Weloganite

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Weloganite
Weloganite2(11x5.5).jpg
Weloganite
General
Category Carbonate mineral
Formula
(repeating unit)
Na2(Sr,Ca)3Zr(CO3)6·3H2O
Strunz classification 05.CC.05
Dana classification 15.3.4.4
Crystal symmetry Triclinic 1 pinacoidal
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
Color Yellow, pale yellow, amber, tan, white
Crystal habit Roughly hexagonal, tapering crystals
Crystal system Triclinic, pseudorhombohedral
Twinning About [103] repeated at 120 degrees
Cleavage Perfect on pseudo {0001}
Fracture Conchoidal
Mohs scale hardness
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 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[edit]

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[edit]

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[edit]

References[edit]

  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. ^ a b Mindat
  5. ^ Webmineral

External links[edit]