Weloganite

Weloganite

Weloganite
General
Category Carbonate mineral
Formula
(repeating unit)		 Na2(Sr,Ca)3Zr(CO3)6·3H2O
Strunz classification 5.CC.05
Dana classification 15.3.4.4
Crystal system Triclinic
Crystal class Pedial (1)
(same H-M symbol)
Space group P1
Unit cell a = 8.966 Å, b = 8.98 Å
c = 6.73 Å; α = 102.72°
β = 116.65°, γ = 60.06°; Z = 1
Identification
Formula mass 814.16 g/mol
Color Yellow, pale yellow, amber, tan, white
Crystal habit Roughly hexagonal, tapering crystals, pseudorhombohedral
Twinning About [103] repeated at 120 degrees
Cleavage Perfect on pseudo {0001}
Fracture Conchoidal
Mohs scale hardness 3½
Luster Vitreous
Streak White
Diaphaneity translucent
Specific gravity 3.20 - 3.22
Optical properties Biaxial (-)
Refractive index nα = 1.558 nβ = 1.646 nγ = 1.640
Birefringence δ = 0.082
2V angle Measured: 15°
Dispersion Weak
Other characteristics Pyroelectric. triboluminescent.
References [1][2][3][4][5]

Weloganite is a rare carbonate mineral with formula: Na2(Sr,Ca)3Zr(CO3)6·3H2O. It was discovered by Canadian government mineralogist Ann P. Sabina in 1967 and named for Canadian geologist Sir William Edmond Logan (1798–1875). It was first discovered in Francon Quarry, Montreal, Canada and has only been reported from a few localities worldwide.

Properties

It is usually white, lemon yellow, or amber in color, and can be translucent. It crystallizes in the triclinic system and shows pseudo-hexagonal crystal forms due to twinning. The width of the crystals typically undulates down the length, forming crystals that widen in the middle or flare out at the end. Crystals are affected by light and can develop a white alteration coating over time. Weloganite is triboluminescent, producing blue light.

Occurrence

It occurs in an igneous carbonatite sill in Montreal, Canada in the Francon Quarry where it was first discovered. It also occurs in the Mont Saint-Hilaire district. Associated minerals include strontianite, dawsonite and calcite. It has also been reported from the Pilansberg Complex of the western Bushveld Igneous Complex in South Africa.[4]

See also

References

  1. ↑ Sabina, A., 'Weloganite, a new strontium zirconium carbonate from Montreal Island, Canada', The Canadian Mineralogist, 9, pp.468-477, 1968.
  2. ↑ Grice, J. D. and Perrault G., 'The crystal structure of triclinic weloganite', The Canadian Mineralogist, 13, pp.209-216, 1975.
  3. ↑ Handbook of Mineralogy
  4. 1 2 Mindat
  5. ↑ Webmineral


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