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Formula: NaBa3(Ca,U)Y(CO3)6.3H2O
Hydrated normal carbonate, mckelveyite group,
barium- and
yttrium- bearing mineral
Crystal System: Triclinic
Specific gravity: 3.25 measured, 3.37 calculated
Hardness: 3½ to 4
Colour: Yellow, orange-brown, grey, greenish brown, nearly black
Environments
Carbonatites
Sedimentary environments
Hydrothermal environments
Mckelveyite-(Y) occurs in lacustrine deposits and in hydrothermal carbonate veins in
dolostone (Webmin).
Localities
At the Khanneshin complex, Reg District, Helmand, Afghanistan, mckelveyite-(Y) is associated with
dolomite, calkinsite-(Ce),
carbocernaite, khanneshite
and baryte
(HOM).
At the IMI Fabi Mine, Mt. Motta, Lanzada, Sondrio Province, Lombardy, Italy, a new polytype of mckelveyite-(Y)
was found hosted in hydrothermal carbonate veins that are intercalated with
dolomite veins and ultrabasic
rocks associated with serpentinite. The associated minerals
include anatase, brookite,
brucite, calcite,
dolomite, ilmenite,
lindsleyite, magnesite,
magnetite, pyrite,
quartz, redledgeite and
rutile.
Crystals of mckelveyite-(Y)-2M are pseudopyramidal, up to 4 mm in length and have a distinct trigonal
character. Crystals are photosensitive going from pale pink to almost colourless on exposure to sunlight; the colour
reappears when they are returned to a dark environment
(AM 93.1945-1946).
At the Khibiny Massif, Murmansk Oblast, Russia, mckelveyite-(Y) forms barrel-shaped pseudohexagonal crystals up
to 3 cm with sector zoning and disk-shaped pseudo-rhombohedral crystals up to 3 mm across. It occurs in an
aegirine-feldspar-natrolite-calcite vein in
syenite and in a
siderite-ankerite-natrolite
vein in carbonatised foyaite, as well as in cataclastic
(pertaining to
clastic rocks, the fragments of which have been produced by the fracture of preexisting rocks by Earth stresses -
(Mindat)) albitite in the contact zone of the massif.
Associated minerals include ewaldite,
belovite-(Ce), fluorite,
nenadkevichite,
ancylite-(Ce),
synchysite-(Ce),
kukharenkoite-(Y),
burbankite, calcite,
baryte and orthoclase
(AM 78.236-237, HOM).
At the Sallanlatvi Massif, Northern Karelia, Murmansk Oblast, Russia, mckelveyite-(Y) forms platy aggregates in
solution cavities in carbonatite. Associated minerals
include
sphalerite, galena,
pyrite, baryte,
strontianite, fluorite,
ancylite, ewaldite,
cordylite, donnayite-(Y),
vinogradovite, catapleiite,
epididymite,
orthoclase, zircon and
burbankite
(AM 78.236-237).
The type localityis Diamond Alkali Daco No. 3, Sweetwater County, Wyoming, USA. In studying waste residues from soda
ash
production in the area tiny green crystals have occasionally been found, but not enough for analysis initially. Enough
material for chemical analysis finally became available in 1959 when mckelveyite-(Y) was found in relative
abundance in a few inches of core taken at a depth of 1576 feet from the Diamond Alkali Daco No. 3.
Although these crystals were usually black rather than green in colour, and varied somewhat in habit from the crystals
found earlier, the evidence indicates that the colour differences are due merely to the presence of contaminants
(AM 50.593-612).
Associated minerals include ewaldite,
aegirine, biotite,
quartz, labuntsovite,
searlesite and leucosphenite
(HOM).
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