Sauconite

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Sauconite
Sauconita.jpg
Sauconite (reddish brown)
General
Category Phyllosilicate mineral
Formula
(repeating unit)
Na0.3Zn3(SiAl)4O10(OH)2·4H2O
Strunz classification 9.EC.45
Crystal system Monoclinic
Crystal class Prismatic (2/m)
(same H-M symbol)
Space group C2/m
Identification
Color Reddish brown, brown, brownish yellow, mottled
Crystal habit Clayey; as small micaceous plates in laminated to compact masses
Cleavage Perfect on {001}
Mohs scale hardness 1 - 2
Luster dull
Diaphaneity Translucent
Specific gravity 2.45
Optical properties Biaxial (-)
Refractive index nα = 1.550 - 1.580 nβ = 1.590 - 1.620 nγ = 1.590 - 1.620
Birefringence δ = 0.040
Dispersion r > v strong
References [1][2][3]

Sauconite is a complex phyllosilicate mineral of the smectite clay group, formula Na0.3Zn3(SiAl)4O10(OH)2·4H2O. It forms soft earthy bluish white to red-brown monoclinic crystals typically massive to micaceous in habit. It has a Mohs hardness of 1 to 2 and a specific gravity of 2.45. Optically it is biaxial positive with refractive index values of nα = 1.550 - 1.580, nβ = 1.590 - 1.620 and nγ = 1.590 - 1.620.[1][3] It is found in vugs and seams in the oxidized zones of zinc and copper deposits. It occurs in association with hemimorphite, smithsonite, chrysocolla, coronadite and various iron oxides.

It was named for the Saucon Valley in Pennsylvania, where it was originally discovered in 1875.[2]

References[edit]