Gemstone Collection (page 6)

Imitation emerald
A faceted teardrop synthetic emerald

Moodstone cut as cabochons. A cabachon is a highly polished convex-cut gem

Green demantoid garnet in ring from the collection of Sir Arthur Herbert Church. Dementoid is the green variety of andradite garnet

Brewster Angle Meter
Placing a gem inside a Brewster Angle Meter. This instrument was introduced in 1999. This instrument can be used to find the refractive index (RI) of gems, which can help with identification

Opal doublets
Opals are not truely crystalline and are therefore mineraloids. They comprise of (hydrated silica glass)

Pink rubellite tourmaline
Chinese pendant carving in pink rubellite tourmaline

Emerald on calcite
Well-formed hexagonal crystals of emerald on calcite. Emerald is a variety of beryl (beryllium aluminum silicate). The green colour is attributed to small amounts of chromium

Topaz
Image of Queen Victoria carved in topaz. Topaz comprises of (aluminum silicate fluoride hydroxide)

Almandine garnets
Brooch set with almandine garnets. Almandine comprises of (iron aluminum silicate) and is the most common of the garnets

Sapphire crystal
Sapphire is a blue variety of corundum, which is the second hardest natural substance known on Earth. Specimen originates from Olberg, Rheinland, now at the Natural History Museum, London

Ruby is a variety of corundum, which is the second hardest natural substance known on Earth. Specimen is originally from Aust-Agder, Norway, and is now on display at the Natural History Museum, London

Beryl
A specimen of beryl (beryllium aluminum silicate). There are several varieties of beryl, aquamarine (blue), emerald (green), goshenite, heliodor and morganite

Emerald, a variety of beryl
A cut teardrop stone and a prismatic crystal of the green variety of beryl (beryllium aluminum silicate) known as emerald. Specimen from the Natural History Museum, London

Almandite
A crystal and a cut stone of almandite, a deep red garnet comprised of (iron aluminum silicate). Specimen from the collections of the Natural History Museum, London

Amethyst is the purple variety of quartz (silicon dioxide) and is a popular gemstone

Tourmaline
A specimen of the mineral and gemstone tourmaline from Itambacury Theophilo Ottoni, Minas Gerais, Brazil

Benitoite cut stone
Benitoite was discovered in 1906 near the San Benito river in California which remains the only known locality for this (barium titanium silicate mineral)

Orange sapphire
A rare Sri-Lankan hexagonal cut orange sapphire. Sapphires belong to the corundum group - the second hardest mineral group known

Sinhalite
A round mixed cut of 15.5 carats. Silhalite comprises of (magnesium aluminum borate) and only known to derive from the gem gravels of Sri Lanka

Beryl
From left to right, different varieties of berly (beryllium aluminum silicate) cut stone; emerald, aquamarine, morganite and heliodor

Diamond
A form of carbon. The brilliant, hard diamond, is formed under conditions of vast pressure and heat deep wihtin the earth

Black Opal cabochon
A specimen of black opal cabochon from Wallangulla, Queensland, Australia. Opal is not a single crystal, but is made up of tiny spheres of silica

Garnet

Cordierite variety Iolite
It is famous for its pleochroism, appearing intense blue in one direction but becoming almost colourless as the stone is turned. Cut stone, faceted girdle, 19.69 ct

Topaz crystal
An imperial topaz crystal from Brazil, length 101mm long. Topaz comprises of (aluminum silicate fluoride hydroxide)

Some crystal forms of carbon
Seen here are rough diamonds or boarts surrounding a diamond crystal which have been photographed on a base of graphite. Diamond is the hardest known mineral on Earth

Kornerupine (magnesium aluminum iron boro-silicate hydroxide) is a rare boro-silicate mineral which occurs in a range of greens and browns - this emerald colour is exceptional

A large cut citrine
Citrine is the yellow and orange variety of quartz (silicon dioxide). Specimen held at the Natural History Museum, London

Citrine and sapphire
Fine and poor examples of gem cutting and polishing. A superbly cut citrine (a yellow variety of quartz) and a poorly cut sapphire (blue), a variety of the mineral Corundum (aluminium oxide)

Fibrolite is an aluminium silicate. It is a rare variety of the mineral sillimanite. This stone from Burma shows blueish-violet and pale yellow pleochroic colours

Andalusite cut stone
Andalusite is an aluminium silicate. It shows spectacular red and green pleochroic colours

A group of feldspar specimens
Amazonstone crystals and gems, pin set with sunstone, and moonstones. The feldpars are significant rock building minerals

Carved nephrite
A tiki from New Zealand (left), a seal from British Colombia, and a Chinese vase all carved from nephrite. Nephrite is actually not a mineral outright, but is a variety of the mineral actinolite

Turquoise vein in shale
Turquoise (hydrated copper aluminum phosphate) vein in shale, from Victoria, Australia. Turquoise is perhaps the most valuable non-transparent mineral

A collection of turquoise specimens
Rough, polished and worked specimens of turquoise (Hydrated Copper Aluminum Phosphate). Turquoise is perhaps the most valuable of the non-transparent minerals

Turquoise
Four different examples of worked turquoise. Turquoise (hydrated copper aluminum phosphate) is perhaps one of the most valuable non-transparent minerals

Tourmaline crystal
A bi-coloured pink and green tourmaline crystal from California

Demantoid garnet cut stone
Demantoid is a variety of andradite garnet. It is green in colour, sometimes with yellow shading

Faceted chrysoberyl
Two cut stones of the gemstone chrysoberyl (beryllium aluminum oxide). This stone is also known as cats eyes

Brown and blue zircons
Natural brown and heat-treated blue zircons. Zircon comprises of (zirconium silicate) and is not the same as the artificial gem cubic zircona

Chrysoberyl cats eyes
Two stones of Chrysoberyl (beryllium aluminum oxide), illustrating the similarity the gemstone has with a cats eye

Zircon crystal
Zircon comprises of (zirconium silicate) and is not the same as the artificial gem cubic zircona. Specimen is from Norway

Garnet cut stones
Grossular (calcium aluminum silicate) and demantoid cut gems resting on andradite (calcium iron silicate) crystals. All of which are types of garnet

Quartz box and carved lizard
An ornamental box set with different quartz stones (silicon dioxide) including a large central citrine together with a carved lizard in cat s-eye quartz

Fluorescent group
A group including amber, ruby, ivory, fluorite and opal photographed in ultra violet light. See 179 for the same group in white light

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