A platy trioctahedral member of the serpentine group. The ideal, end-member formula is: Mg3Si2O5(OH)4. Typical site substitutions include Al and Fe3+ for Si and Mg. The most common form of lizardite is the 1T polytype (space group P31m), followed by the 2H1 polytype (space group P63cm). Lizardite is the most abundant serpentine and forms from the weathering (hydration) of ultramafic rocks, primarily composed of olivine and pyroxene.