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| n-Gem meets Louboutin |
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| Johannes Vermeer – Girl with a Pearl Earring (c 1665-67) |
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| pearl evening (2014) |
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| pins |
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| Andradite (garnet) sample, Khazakstan |
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| garnet: crystal structure, Al, Si, Mg, Si and oxygen |
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| n-Gem: quartz manifestations |
silicon dioxide: SiO2
agate, onyx, amethyst, jasper, aventurine, tiger's eye, carnelian
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| layered tiger's eye quartz |
kyanite, Al2O3.SiO2. Kyanite's attractive colouring is due to the presence of Ti, V, Fe and Cr ions. Kyanite can also be coloured orange by Mn.
haematite, Fe2O3 crystal structure
An oxide of iron, haematite is the naturally occurring variety of iron III oxide. We also know it as the cosmetic rouge and as rust.
Here, the iron ions are represented by beige spheres Fe3+ surrounded by brown oxide ions O2-
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| natural haematite |
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| natural amethyst |
Amethyst is almost pure quartz, SiO2 which is coloured by Fe3+ ions via irradiation. Trace amounts of other transition elements lead to the reddening or bluing of the familiar violet transmission.
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| chrysoberyl, cymophane |
Cat's eye, a silicate of beryllium, BeAl2O4 is mined in Madagascar and Sri Lanka. Popular for its unusual colour changes, cymophane absorbs selectively in narrow bands of the spectrum dependent upon both the light source and the viewing angle, making it opalescent. Hence its common name.
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| black and ruby spinel |
Spinel, (Mg-Fe)(Al-Cr)2O4 found in Sri Lanka and Kenya, has been a valued gemstone throughout the ages. Many kingdoms include spinels in their crown Jewels including the Black Prince's Ruby embedded in the British Imperial State Crown.
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| Hayter: Queen Victoria (detail) |
Queen Victoria wearing her new coronation crown complete with the Black Prince's Ruby, a deep red spinel which is prominent at the front. From the George Hayter portrait of 1837, the year of her coronation.
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| the Russian Imperial Crown |
Popular with crown jewellers, another spinel takes pride of place. This time for the Russian Imperial Crown made for the coronation of Katerina the Great in 1762.
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| rhodonite in galena |
Rhodonite, a mix of calcium and magnesium silicates is coloured by manganese II and iron II ions:
(Fe2+ Mn2+ Mg Ca).SiO3 A lot of rhodonite is mined in the manganese mines of Sweden. The sample here is of rhodonite crystals embedded in lead II sulphide, PbS2 (galena). The latter is commonly known as fools gold due to its light yellow colouration.
