Fluorite

Last time when I showed my pink topaz from Pakistan and mentioned that fromed from a silicate undersaturated environment. Here is an example of outlier, pink topaz on quartz associate with magnesite.

This specimen from Brumado, Bahia, Brazil, with prominent basement Rocks that are Precambrian in age and consist predominantly of gneisses, schists, and amphibolites. A metamorphosed sequence, comprising a lower unit of dolomite and an upper unit of quartzite, overlies the basement rocks. No case studies have done on topaz formation in this area, however, due to the lack of fluorite, it is possible Ca lose during an earlier hydrothermal alteration event, or, the origin has low Ca that may also be buffered by forming invite during the late stage rather than fluorite. The source of Mn (which makes topaz pinkish) could be carried from sediment origin metamorphic rocks and Al, F from the amphibolite from the basement by hydrothermal fluids.

This topaz is just a quick example to show the diverse and complexity of the geology, so many rocks and processes are required to end up with a little specimen in our collection.

Pink Topaz on Quartz with Magnesite, Brumado, Bahia, Brazil

1.8cm, Jingnan (Tom) Zhang Coll & Photo