Quartz Collection (page 2)

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

Amethyst, baryte dioptase, rhodochrosite
Amethyst, purple crystals from India. Baryte, long yellow prisms from Cumbria. Dioptase, green lustrous crusts from Namibia. Rhodochrosite, pink crystals on quartz

Birthstone Series: Bloodstone
A specimen of the mineral bloodstone, a variety of quartz. (33974), from the Natural History Museum, London. Bloodstone is the birthstone for the month of March (along with Aquamarine)

Quartz variety amethyst

Chalcedony variety of quartz
A specimen of the mineral chalcedony, a variety of quarz, from the Haytor mine, Ilsington, Devon

Unakite

Citrine specimen

Citrine and amethyst are both varieties of quartz (silicon dioxide)

Agate
A cut and polished section of blue agate from Idar-Oberstein, Germany. Agate (silicon dioxide) is a cryptocrystalline quartz

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

Potentilla nivea L. snow cinquefoil
Sketch 2, Newfoundland Volumes. From a collection of original drawings and sketches by Georg Dionysius Ehret (1708-1770). Held in the Botany Library at the Natural History Museum, London

Yellow fluorite
A specimen of yellow fluorite (calcium fluoride) with white quartz (silicon dioxide) and brassy chalcopyrite, from Caradon Mines, Liskeard, Cornwall

Observing structure of rock
Looking at fresh granite under a microscope to study structure, granular composition can clearly be seen

Banded iron formation
3, 000 million year old specimen of banded iron-rich chert from the Murchison Goldfield, Western Australia. The banding derives from differing amounts and oxidation state of the iron composite

Sandstone is formed by loose grains of quartz compacted and cemented together

Quartz
A quartz specimen (silicon dioxide) from San Juan del Rey, Minas Gerias, Brazil

Quartzite

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)

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

The Mills of Gwynfynydd Mine, Wales, 1911
Photograph showing the mills of Gwynfynydd gold mine, near Carnarvon, 1911. These buildings were where quartz was crushed and washed to produce gold

Interior of a Gold Quartz Crushing Battery
Interior of a factory in the Thames gold-fields, New Zealand, where the process extracts gold from quartz

Brazil. Gold Washing. Foliated Gold with Quartz
Engraving of rock quartz with fern like striations of gold running through it

Gold mining at Johannesburg
An aerial photograph of gold mines in Johannesburg. The photograph was taken by Captain Spelterini on one of his balloon ascents

America. Photographs of California. Gold washing on the Yuba
Water was indispensible in the gold mining process and the water from the River Yuba was dammed and piped to wash away the sand and quartz from the gold particles

A City on Mercury
The inhabitants of Mercury are insectoid, and their techno- -logy is a superior form of that used by ants and bees on Earth : quartz crystals are used to build their cities

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