Mckelveyite-(Y) is hydrated sodium, barium, yttrium, and uranium–containing carbonate mineral, with the chemical formula Ba3Na(Ca, U)Y(CO3)6·3H2O. It was first described in 1965 from deposits in the Green River Formation, Sweetwater County, Wyoming, and is named after Vincent Ellis McKelvey (1916–1985), a former director of the United States Geological Survey.
A related neodymium-rich mineral, mckelveyite-(Nd) has been described for an occurrence in the Vuoriyarvi alkaline-ultrabasic massif on the Kola Peninsula. However, the mineral has not been approved by the IMA.
General information
- Formula: NaCaBa3Y(CO3)6 · 3H2O
- Colour: Yellow, orange-brown, gray, greenish-brown, nearly black.
- Crystal System: Triclinic
- Density: 3.47 – 3.58, Average = 3.52
- Diaphaneity: Translucent to Opaque
- Streak: white
- Member of: Donnayite Group.
Properties
- Color: Lime-yellow, greenish-gray, reddish-brown, maybe black from contained organic material
- Crystal habit: Tabular, pyramidal
- Twinning: Threefold (pseudorhombohedral about {0001})
- Cleavage: Indistinct
- Mohs scale hardness: 3.5–4
- Luster: Vitreous, greasy, or dull
- Streak: White
- Diaphaneity: Transparent to opaque
- Specific gravity: 3.25
- Optical properties: Biaxial (-)
Occurrence – A rare mineral formed near trona beds in the Green River Formation (Wyoming, USA); in a differentiated alkalic massif (Khibiny massif, Kola Peninsula, Russia).
It occurs associate with trona layers in the Green River Formation of Wyoming and has been reported from an alkalic intrusive, the Khibiny Massif in the Kola Peninsula of Russia. It occurs in association with ewaldite, acmite, biotite, quartz, labuntsovite, searlesite, and leucosphenite in the Green River Formation. In the Khibiny Massif it occurs with ewaldite, belovite-(Ce), fluorite, nenadkevichite, ancylite-(Ce), synchysite-(Ce), kukharenkoite-(Y), burbankite, calcite, barite, and orthoclase. In the Khanneshin complex, Afghanistan it occurs with dolomite, calkinsite-(Ce), carbocernaite, khanneshite, and barite. It has also been reported from the Mont Saint-Hilaire intrusive complex in Quebec.
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