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Formula: ZnAs3+2O4
Normal arsenite
Crystal System: Monoclinic
Specific gravity: 4.3 measured, 4.61 calculated
Hardness: 1½ to 2
Streak: White
Colour: Colourless to brown
Environments
Leiteite is a rare arsenite that occurs almost exclusively at its type locality, the Tsumeb Mine,
Oshikoto Region, Namibia. Other reported
occurrences in Germany and Austria are in slag deposits, and are of anthropogenic origin
(R&M 92.3.264-267).
At the type locality leiteite occurs with other zinc and
arsenic-bearing minerals in an oxidised zone in a
dolostone-hosted hydrothermal polymetallic ore deposit
(HOM).
Associated minerals
include chalcocite, tennantite,
reinerite,
schneiderhöhnite, zincian
stottite, zincroselite,
tsumcorite, stranskiite,
legrandite and smithsonite
(HOM, AM 62.1259-1260).
Its association with the arsenite mineral schneiderhöhnite, which
is considered to
have formed at 40oC, would indicate a low temperature origin for leiteite
(AM72.629-632).
In arsenites arsenic occurs in its
intermediate As(III) oxidation state, so it is likely that these levels had a reducing oxygen-deficient atmosphere
during the
crystallisation of these minerals
(R&M 92.3.264).
In the type assemblage, leiteite is associated with smithsonite and
schneiderhöhnite in
chalcocite -
tennantite ore
(R&M 92.3.264).
Locations of further occurrences of leiteite at Tsumeb include:
The 29 and 30 levels, where leiteite was associated with legrandite,
reinerite, stottite,
stranskiite and zincroselite.
The third oxidation zone, mainly on the 44 and 45 levels, where leiteite was found in relatively
large quantities. The first mineral to
crystallise from the solution was leiteite, followed by reinerite,
then legrandite, followed by
adamite,
then paradamite and lastly
smithsonite.
In one pocket on the 44 level leiteite was associated with bunches of
ludlockite needles.
Another pocket on the 44 level contained the largest leiteite known. The assemblage of this pocket differed
from the other finds and
included adamite, köttigite and
ianbruceite
(R&M 92.3.264-267).
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