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Formula: GeO2
Oxide of germanium, trigonal
paramorph of tetragonal argutite
Crystal System: Trigonal
Specific gravity: 4.18 calculated for the empirical formula and 4.30 for the ideal formula.
Streak: White
Colour: White to brownish
Luminescence: Not fluorescent under UV
Solubility: Slightly soluble in water, soluble in hydrochloric acid, HF and NaOH.
Melting point: 1116°C
Environments
Pertoldite is a new mineral, approved in 2021 and to date (January 2024) reported only from the type locality.
Localities
At the type locality, the Kateřina Coal Mine, Radvanice, Trutnov District, Hradec Králové Region, Czech Republic,
pertoldite occurs as aggregates resembling cotton tufts, up to 1 mm in size, composed of acicular crystals up
to about 1 μm thick and up to 1 mm in length. Individual crystals are distorted, resembling textile fibres.
Pertoldite is formed by direct crystallisation from hot (400 to 500°C) gasses containing Cl and F as
transporting agents at a depth of 40 to 60 cm under the surface of a burning coal mine dump. Associated minerals include
stibnite, greenockite,
galena, bismuth-bearing
antimony and bismuth
(Mindat).
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