Formula: (Pb,☐)2Ta2O6[☐,(OH),O]
Oxide, microlite group, tantalum-bearing mineral
Specific gravity: 7.310 to 7.832 measured, 7.122 calculated
Hardness: 6
Streak: White
Colour: Yellowish brown
Luminescence: No fluorescence under UV


Kenoplumbomicrolite was approved by IMA as a valid, new species in 2016. To date it has been reported only from the type locality.


At the type locality, Ploskaya Mt, Western Keivy Massif, Keivy Mountains, Lovozersky District, Murmansk Oblast, Russia, kenoplumbomicrolite occurs in an amazonite pegmatite. It forms yellowish brown octahedral, cuboctahedral and massive crystals, up to 20 cm. Attempts to measure density were affected by the ubiquitous presence of uraninite inclusions (MM 82.1049-1055).
The vein was confined to the contact between gneiss and schist. The vein contact zone consists of fine-grained albite and is succeeded nearer the centre by an indistinct zone of amazonite blocks up to 2.5 m in size and partly replaced by albite. The quartz core has galena pockets up to 0.4 m, coarse biotite flakes and cleavelandite aggregates. Other associated minerals are zinnwaldite, anglesite, bastnäsite-(Ce), bismite, bismuth, bismuthinite, bismutite, cassiterite, caysichite-(Y), churchite-(Y), columbite-(Mn), emplectite, fergusonite-(Y), fluorite, gadolinite-(Y), gahnite, galena, hingganite-(Y), hingganite-(Yb), kainosite-(Y), kamphaugite-(Y), kasolite, keiviite-(Y), keiviite-(Yb), kuliokite-(Y), lanarkite, leadhillite, löllingite, monazite-(Ce), pyromorphite, scotlandite, sillénite, sphalerite, tengerite-(Y), thalénite-(Y), thorite, uraninite, vyuntspakhkite-(Y), wulfenite, xenotime-(Y), xenotime-(Yb) and zavaritskite. The mineral “plumbomicrolite” was identified in this vein in 1975, but according to the IMA-approved rules for nomenclature the name “plumbomicrolite” must be preceded by the prefix “keno,” which indicates that the Y site is dominantly vacant (AM 106.1189).

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