Weloganite

Weloganite is a rare carbonate mineral with the 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,^[7] Montreal, Quebec, Canada and has only been reported from a few localities worldwide.

Weloganite
General
Category	Carbonate mineral
Formula	Na2(Sr,Ca)3Zr(CO3)6·3H2O
IMA symbol	Wlg[1]
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	3+1⁄2
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	[2][3][4][5][6]

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

The mineral occurs in an igneous carbonatite sill in Montreal, Quebec, 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.^[5]

See also

• List of minerals
• List of minerals named after people