Orlovite

orlovite

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Formula: KLi2Ti(Si4O10)(OF)
Phyllosilicate (sheet silicate), trioctahedral mica group, mica group, lithium- and titanium- bearing mineral
Crystal System: Monoclinic
Specific gravity: 2.91 measured, 2.014 calculated
Hardness: 2 to 3
Streak: White
Colour: Colourless to white
Luminescence: Fluoresces bright yellow under short wave UV, but does not fluoresce under long wave UV
Environments

Pegmatites

Orlovite was approved in 2009 but to date (April 2025) it has been reported only from the type locality.

Localities

At the type locality, the Dara-i-Pioz Massif, Districts of Republican Subordination, Tajikistan, orlovite was discovered in samples collected on a moraine of the Darai-Pioz glacier. One of the characteristic features of the massif is the wide variety of mica minerals present, including muscovite, annite, tainiolite, polylithionite, sokolovaite and orlovite. Orlovite is the titanium analogue of polylithionite, and it is the first completely titanian mica from the mica group. It occurs in a rock consisting mainly of quartz with several rare accessory minerals. The rock is composed of middle to coarse-grained aggregates of quartz of icy appearance. The appearance of these Si-rich rocks is very characteristic because of the presence of idiomorphic black crystals of aegirine with brilliant facets, large violet-pink plates of sogdianite, red-brown translucent lenticular crystals of stillwellite-(Се), poorly-bounded crystals of pale yellow-pink reedmergnerite, green elongated prismatic crystals of turkestanite and large crystals of polylithionite. In addition, galena, calcite, neptunite, sugilite, pyrochlore, minerals of the eudialyte group, tadzhikite, baratovite, native bismuth, sphalerite, fluorite, fluorapatite, fluorapophyllite, sokolovaite, kapitsaite-(Y), pekovite, zeravshanite and faizievite occurs in this rock. A characteristic feature of this essentially quartz rock is the presence of brown polymineral aggregates (up to 25 cm in size) consisting of pectolite, quartz, fluorite, aegirine, polylithionite and other minerals.
Segregations of orlovite occur mainly in intergrowth with pectolite, quartz, baratovite, neptunite, leucosphenite, zeravshanite, faizievite and pyrochlore. Orlovite forms lamellar, colourless grains up to 2 mm in size that appear white in aggregates (New Data on Minerals, 46. Moscow. 13-19).
The alkaline massif has boron-rich granitoids intruding into schists, crossed by metasomatite and pegmatite veins. The pegmatites resulted from the differentiation of a silicic melt to the point where saturation in boron is attained under vapour unsaturation with reedmergnerite + orthoclase / microcline / quartz assemblage (T = 450 to 500°C, P less than 2kbar).
Note: This locality is in a very remote area with hostile actors in the area. Recent access has been by helicopter (Mindat).
Orlovite from the Dara-i-Pioz Massif

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