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Formula: Be2(PO4)(OH).4H2O
Hydrated phosphate containing hydroxyl, beryllium-bearing mineral
Crystal System: Monoclinic
Specific gravity: 1.805 measured, 1.806 calculated
Streak: White
Colour: White
Solubility: Soluble in 1:10 acids (Dana)
Environments:
Moraesite is a rare late-stage hydrothermal mineral in complex zoned
granite
pegmatites. Associated minerals include
beryl,
beryllonite,
hydroxylherderite,
frondelite, triphylite,
apatite and muscovite
(HOM).
Localities
The type locality is the Sapucaia mine, Sapucaia do Norte, Galiléia, Minas Gerais, Brazil. Phosphate minerals are
most abundant in the
central part of the granite
pegmatite here; they are associated with
quartz, beryl,
perthite and muscovite. Large
masses of
triphylite and heterosite up
to several tons in weight
are the principal phosphate minerals. In addition to moraesite, other phosphate minerals include
frondelite, faheyite,
hureaulite, childrenite,
apatite, roscherite,
vivianite and variscite.
Moraesite occurs on the
walls of vugs that have developed in or adjacent to beryl, and on surfaces of
albite, quartz and
muscovite. Growths of moraesite frequently occur on the surfaces of
frondelite and contain unaltered fragments of
beryl
(AM 38.1126-1133).
At the Humaita pegmatite, Itinga, Minas Gerais, Brazil, moraesite occurs in the oxidation zone with
beryl, albite,
quartz, muscovite and
frondelite
(Dana).
At the Emmons pegmatite, Greenwood, Oxford county, Maine, USA, moraesite is associated with
hydroxylherderite, beryl
and
fluorapatite. The Emmons pegmatite is an example of a highly evolved
boron-lithium-cesium-tantalum
enriched pegmatite
(R&M 94.6.512).
Pink masses of väyrynenite occur at the area of interaction of
lithiophilite with altered
beryl. Beryllonite,
roscherite, moraesite and
hydroxylherderite also occur in this assemblage
(CM 57.733-734).
In New Hampshire, USA, moraesite is a rare late-stage hydrothermal mineral found in complex, zoned
pegmatites. It occurs as groups of white acicular crystals,
cottonlike aggregates or felted masses. The Palermo No. 1 mine in Groton and the E. E. Smith mine in Alexandria have
produced attractive specimens of moraesite with individual crystals only a few millimetres in length, but some
masses can be up to 3 cm
(R&M 97.3.228-229).
At the Chickering Mine, Walpole, Cheshire county, New Hampshire, USA, moraesite is uncommon, but when found,
it
generally occurs in
minute crystalline voids of quartz and
siderite
(R&M 90.5.419). It occurs as bright white silky fibres in flat sprays and mats to 0.8 mm across
(R&M 97.3.228-229).
At the Keyes Mica Quarries, Orange, Grafton County, New Hampshire, USA, the
pegmatites are
beryl-type
rare-element (RE) pegmatites.
The Number 1 mine exposed a pegmatite that shows the most
complex zonation and diverse mineralogy of any of the Keyes
pegmatites. Six zones are distinguished, as follows,
proceeding
inward from the margins of the pegmatite:
(1) quartz-muscovite-plagioclase
border zone, 2.5 to 30.5 cm thick
(2) plagioclase-quartz-muscovite
wall zone, 0.3 to 2.4 metres thick
(3) plagioclase-quartz-perthite-biotite
outer intermediate zone, 0.3 to 5.2 metres thick, with lesser muscovite
(4) quartz-plagioclase-muscovite
middle intermediate zone, 15.2 to 61.0 cm thick
(5) perthite-quartz inner intermediate zone, 0.9 to 4.6 meters thick
(6) quartz core, 1.5 to 3.0 metres across
The inner and outer intermediate zones contained perthite crystals up to
1.2 meters in size that were altered to vuggy
albite-muscovite with
fluorapatite crystals. This unit presumably was the source of the
albite, muscovite,
fluorapatite, quartz and other
crystallised minerals found in pieces of vuggy albite
rock on the dumps next to the mine.
The middle intermediate zone produced sheet mica with accessory minerals including
tourmaline, graftonite,
triphylite, vivianite,
pyrite, pyrrhotite, and
beryl crystals to 30.5 cm long and 12.7 cm across.
Moraesite was identified in a specimen as matted white fibres associated with botryoidal microsized
hydroxylherderite and
lazulite-scorzalite
(R&M 97.4.321).
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