smoky quartz crystal cluster - teaching specimen from Novo Horizonte, Bahia, Brazil Asbestiform tremolite from the McIlroy

Asbestiform tremolite from the McIlroy Mine

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but the glass remained to become part of the sand

These were printed over a period from 1907 to 1954

In the 1920s and 1930s sand was barged from Long Beach

smoky quartz crystal cluster - teaching specimen from Novo Horizonte, Bahia, Brazil Asbestiform tremolite from the McIlroyTeaching 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