" that can be filled with a new element's atoms, thereby changing the chemical composition and color of the mineral.
Lattice diffusion can be difficult to detect, and therefor, is considered an unethical practice. The diffusion treatment of ruby and sapphire in-particular is major concern within the gem trade.
Gemstones & Their Treatment Types
Most gemstones, with the notable exception of garnet, have a particular treatment, or series of treatments that are commonly used to increase the marketability of the stone. This list represents common gemstones and the typical treatments they receive.
Alexandrite: None
Amethyst: Heat Treatment
Aquamarine: Heat Treatment
Coral: Dyeing
Druzy Quartz: Dyeing, Heat Treatment, Irradiation, Vapor Deposition
Citrine: Heat Treatment
Diamond: Irradiation, Lasering
Emerald: Filling, Impregnation, Waxing/Oiling
Garnet: None
Lapis Lazuli: Dyeing
Onyx: Dyeing
Opal: Filling, Impregnation, Waxing/Oiling
Morganite: Irradiation
Pearls: Bleaching, Dyeing, Irradiation
Peridot: Impregnation, Waxing
Rubelite: Heat Treatment
Ruby: Heat Treatment, Flux healing, Fracture Filling
Sapphire: Heat Treatment, Flux healing, , Fracture Filling, Lattice Diffusion
Spinel: None
Tanzanite: Heat Treatment
Topaz: Heat Treatment, Irradiation
Tourmaline: Heat Treatment, Irradiation
Zircon: Heat Treatment
Conclusion
There is nothing intrinsically wrong with gem enhancements as long as you are made aware of their use. New treatments are being developed all the time, and gemological testing centers are constantly revising and updating their testing regimes to combat the unidentified enhancement that can slip through the cracks. As consumers, we must rely on the testing laboratory's ability to identify enhancements so that a gem's value can be properly ascertained before a purchase is made.
Gemological Testing Equipment
lattice diffusion, laser drilling, irradiation, high-temperature, high-pressure (HTHP), heat treatment, flux healing, fracture filling, permanent gem enhancements, waxing, impregnation, filling, dyeing, coating, bleaching, permanent or temporary gemstone enhancements