SOUTH AMERICA
Tourmaline from Brazil
A tourmaline from the Pederneira claim in São José da Safira, Doce valley, Minas Gerais, Brazil. A gemstone and specimen mine in pegmatites. This is one of the worlds most important gem and specimen mines.
It was mined from about 1915, firstly for mica and was a major producer during WWII. Since then it has been mostly mined on a small scale for tourmaline and other minerals.
There are at least five distinct pegmatites worked in the mine. They are hosted by Precambrian quartzites, mica schists and amphibolites. The "amphibolites" are probably altered ultramafics, with olivine, pyroxene and garnet (pyrope).
The pegmatites are classically zoned granite pegmatites and from the border to core the zones are typically:
1. A thin mica rich selvage
2. The main border zone of granitic rock
3. The outer intermediate zone with muscovite rich granite
4. The inner intermediate zone, mostly K-feldspar
5. The central zone, of most I interest mineralogically, with coarse grained quartz and K-feldspar, and vughs with albite, tourmaline and spodumene
6. A quartz core
The 11 x 5 x 3cm. Tourmaline specimen in the picture shows blue to green colour with a deep pruple core. All faces are very glossy, the piece ist very showy in every position. The crystals are doble-terminated and the transperency is very high.
Photography: Martin Gruell
Web: www.viamineralia.com
Info source: www.mindat.org
CRYSTALS MINERALS GEMSTONES FOSSILS ROCKS
FONTE: Crystals Minerals Gemstones Fossils Rocks
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