TOURMALINITE SILVER ORE
Tourmalinite is an uncommon metamorphic rock dominated by finely crystalline tourmaline.
The photos below are of a black-colored, lineated tourmalinite from the Broken
Hill Block of New South Wales, Australia. The tourmalinite has been
broken, folded, and intruded by an irregularly-shaped hydrothermal vein mass of
argentiferous galena ((Pb,Ag)S - lead silver sulfide). The silver
content is high enough to make this rock a silver ore. The rock is waaaay
more awesome is person than the photos suggest. ItÕs one of my favorite
rocks.
Locality:
subsurface sample from the Umberumberka Mine (~31¡ 53Õ 37Ó South, ~141¡ 11Õ 26Ó
East), 2-3 km west of the town of Silverton, WNW of Broken Hill, Broken Hill
Block, far-western New South Wales, southeastern Australia.
Stratigraphy: Umberumberka Lode (ÒMain LodeÓ) intruding the Willyama Supergroup,
upper Paleoproterozoic.
Metamorphic age: high-grade metamorphic events affected rocks of this
area at ~1660 m.y. and ~1599-1600 m.y.
Age of hydrothermal Ag-galena vein emplacement: possibly at ~510-520 m.y., Early to Middle Cambrian.
Tourmalinite (black) with argentiferous galena (silvery-white) & minor
chalcopyrite and pyrite (both brassy gold). Field of view ~7.2 cm across.
Lineated tourmalinite (black) with argentiferous galena (silvery-white)
& minor chalcopyrite and pyrite (both brassy gold). Field of view
~3.6 cm across.
Argentiferous galena, (Pb,Ag)S.
Lineated tourmalinite (black) with argentiferous galena (silvery-white)
& minor chalcopyrite and pyrite (both brassy gold). Field of view
~2.6 cm across.
Most info. summarized from various items of Broken
Hill Block geologic literature.
Collected
& generously donated by Molly Tannian.