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

Metamorphic environments

Ferriandrosite-(Ce) is a new mineral, approved in 2023.


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 rhodochrositespessartinepyroxmangitemagnetite 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 pyroxmangitespessartine 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 pyroxmangitespessartine matrix (MM 87.6.887-895)

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