Geology and Minerals
Bristol Diamonds are quartz crystals found in geodes and geological rock formations which occur in dolomitic conglomerate in the Avon Gorge in Bristol, England. Their origin lies in geological processes of the Triassic period, about 250 to 200 million years ago. The Bristol Diamonds became popular novelties for visitors to the spa at Hotwells, Bristol, during the eighteenth and nineteenth centuries. Diarist John Evelyn and travel writer Celia Fiennes were amongst those who described them. In popular culture they became a synonym for something bright but worthless.
Diatom.
Geology of Iran.
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