Lizardite

Class: Silicates
Group: Kaolinite-serpentine

Typically a product of retrograde metamorphism, replacing olivine, orthopyroxene, or other minerals in ultramafic rocks (Anthony et al., 2001—2005).

Lizardite — specimen 0656, photo © NMNHS

Original description: Whittaker, E. J. W., Zussman, J., 1956. The characterization of serpentine minerals by X-ray diffraction — Mineralogical Magazine 31: 107—126 [view in ‘Library’].

Type locality: Eastern Cliff, Kennack Cove, Kennack, Lizard Peninsula, Cornwall, England, UK; North shore of Lake Superior, Minnesota, USA.

Type material: Natural History Museum, London, England, 1955, 243; National Museum of Natural History, Smithsonian Institution, Washington, DC, USA, 114569 (Anthony et al., 2001—2005).

Etymology: for the type locality, the Lizard Peninsula, Cornwall, England.

Distribution: probably the most common serpentine mineral: Australia; Canada; England; Italy; Japan; USA (Anthony et al., 2001—2005).

Chemistry

Mg3Si2O5(OH)

Essential elements: hydrogen (H), oxygen (O), magnesium (Mg), silicon (Si).

Crystal data

Crystallography: triclinic — pinacoidal. Crystal habit: crystals rare, to 2 mm, as trigonal plates to truncated trigonal pyramids; commonly as extremely fine-grained scales and massive aggregates (Anthony et al., 2001—2005).

Physical properties

Cleavage: perfect on {0001} (Anthony et al., 2001—2005). Fracture: crystals are easily bent (Anthony et al., 2001—2005). Tenacity: no data. Hardness: 2.5 (Anthony et al., 2001—2005). Density: 2.55 g/cm3 (Anthony et al., 2001—2005). Luminescence: none.

Optical properties

Colour: green, light yellow to white; colourless to pale green in thin section (Anthony et al., 2001—2005). Diaphaneity: translucent (Anthony et al., 2001—2005). Lustre: waxy (Anthony et al., 2001—2005). Refractive index: 1.538—1.560 — anisotropic [biaxial (-)] (Anthony et al., 2001—2005). Birefringence: 0.012. Dispersion: none. Pleochroism: none.

Material from ‘Repository’

1 specimen: 0656 — 0.55 ct, no locality data.

→ Gallery view