A very hot environment.


http://news.nationalgeographic.com/news ... tals-cave/
http://news.nationalgeographic.com/news ... als_2.html
http://ngm.nationalgeographic.com/2008/ ... /shea-text
http://www.canyonsworldwide.com/crystals/index.html
http://channel.nationalgeographic.com/e ... 9/Overview
http://www.crystalinks.com/mexicocrystals.html
