Oxides and hydroxides: Pyroclor

Diagnostic card.

(Na, Ca, U) ₂ (Nb, Ta, Ti) ₂ O ₆ (OH, F)
Cubic amount of cubic zirconia
Hardness 5-5,5
Specific weight 4,3-4,5
Cleavage is difficult to determine
Cracked shell
Color yellow, red, brown
Shine greasy

The chemical formulas of pyrochlore and microlite (in the photo above) are identical, but the microlite differs by the predominance of tantalum over niobium. Represented by distinctly formed crystals, almost exclusively octahedra, which sometimes due to the cutting of the vertices by small faces are transformed into rhombododecahedrons. The color of pyrochlore is brown, and the microlite is pale yellow to reddish-brown, sometimes emerald green. Color yellow-brown, reddish-brown, brown to brownish-black, also light brown, amber-yellow, pale yellow to colorless, occasionally green, yellowish- and olive-gray (pandaite). In crystals, the color is often distributed unevenly: the core differs in color. Can not be stored at home.

Cleavage is usually not observed, sometimes imperfect cleavage or separation according to (111). Aggregates - Crystals are usually small, sometimes reaching 10 cm or more, clusters of crystals, fine crystalline aggregates. Crystals are usually octahedral. Often they are imperfect, sometimes flattened along the edges of the octahedron. Crystals are sometimes zonal.

Diagnostic signs.
In crystals, these minerals can be determined by a clearly expressed octahedral shape. Radioactive to a varying degree in accordance with the different contents of uranium and thorium, sometimes only certain zones of crystals are radioactive. After calcination, it luminesces in the rays of a mercury quartz lamp.

Origin.
These are typical minerals of pegmatites - derivatives of alkaline rocks. Dark-colored differences appear only in thin fragments; Hydrated pyrochlore is opaque.

Deposits and applications.
Pyroclor is sometimes found in significant quantities, both at Mbeya in Tanzania and in the Fen area in Norway. A rarer species (koppit) is found in the Kaiser-piece in Germany, associating it with magnesioferrit, forsterite and apatite. Excellent pyrochlore crystals are present in calciphyres from the Oka deposit (Canada). The classical locations of the microlite are in the state of Maine, Amylia-Court House in Virginia, Heddam in Connecticut (USA), Betanama in Madagascar and Va-Rutresk in Sweden. Both minerals are of great importance due to the high content of rare elements.

Pyroclor. Tatarskiy mn, Tatarka river, Yenisei ridge, Av. Siberia (S), Russia. Photo: © А.А. Evseev.

Pyroclor. The dangerous "Babylonian stone" is radioactive and causes hallucinations. Photo: © А.А. Evseev.

Uranpyrochlor. Beryl Hill, Zap. Australia. Photo: © А.А. Evseev.

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