Dundasite

Dundasite
Dundasite (the white mineral) and crocoite from Dundas, Tasmania. Field of view is 5mm.
General
Category	Carbonate mineral
Formula (repeating unit)	PbAl2[(OH)2|CO3]2 • H2O
Strunz classification	5.DB.10
Crystal system	Orthorhombic
Crystal class	Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m)
Space group	Pbmm
Unit cell	a = 9.08, b = 16.37 c = 5.62 [Å]; Z = 4
Identification
Color	White to very pale blue; colorless in transmitted light
Crystal habit	Acicular crystals typically in spherical aggregates and matted crusts
Cleavage	Perfect On {010}
Mohs scale hardness	2
Luster	Vitreous to silky
Streak	White
Diaphaneity	Transparent
Specific gravity	3.10 – 3.55
Optical properties	Biaxial (-)
Refractive index	nα = 1.603 nβ = 1.716 nγ = 1.750
Birefringence	δ = 0.147
2V angle	Measured: 30° to 40°, calculated: 54°
References

Dundasite is a rare lead aluminium carbonate mineral. The mineral is named after the type locality, Dundas, Tasmania, Australia. The mineral was first discovered in the Adelaide Proprietary Mine. Dundasite was first described by William Frederick Petterd in 1893.

Dundasite is an uncommon secondary mineral occurring in the oxidized zone of lead ore deposits. It commonly overgrows crocoite. It may also be overgrown by yellow cerussite. It may be associated with cerussite, plattnerite, azurite, malachite, pyromorphite, mimetite, beudantite, duftite, crocoite, gibbsite, allophane and limonite.

Besides its type location on Tasmania, the mineral has also been found in New Zealand, Mainland Australia, China, Belgium, Germany, France, Greece, United Kingdom, Ireland, Italy, Austria, Czech Republic, Namibia, and the US.