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Formula: CaZn(CO3)2
Anhydrous normal carbonate, dolomite group
Crystal System: Trigonal
Specific gravity: 3.45 measured, 3.445 calculated
Hardness: 3½ to 4
Streak: White
Colour: White, colourless
Solubility: Slowly dissolved by acids in cold, dilute hydrochloric acid, rapidly dissolved by warm acids
(AM 68.280-283)
Environments
Minrecordite occurs in the oxidation zone as a secondary
carbonate in carbonate-hosted zinc ores
(Webmin).
Localities
At the Navan Mine, County Meath, Ireland, minrecordite occurs in the wallrock of a carbonate-hosted
lead-zinc
orebody associated with sphalerite,
pyrite, marcasite, magnesian
calcite, dolomite,
calcite and quartz
(HOM)
At the type locality, the Tsumeb Mine, Oshikoto Region, Namibia, minrecordite occurs in a
dolostone-hosted hydrothermal polymetallic deposit
(Mindat, HOM).
It is found on dioptase, and with zincian
dolomite, duftite and
malachite needles in the oxidation zone; manganese-rich minrecordite
is also found here with ochre (earthy minerals) inclusions, and associated with
cerussite and calcite
(AM 68.42-45, Dana, HOM)
Alteration
Minrecordite forms at the type locality at low temperatures under oxidising conditions. Thermochemical
calculations indicate that pure end member minrecordite would be unstable under ambient atmospheric conditions, and
in nature some magnesium (from dolomite) remains unchanged, whilst most of it
is replaced by zinc
(AM 68.42-45, R&M 95.1.42-45)
The paragenetic sequenceis as follows:
1. calcite, zincian
dolomite and
duftite
2. dioptase I
3. magnesian minrecordite, rarely associated with cerussite and
calcite
4. minrecordite
5. dioptase II
(Minrec 13.131-136)
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