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Formula: Zn3(CO3)(OH)4
Carbonate
Crystal System: Monoclinic
Specific gravity: 3.93 to 4.09 measured, 4.11 calculated
Hardness: 2 to 2½
Streak: White
Colour: White, colourless
Solubility: Readily soluble in 1:10 acids (Dana)
Environments
Brianyoungite is a secondary post-mining mineral in
limestone-hosted oxidised
lead-zinc ores
(Webmin).
Localities
At the type locality, the Brownley Hill mine, Alston Moor, Eden, Cumbria, England, UK, rosettes of brianyoungite
are associated with gypsum on rubbly
limestone, or black shaly
coatings on limestone, within the oxidised zone. Apart from oxidising
pyrite with accompanying goethite
and iron staining, the only other minerals noted are ktenasite
and smithsonite. Brianyoungite developed as individual rosettes on the
surface of specimens or within cavities, and as coalescences forming thin surface layers. Additionally, it may be
encapsulated by gypsum
(MM 57.665-670, AM 79.1009). It is almost certainly formed by post-mining oxidation
(Minrec 31.3.244).
At the Smallcleugh Mine, Nenthead, Alston Moor, Eden, Cumbria, England, UK, brianyoungite occurs with
sphalerite, calcite,
quartz, pyrite,
fluorite and hydrozincite
(AESS).
At the Tynebottom mine, Alston Moor, Eden, Cumbria, England, UK, Small crusts of minute crystals of brianyoungite
have been found in the carbonate field of four specimens, mostly in intimate association with crusts of
hydrozincite. On three of the specimens,
gypsum was in close association
(JRS 10.3-8).
At the Elgar Mine, Bontgoch, Ceredigion, Wales, UK, brianyoungite is extremely rare, but has been found as as
minute rosettes to 0.3 mm of crystals coating a single specimen of iron-stained quartz
and galena from the deep adit dumps
(MW).
At Frongoch Mine, Devil's Bridge, Ceredigion, Wales, UK, spherulitic aggregates of crystals of brianyoungite up to
0.5 mm across have been found in a galena-rich matrix
(MW).
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