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Formula:
(Ca,REE)19Fe3+Al4(Mg,Al,Fe3+)8Si18O68(OH,O)10
Sorosilicate (Si2O7 groups), vesuvianite group,
REE (rare earth element)-bearing mineral
Crystal System: Tetragonal
Specific gravity: 3.53 measured, 3.547 calculated for the empirical formula
Hardness: 6
Colour: Dark brownish red
Luminescence: Notfluorescent under short wave or long wave UV
Environments
Sedimentary environments
Metamorphic environments
Hydrothermal environments
Milanriederite is a relatively new mineral, approved in 2018 and to date (March 2024) reported only from the
type locality.
Localities
At the type locality, the Kombat Mine, Kombat, Otavi Constituency, Otjozondjupa Region, Namibia, milanriederite
occurs in a
jacobsite–hausmannite ore. The
mineral assemblage that contains milanriederite was formed by hydrothermal and metasomatic replacement and
fracture-filling of dolostones of Upper Proterozoic age (1800 to 570
million years ago) by polymineralic aggregates consisting of manganese-rich
spinels, calcite,
dolomite and baryte, as well as
various subordinate components including several lead oxychlorides. The estimated temperature of milanriederite
crystallisation is in the range 400 to 550oC.
Milanriederite occurs as dark brownish red dipyramidal crystals up to 3 mm across embedded in granular
baryte – calcite –
jacobsite – hausmannite
aggregates with minor glaucochroite and
native copper.
It is assumed that milanriederite is the earliest mineral in this association, and
native copper came later
(EJM 31.3.637-646)
Milanriederite from Kombat
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