Gemstone Names

Example:

Nickname - Real Gemstone

African emerald - Namibian green fluorite
Alaska Black Diamond - hematite
Alexandrine - color change lab imitation alexandrite (lab corundum usually)
Amazon jade - amazonite
Amegreen - amethyst and prasiolite
American ruby - almandine garnet, or rose quartz
Arkansas diamond - usually quartz from Arkansas, though occasionally can be actual diamond
Atlas pearls - white satin spar calcite
Aura quartz (aqua aura, angel aura, titanium flame aura and others) - Quartz treated with permanently bonded metals such as gold, silver, titanium
Australian jade/turquoise - a material found in Australia, probably variscite
Australian ruby - garnet

Gemstones - B

Balas ruby - red spinel (traditional, though incorrect name for red spinel, dates to Middle Ages)
Bastard emerald - peridot, green quartz, or nearly any green stone
Bengal amthyst - purple sapphire
Berilo - green apatite
Biron emerald - synthetic emerald
Black amber - jet
(Alaska) Black diamond - Hematite; or real diamond with numerous black inclusions
Black Hills ruby - garnet
Black Labradorite - larvikite
Black Moonstone - larvikite
Blue alexandrite - color-change sapphire
Blue malachite - azurite
Blue moonstone - blue-stained chalcedony
Blue obsidian - (most) manmade glass
Blue talc - kyanite
Bohemian crystal - moldavite
Bohemian diamond - quartz
Bohemian emerald - green fluorite
Bohemian garnet - pyrope garnet (primarily from the Czech Republic)
Bohemian ruby - red garnets
Bohemian topaz - citrine
Bottlestone - moldavite cut gems
Bristol diamond - quartz
Broghton emerald - green glass
Burma sapphire - lab-grown blue corundum
Buxton diamond - quartz

Gemstones - C

California jade - californite
California moonstone - chalcedony
California ruby - pyrope garnet
Canadian lapis - sodalite
Cape amethyst - light colored amethyst or banded/chevron amethyst
Cape emerald - prehnite
Cape May diamond - quartz
Cape ruby - pyrope garnet
Carbuncle - garnet usually, or other red gem stone
Carthaginian Carbuncle - garnet
Ceylon diamond - colorless zircon
Ceylon opal - moonstone
Ceylon peridot - yellowish-green tourmaline
Champlain marble - massive dolomite from Vermont
Chinese charoite - fluorite
Chinese turquoise - can be any number of things including calcite/quartz/blue-dyed-soapstone
Chrome Garnet - uvarovite
Cinnamon stone - hessonite 
Colorado diamond - smoky quartz
Colorado jade - green microcline feldsapr
Colorado ruby - pyrope garnet
Colorado topaz - citrine
Copper malachite - chrysocolla
Cornish diamond - quartz
Crab fire agate - carnelian (probably enhanced)
Crystalline emerald - quartz
CZ Diamond - cubic zirconia

Dauphin diamond - quartz
Desert amethyst - solarized glass
Diamond - There are many misleading trade names given to diamond imitators, such as: Diagem, Diakon, Dialite, Diamanite, Diamite, Diamogem, Diamonair, Diamonaura, Diamon-brite, Diamone, Diamonesque, Diamonette, Diamonflame, Diamonique I II and III, Diamonite, Diamonte, Diamontina, Diamondite, Diamothyst, Diarita, Di'Yag, Djevalite, 
Delta pearl - imitation pearl

Gemstones - E

Emeraldite - green tourmaline
Emerald of the Urals - demantoid garnet
Emerald malachite - green fluorspar
Endura emerald - green glass emerald simulant
Evening emerald - peridot

Gemstones - F

Faience lapis - ceramic
Fashoda ruby - iron-rich pyrope garnet
Ferrer's emerald - green glass emerald simulant
Fictile ivory - plaster-of-paris imitation of an ivory carving
Fire jade - looks like tiger's eye, mainly opal
Fire pearl - billitonite
Finder's diamond - colorless topaz
Flower sugilite - lepidolite
Fossil turquoise - odontolite
Fukien jade - soapstone

Gemstones - G

Gaia Stone - manmade green glass possible made from Mt. St. Helen's ash
Garnet jade - massive green grossular garnet
Geneva ruby - laboratory created ruby
German diamond - quartz
German gold - amber
German lapis - see Swiss lapis, sodalite, or jasper
German silver - a white metal alloy of nickel, copper, and zinc
Gibsonville emerald - green quartz
Gilson emerald - synthetic emerald
Glass agate - obsidian
Gold sapphire - lapis with flecks of pyrite
Gooseberry - grossular garnet
Grape Garnet - purplish red garnet

Gemstones - H

Hawaiian Diamonds - quartz
Hawaiite - peridot from Hawaii
Heinekenite - false green moldavite
Herkimer diamond - quartz from Herkimer County, New York is the original and increasingly similar looking quartz from other places
Hinjosa topaz - yellow quartz
Honan jade - soapstone
Hope sapphire - synth blue spinel
Honan jade, Hunan jade - soapstone
Horatio diamond - quartz
Hot Springs diamond - quartz
Hyacinth topaz - hyacinth (zircon)

Gemstones - I

Iceland agate - obsidian
Indian emerald - dyed green quartz or chalcedony
Indian jade - aventurine
Indian topaz - yellow sapphire
Iolite - gemmy cordierite
Irish diamond - quartz
Italian lapis - blue dyed chalcedony or jasper
Isle of Wight diamonds - quartz

Gemstones - J

Jade tenace - saussarite
Jadine - Australian chrysoprase
Jasper jade - green jasper or serpentine
Jeweler's topaz - citrine
Jourado diamond - colorless synthetic spinel

Gemstones - K

Kandy spinel - reddish-violet garnet from Sri Lanka
Killiecrankie diamond - colorless topaz from Australia
Kimberly emerald - synthetic emerald
King topaz - yellow sapphire
Korea jade - loose term for nearly any green stone and/or impure jade

Gemstones - L

La beau pearls - imitation pearl
La tausca pearls - imitations
Lake George diamond - quartz
Lake Superior fire agate - glass opal simulant
Lennox emerald - synthetic emerald
Lilac Stone - lepidolite
Lithia amethyst - spodumene, variety kunzite
Lithia emerald - spodumene, variety hiddenite
Lux sapphire - cordierite (iolite)
Lynz sapphire - cordierite (iolite)

Gemstones - M

Madeira topaz - citrine
Malaia or Malaya Garnet - umbalite garnet
Manchurian jade - soapstone
Mari  diamond - quartz
Matura diamond - colorless zircon
Medina emerald - green glass
Meru sapphire - blue zoisite
Meta-jade - Japanese glass jade simulant
Mexican agate/jade/onyx - massive/banded calcite
Mexican diamond - quartz or danburite
Mogok diamond - colorless Burmese topaz
Mojave moonstone - lilac-tinted chalcedony from Mojave Desert area
Montana jet - obsidian, from Yellowstone Park
Montana ruby - red garnet

Gemstones - N

Nerchinsk aquamarine - blue topaz
Nevada black diamond - obsidian
Nevada lapis - a form of chalcedony (not from Nevada, either)
Nevada topaz - smoky obsidian
Nevada turquoise - variscite or sometimes real turquoise
New jade - serpentine (or sometimes bowenite)
Night emerald - peridot
Nickel silver - nickel, copper, zinc alloy of silver

Gemstones - O

Occidental cat's eye - quartz
Occidental diamond - quartz
Occidental topaz - citrine
Oil pearl - mother-of-pearl from a sea snail
Olivene - demantoid garnet aka Olivine
Opal glass - glass imitator of other stones, but not opal
Orange topaz - brownish-yellow quartz
Oregon jade - dark green plasma variety of chalcedony, jasper
Oregon moonstone - chalcedony
Oriental emerald - green sapphire
Oriental garnet - almandine

Gemstones - P

Palmyra topaz - pale yellow heat-treated amethyst/citrine
Paphros diamond - quartz
Pecos diamond - quartz
Pectolite jade - pectolite
Pedrara onyx - stalagmitic marble from Mexico
Pink moonstone - opalescent pink scapolite
Pomegranate ruby - red spinel
Praetorianite - massive grossular green garnet aka Transvaal jade

Precious Garnet - deep red almandine garnet
Prismatic emerald - euclase
Prismatic moonstone - chalcedony
Prismatic quartz - cordierite
Pseudochrysolite - moldavite
Pseudoemerald - malachite
Pyroemerald - green fluorite
Quartz topaz - citrine

Gemstones - R

Radium diamond - smoky quartz
Rainbow magic diamond - synthetic rutile
Red jade - reddish quartzite, and the red variety of dumortierite in quartz
Regency emerald - synthetic emerald
Rhine diamond - quartz
Rhodolite Rose - pink grossular garnet
Rhyolite glass - obsidian
Rock crystal - colorless quartz
Rocky Mountain ruby - garnet
Rock ruby - pyrope garnet
Rose kunzite - synthetic pink sapphire
Rosolite - pink variety of grossular garnet
Rozircon - rose-colored synthetic spinel
Rubicelle - yellow-orange spinel
Ruby balas - red spinel
Ruby spinel - red spinel

Gemstones - S

Sacred turquoise - smithsonite
Salamanca topaz - fiery-colored citrine
San Diego ruby - red tourmaline
Sapphre - Kyanite
Schaumberg diamond - quartz
Scotch topaz -  citrine, or smoky quartz
Scottish topaz - quartz
Serpentine jade - bowenite
Shanghai jade - steatite or talc
Siberian ruby - pink or red tourmaline
Sicilian marble - white Italian marble clouded with greyish veins
Siliceous malachite - green chrysocolla
Smoky Citrine - smoky Quartz
Smoky Topaz - smoky quartz
Soochow jade - bowenite or steatite
South African emerald - green fluorite
Swiss jade - green-stained jasper
Swiss lapis - blue dyed chalcedony or jasper
Synthetic alexandrite or aquamarine -  often synthetic corundum or spinel

Gemstones - T

Tasmanian diamond - quartz
Tecla pearls - imitation pearls that are solid or wax filled
Tokay lux sapphire - Hungarian black obsidian
Topaz cat's eye - yellow girasol sapphire
Topaz quartz - brownish-yellow quartz
Topaz saffronite - brownish-yellow quartz
Tourmaline green - synthetic dark-green spinel
Transvaal emerald - green fluorite
Transvaal jade - massive green grossular garnet
Trenton diamond - quartz

Gemstones - U

Uralian emerald - demantoid garnet
Uralian sapphire - blue tourmaline
Utah turquoise - variscite

Gemstones - V

Vallum diamond - quartz
Vanadium emerald - green beryl colored with vanadium
Verdelite - green tourmaline
Vesuvianite jade - californite
Vienna turquoise - glass imitation of turquoise
Volcanic chrysolite - idocrase or vesuvianite

Gemstones - W

Washita diamond - quartz
Water chrysolite - moldavite
Water sapphire - cordierite (iolite)
White garnet - leucite
Wyse ruby - laboratory created ruby

Gemstones - Y

Yaqui onyx - a marble from Baja and Mexico
Yava onyx - marble from Yavapai County, AZ

Gemstones - Z

Zabeltitzen diamond - quartz
Zircon spinel - synthetic blue spinel