Oxide Mineral Collection (page 2)

Wood tin, variety of cassiterite
Dark-brown banded aggregates of cassiterite intergrown with white quartz and black tourmaline. Cassiterite comprises of (tin oxide). This polished specimen is from West Kitty mine, St. Agnes, Cornwall

Trechmannite
A red crystal of trechmannite comprised of (silver arsenic sulphide). A specimen from the collections of the Natural History Museum, London

Goethite comprises of hydrated iron oxide. Picture shows radiating bands within the disc-shaped crystals. This specimen is displayed at the Natural History Museum, London

Pleochroism in an iolite cut stone
This iolite (magnesium aluminium silicate) is displaying pleochroism, a varied colour effect as the gem is turned. See also 3960

Spinel crystal and cut stone
Spinel (magnesium aluminium oxide) crystal from Ruby Mines, Mogok, Burma with spinel cut stone from Sri Lanka. Spinel is found in a red colour and has been previously mistaken for ruby

Anatase
A brown to black single tetragonal crystal of anatase (titanium oxide). Anatase is a polymorph of rutile and brookite, meaning they carry the same chemistry, but with a different structure

Many colours of corundum
Ruby and sapphire cut corundum stones viewed through their pavilions. Corundum is the second hardest natural mineral known

Rubies and sapphires
Crystals of ruby from Burma which is the red variety of corundum (aluminium oxide). The other variety is sapphire, this specimen is from Kashmir. The lower left specimen is the Edwardes Ruby

Braunite is a native oxide of manganese. Its crystals are dark brownish black in colour. Specimen from the Natural History Museum, London

Ruby and sapphire gravel
Ruby and sapphire fragments from gem gravels seen on a background of slate. Ruby and sapphire are both varieties of the mineral corundum (aluminium oxide)

Tiger s-eye and Hawk s-eye
Formed when blue crocidolite asbestos is replaced by quartz. Hawk s-eye retains the original colour while tiger s-eye contains a residue of iron oxide

Zincite comprises of (zinc oxide). It is an important ore of zinc, and almost exclusive to one mining locality in New Jersey, U.S.A. Specimen from the Natural History Museum, London

Tenorite is comprised of (copper oxide). It is found as grey to black metallic crystals and as a by-product of lava flows. Fibrous specimen from the Natural History Museum, London

Franklinite, fluorescing
Ore of zinc fluorescing under ultra violet radiation: calcite - pink; willemite - green; zincite - blue; franklinite - black. See image number 388 for white light view

Gemstone series: sapphire
Sapphire, the blue variety of the mineral corundum (aluminium oxide). Sapphire can be found in a number of different colours. Specimen at the Natural History Museum, London

Birthstone Series: Ruby

Chrysis rudii, ruby-tailed wasp
An illustration of a ruby-tailed wasp (Chrysis rudii)

Cassiterite, sparable tin
Dark-brown slender lustrous prisms of cassiterite (tin oxide) on brownish siderite and dark-green chlorite. Specimen from the Dolcoath mine, Camborne, Cornwall

Plate 99, from Mineralogie
Various gemstone varieties including diamond, ruby, sapphire, spinel and Topaz. From Recuille complet de Mineralogie vol.3 (1790) by F.L. Swebach Desfontaines

Sweetite
A Specimen from the collections held at the Natural History Museum, London from Milltown, Ashover, Derbyshire

Hematite tumblestone

Hematite group
A group of hematite

Star rubies and sapphires
Star stones of ruby and sapphire, both are varieties of the mineral corundum (aluminium oxide). Ruby always appears in red where as sapphire comes in a variety of colours

Ruby and Sapphire cut stones

Alexandrite
A twinned alexandrite crystal. Alexandrite is a variety of chrysoberyl (beryllium aluminum oxide) and is named after the former Czar of Russia, Alexander II

Ruby
A six-rayed star ruby. Ruby is the red variety of the mineral corundum (aluminium oxide)

Sapphire
A six-rayed star blue sapphire. Sapphires derives from the corundum mineral group which is the second hardest group known

Chromite (iron chromium oxide) is the ore of chromium and has an attractive shiny surface. It is used in the manufacture of stainless steel and in metallic paints

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

Brookite
A specimen of the mineral brookite (titanium oxide) from Tremadoc wales. Brookite is a polymorph, it has the same chemical composition as rutile and anatase

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

Rutile
A specimen of the mineral rutile (titanium oxide) which is a major ore of the metal titanium. This specimen is from Graves Mountain, Lincoln County, Georgia. USA

Hematite
Iridescent crystalline mass of hematite (iron oxide) from Rio Marina, Elba. Specimen from the collections of the Natural History Museum, London

Baryte crystals
Yellow prisms of the minreal baryte (BaSO4) on hematite (iron oxide) from Dalmellington Mine, Frizington, Cumbria

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)

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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