Thoreaulite

Formula: SnTa2O6

Origin of name: for Jacques Thoreau (1886-1971), Belgian mineralogist, University of Louvain, Belgium, authority on Congolese (Zairian) mineral occurrences.

 

Crystal system: Monoclinic

Crystal class: 2/m

Twinning: On {010} as composition face, lamellar

Unit cell: a = 17.14, b = 4.865, c = 5.548, β = 91°

 

Colour: brown, yellow brown, resin brown, red when altered

Diaphaneity: Opaque to translucent in thin fragments

Luster: Resinous to adamantine on the cleavage

Habit: Crystals short prismatic, subhedral, lamellar twinning, masses to 10 cm

Hardness: 5.5 to 6

Specific gravity: 7.6 to 7.9

Cleavage: 2; {100} perfect, {011} imperfect

Tenacity: 

Streak: Brown to yellow, slightly greenish

 

Synonyms/varieties:

 

Comments: Series with foordite.  Secondary mineral in cassiterite-bearing rocks

 

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