Nuolayniemi deposit, Pitkyaranta mining district, Pitkyarantsky District, Republic of Karelia, Russiai

Regional Level Types
Nuolayniemi deposit	Vein (Inactive)
Pitkyaranta mining district	Mining District (Abandoned)
Pitkyarantsky District	District
Republic of Karelia	Republic
Russia	Country

The pegmatites of the Nuolainiemi peninsula belong to the pegmatites of the first post-Ladoga group. They form large, usually rectilinear veins, gradually wedging out in length and depth. Very large crystals and feldspar segregations are observed in them - solid or intergrown with quartz, with the formation in the latter case of the so-called graphic pegmatite. The biotite in these pegmatites forms large saber-shaped plates, and sometimes large irregular aggregations or nests.

A characteristic feature of the described pegmatites is often a zonal structure. They are also interesting in that they include such relatively rare minerals as allanite ("orthite"), monazite, xenotime, zircon ("cyrtolite" variety, "wiikite" (ill-defined) and others. However, it is difficult to find these minerals, since they are not distributed throughout the body of the pegmatite vein, but only locally and, moreover, form small crystals.

Allanite is most frequently present in the marginal parts of pegmatite veins, in plagioclase areas, where it forms elongated, almost acicular crystals of rhombic cross-section, colored brown, rarely black, and surrounded by a rusty border.

Other rare minerals are best found where feldspars and quartz are cut through by sheets of biotite. In this case, monazite forms brown envelope-like prismatic crystals, while xenotime forms dipyramidal elongated crystals similar to "cyrtolite" crystals, but the latter are much more elongated. "Wiikite" forms brown, brown, black and yellow discharges, rounded in shape with a resinous sheen and conchoidal fracture.

"Yttropyrochlore-(Y)" - original locality (type locality).

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References