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Formula: MnCe(Fe3+AlMn2+)(Si2O7)(SiO4)O(OH)
Sorosilicate (Si2O7 groups), allanite group,
epidote supergroup,
manganese- and cerium-
bearing mineral
Crystal System: Monoclinic
Specific gravity: 4.321 calculated for the empirical formula
Hardness: 6½ to 7
Streak: Light brown
Colour: Dark brown
Luminescence: Not fluorescent in short wave or long wave UV
Environments
Ferriandrosite-(Ce) is a new mineral, approved in 2023.
Localities
At the type locality, the Július manganese occurrence, Betliar, Rožňava District, Košice Region, Slovakia, samples
with ferriandrosite-(Ce) were collected from the dump of the main exploration adit.
At this occurrence, small bodies and lenses of metamorphosed carbonate–silicate
manganese ore mineralisation are hosted in Lower Palaeozoic (541 to 252
million years ago) black phyllites and
lydites, metamorphosed in
greenschist facies conditions.
Ferriandrosite-(Ce) was discovered in a large block of
rhodochrosite –
spessartine – pyroxmangite
– magnetite ore, cut by abundant younger veinlets consisting mainly of
coarse crystalline pyroxmangite and
spessartine, with minor amounts of
quartz, rhodochrosite,
baryte and
pyrosmalite-(Mn). It occurs rarely as aggregates embedded in
pyroxmangite –
spessartine veinlets, together with
rhodochrosite, quartz,
baryte and pyrosmalite-(Mn).
Ferriandrosite-(Ce) occurs as subhedral grains and polycrystalline aggregates up to 0.3 mm in size, enclosed
in pyroxmangite –
spessartine matrix
(MM 87.6.887-895)
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