Formula: NaBa3(Ca,U)Y(CO3)6.3H2O
Hydrated normal carbonate, mckelveyite group, barium- and yttrium- bearing mineral
Specific gravity: 3.25
Hardness: 3½ to 4
Colour: Yellow, orange-brown, grey, greenish brown, nearly black

Sedimentary environments
Hydrothermal environments

Mckelveyite-(Y) occurs in lacustrine deposits and in hydrothermal carbonate veins in dolostone (Webmin).


At the Khanneshin complex, Reg District, Helmand, Afghanistan, mckelveyite-(Y) is associated with dolomite, calkinsite-(Ce), carbocernaite, khanneshite and baryte (HOM).

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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