Lizardite

Lizardite is a mineral from the serpentine subgroup with formula Mg3(Si2O5)(OH)4, and the most common type of mineral in the subgroup. It is also a member of the kaolinite-serpentine group.

Lizardite
General
CategoryMineral
Formula
(repeating unit)
Mg3(Si2O5)(OH)4
IMA symbolLz
Strunz classification9.ED.15
Dana classification71.01.2b.02
Crystal systemTrigonal
Identification
ColorGreen, brown, light yellow to white
Mohs scale hardness2.5
LusterResinous, waxy, greasy
StreakWhite
Specific gravity2.55

Lizardite may form a solid-solution series with the nickel-bearing népouite (pure end-member: Ni3(Si2O5)(OH)4). Intermediate compositions (Mg,Ni)3(Si2O5)(OH)4 are possible, with varying proportions of magnesium and nickel. However, the lizardite end-member is much more common than pure népouite, a relatively rare mineral most often formed by the alteration of ultramafic rocks.

Extremely fine-grained, scaly lizardite (also called orthoantigorite) comprises much of the serpentine present in serpentine marbles. It is triclinic, has one direction of perfect cleavage, and may be white, yellow or green. Lizardite is translucent and soft, and may be pseudomorphous after enstatite, olivine or pyroxene, in which case the name bastite is sometimes applied. Bastite may have a silky lustre.

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