smoky quartz crystal cluster - teaching specimen from Novo Horizonte, Bahia, Brazil Click > here < for

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The oldest radiolarian fossils in the cherts lived about 200 million years ago

Asbestiform tremolite from the McIlroy Mine

but the glass remained to become part of the sand

smoky quartz crystal cluster - teaching specimen from Novo Horizonte, Bahia, Brazil Click > here < forTeaching smoky quartz cluster from Municpio Novo Horizonte, Bahia, Brazil. This area is famous for smoky quartz, often with rutile inclusions in the crystals. Smoky quartz forms from natural gamma radiation released by surrounding rocks. The radiation causes aluminum atoms, which replace silicon atoms in the crystal lattice, to transfer an electron to a neighboring positively charged ion, often Li+, forming an aluminum metal color center that darkens