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Formula: Al(PO4).H2O
Hydrated phosphate, kieserite group
Crystal System: Monoclinic
Specific gravity: 2.923 calculated
Hardness: 3½ to 4
Streak: White
Colour: Light blue to white
Luminescence: No fluorescence under UV
Environments
Ermeloite is a new mineral, approved in 2021 and to date (October 2024) reported only from the type locality.
Localities
At the type locality, Mount Ermelo, Moaña, Pontevedra, Galicia, Spain,
granodiorite occurs consisting of
K-feldspar megacrystals, 3 to 4 cm in size, inside a matrix of fine to
medium grained plagioclase, quartz,
biotite and muscovite. Within this
granodiorite, decimetric to metric
pegmatitic dykes occur. The
pegmatite in which the ermeloite appears does not
present miarolitic cavities or textural zonation. The main rock-forming minerals include
quartz, microcline,
plagioclase, biotite,
muscovite and occasionally some
primary iron -
manganese phosphates. Hydrothermal alteration has produced the
secondary minerals
heterosite, trolleite,
crandallite, fluorapatite,
rockbridgeite–frondelite,
jahnsite-(CaMnMn), wardite,
burangaite, mitridatite,
phosphosiderite–strengite
and cacoxenite.
The sample of ermeloite studied is an ovoid nodule measuring 17.5 × 11.1 mm, embedded in
albitic plagioclase. The
ermeloite occurs as short-prismatic crystals with a maximum size of 0.05 mm. The colour ranges from light blue to
white and the streak is white. The crystals have a vitreous to pearly lustre and are transparent in thin fragments.
Ermeloite is brittle and shows a conchoidal fracture
(MM 88.412–420).
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