Orthobrannerite

orthobrannerite

biotite

pyroxene

lamprophyre

Images

Formula: U4+U6+Ti4O12(OH)2
Multiple oxide, forms a series with thorutite, uranium- and titanium- bearing mineral
Crystal System: Orthorhombic
Hardness: 5½
Streak: Dark brown to black
Colour: Black
Luminescence: Not fluorescent under UV
Solubility: Not attacked by hydrochloric and sulphuric acid, but dissolves in warm sulphuric acid and H3PO4
Strongly RADIOACTIVE
Environments

Igneous environments

Orthobrannerite was first found in the weathering residue of a biotite pyroxene syenite in Yunnan, China. It was later also identified, from its heat-treatment product, in an alkalic lamprophyre in Szechuan, China.
The natural mineral is fully metamict and is black with dark brown to black streak, adamantine lustre, and white under reflected light with a reddish brown internal reflection. After heating to 1OOO°C the mineral becomes brownish-green on thin edges, giving a brownish-yellow streak with a green tint (AM 64.656).

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