Golconda pegmatite field, Governador Valadares, Minas Gerais, Brazili

Regional Level Types
Golconda pegmatite field	Pegmatite Field
Governador Valadares	Municipality
Minas Gerais	State
Brazil	Country

See also https://www.mindat.org/loc-281837.html (Golconda, Governador Valadares) and https://www.mindat.org/loc-257186.html (Alto da Golconda mine, Golconda, Governador Valadares)

Safira pegmatite district, Eastern Brazilian pegmatite province.

Located about 25 km NW of downtown Governador Valadares.

Mine Information: The Golconda pegmatite was first mined for muscovite in 1908, first by open pit, and then in 1945 (again for muscovite) by underground extraction via an adit along the pegmatite's hanging wall. The mine name was not given.

Geology: Regionally, the geology comprises Archean metamorphics--mainly schists and gneisses--emplaced by sheet-like granite pegmatites varying in thickness from 3 to 11 meters and nearly horizontal. The host rock for the Golconda pegmatite itself is a mica schist, generally grading (west to east) from quartz-biotite-garnet to hornblende-rich. Intense deformations in the schists manifest as asymmetrical drag folds and the attendant faulting is thought to be the source of entry for the granitic fluids. The shearing of the country rock and introduction of granitic fluid were probably related to the same general diastrophism.

Grain size increases towards the centre of the pegmatite. Compositionally, the pegmatite exhibits an upper and lower border zone, a central zone, and a quartz-perthite zone in the western (and thickest) end of the pegmatite, above the central zone. The border and central zones are essentially K-feldspar, quartz, and muscovite. The greatest diversity of accessory minerals occurs in the more weathered central zone: beryl (morganite and aquamarine), tourmaline, garnet (spessartine), cassiterite, tantalite, microlite, spodumene, cookeite, and muscovite.

Irregular cavities hosting crystallization of the accessory minerals are most numerous in the central zone--especially towards the west.



Golconda is the name of a pegmatite field located approximately 20 km NE of Governador Valadares, where several pegmatites are famous for the production of outstanding mineral specimens; the most important pegmatites on the area are listed below:

Golconda I - also known as "Golconda of the Tourmalines"; in the 1960s it produced several hundreds of kilos of top-quality gem-grade elbaites (green and blue), and also light bicolour crystals (green-pink); associated minerals are quartz, albite, microcline, schorl, muscovite, cookeite, lepidolite; the mine was exhausted in the late 1960s and since then no production came from there.

Golconda II - also known as "Golconda of the Micas"; the mine was opened at the time of the Second World War to produce muscovite and clear quartz for industrial purposes; it was operated intermittently until the late 1990s; the most important minerals produced there are elbaite (blue and green), bertrandite (world-class clusters of crystals measuring up to 5 cm), fluorapatite (pink, purple, blue), quartz, albite, schorl, microcline, muscovite, cookeite, cassiterite, columbite-tantalite, hydroxylherderite

Faria mine (in the local language "Lavra do Faria") — it is the main producer of fluorapatites, as short prismatic millimetric crystals showing blue or purple colour, over quartz, albite, microcline, or muscovite matrix; bertrandite (always as millimetric white crystals) is a common accessory mineral, together with schorl, elbaite (dark green), rhodochrosite (iron-rich), todorokite, cassiterite, columbite-tantalite; beryl is found as coarse crystals embedded in the microcline on the intermediate zone of the pegmatite

Zé Pedra mine - ("Lavra Zé Pedra") — it produced large schorl crystals (up to 30 cm long) over albite (cleavelandite), muscovite and microcline matrix; in the mid 1990s it produced long and thin (up to 5 x 50 cm) curved schorl crystals; since 2008 it has been producing centimetric crystals of purple fluorapatite; large quartz crystals (up to 50 cm) have also been found, associated with albite, microcline, schorl and muscovite; millimetric white bertrandite crystals are also a common accessory mineral.

Escondido mine - ("Lavra do Escondido") — it produced large quartz crystals showing the so-called "cathedral habit"; long and thin dark-green elbaite crystals (up to 5 cm long) were found growing outside and/or inside the quartz crystals; in 2000 a few hundreds of clusters of centimetric pink fluorapatite crystals were found

Olhos D'Água mine - ("Lavra Olhos D'Água") — it became famous for the production, in the early 1970s, of clusters of beige-coloured, twinned hydroxylherderite crystals measuring up to 10 cm

Jacó mine - ("Lavra do Jacó") — it is a producer of industrial albite and microcline; occasionally coarse beryl crystals (blue, with some yield of cutting-rough) are found inside the intermediate zone; pockets in the central zone produce flattened morganite crystals, blue or green elbaite, quartz, albite, and muscovite crystals.

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