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Formula: Ca2(☐,Mn)2(Fe3+,Mn,Mg)4Be4(PO4)6(OH)6.4H2O
Hydrated phosphate, roscherite group,
manganese- and
beryllium- bearing mineral
Crystal System: Monoclinic
Specific gravity: 2.88 measured, 2.859 calculated
Hardness: 4½
Streak: Orange-brown
Colour: Reddish brown
Luminescence: Not fluorescent under UV
Solubility: No gas evolution was observed with hydrochloric acid
Environments
Localities
At the type locality, the Sapucaia mine, Sapucaia do Norte, Galiléia, Minas Gerais, Brazil, ruifrancoite occurs
as a late vug-filling product in a zoned, LCT-type (lithium,
cesium, tantalum)
granitic
pegmatite. It crystallised on
albite and muscovite and occurs in
close association with cyrilovite and
meurigite. In the core zone, essentially composed of
quartz, perthite,
muscovite and beryl, there is an
irregular body of triphylite weighing several hundred tonnes, which was
partially altered by hydrothermal fluids and later, as a result of weathering. An assemblage of rare phosphates
resulted, six of which have been described as new mineral species: frondelite,
faheyite, moraesite,
barbosalite, tavorite and
arrojadite-(PbFe).
There are three principal assemblages corresponding to separate geochemical environments:
(1) the triphylite assemblage, as fracture fillings and replacements in
massive triphylite
(2) the frondelite assemblage, consisting of residual phosphates enclosed
by frondelite, results of a massive replacement of that mineral, and
minerals on walls of vugs in frondelite
(3) the silicate assemblage, formed by secondary crusts on
altered albite, products of the alteration of
beryl, and replacement and vug fillings in
muscovite.
Ruifrancoite occurs in the third assemblage as needles and laths with a thickness of 1 to 2 mm and a length of
about 100 mm, in fan-shaped reddish brown botryoidal arrangements
(CM 45.1263-1273).
Ruifrancoite from Sapucaia - Image
At Chandlers Mill Quarry, Newport, Sullivan County, New Hampshire, USA, ruifrancoite has been provisionally
identified
(R&M 97.3.231).
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