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Formula: NaFe3+3(Fe3+4Mg2)(Si6O18)(BO3)3(OH)3O
Cyclosilicate (ring silicate), tourmaline group,
boron-bearing mineral
Crystal system: Trigonal
Specific gravity: 3.26 measured, 3.33 calculated
Hardness: 7
Streak: Brown
Colour: Dark brown to brownish black
Common impurities: K,Mg,Al,Cu,Pb,Sn,Ti,V,H2O
Environments
Sedimentary environments
Metamorphic environments
Localities
At the type locality, the Cristalmayu valley, Cristalmayu, Cristalmayu subdistrict, Alto Chapare mining district, Chapare
Province, Cochabamba, Bolivia, povondraite occurs as black euhedral crystals which coat the country rock, which is
a schist composed of quartz,
K-feldspar, alkali amphibole and
muscovite. In addition, schorl is
present in varying amounts. The schists belong to a series of more or less
metamorphosed sedimentary rocks (including economically important magnesite).
The povondraite may be limited in its occurrence to younger fissures and cavities within the country rock, as is
the case with the original sample
(AM 64.945-948 as ferridravite).
Associated minerals include quartz,
K-feldspar, muscovite,
schorl, riebeckite and
magnesite
(HOM).
Povondraite from the Alto Chapare mining district -
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