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Formula: CaMgSc(PO4)2(OH).4H2O
Phosphate, scandium-bearing mineral
Crystal System: Orthorhombic
Specific gravity: 2.43 measured, 2.44 calculated
Hardness: 4 to 4½
Streak: White
Colour: Grey to bright orange
Luminescence: Not fluorescent under UV
Solubility: Slowly soluble in 10% HCl
Environments
Although juonniite was approved in 1996, to date (December 2022) it has been reported only from the Kovdor
massif (2 different localities).
Localities
At the type locality, the Kovdor Zheleznyi mine, Kovdor Massif, Murmansk Oblast, Russia, juonniite occurs as a
rare mineral in cavities and contacts with ore minerals in metasomatically re-worked
calcite - phlogopite -
clinohumite - magnetite ores
in a calcite - dolomite
carbonatitic stockwork zone. Other associated minerals
include magnesite, bobierrite,
kovdorskite, hydrotalcite-2H,
hydrotalcite, apatite,
strontiowhitlockite,
pyrite, strontium-bearing
collinsite, rimkorolgite,
talc, baddeleyite,
zircon and gypsum.
The juonniite is found as spherulites, to 0.8 mm across, consisting of subparallel, commonly curved, plates up
to 12 mm across and 2 mm thick
(HOM, Mindat).
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