smoky quartz crystal cluster - teaching specimen from Novo Horizonte, Bahia, Brazil The vegetation was gradually compressed

The vegetation was gradually compressed to form peat

These were printed over a period from 1907 to 1954

Asbestiform tremolite from the McIlroy Mine

Since fulgurites are glass

complete with charger

smoky quartz crystal cluster - teaching specimen from Novo Horizonte, Bahia, Brazil The vegetation was gradually compressedTeaching 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