Sugilite

Class: Silicates
Group: Osumilite

In an aegirine-bearing syenite stock in biotite granite (Iwagi Islet, Japan); in manganese deposits (near Kuruman, South Africa) (Anthony et al., 2001—2005).

Sugilite — specimen 0040, photo © NMNHS

Original description: Murakami, N., Kato, T., Miúra, Y., Hirowatari, F., 1976. Sugilite, a new silicate mineral from Iwagi Islet, Southwest Japan — Mineralogical Journal 8: 110—121 [view in ‘Library’].

Type locality: Iwagi Island, Ehime Prefecture, Japan.

Type material: National Museum of Natural History, Smithsonian Institution, Washington, DC, USA, 133982; National Museum of Nature and Science, Tokyo, Japan; Natural History Museum, London, England, 1975, 342; Yamaguchi University, Yamaguchi, Japan (Anthony et al., 2001—2005).

Etymology: in honour of Kenichi Sugi, Japanese petrologist (Anthony et al., 2001—2005).

Distribution: Japan: Ehime Prefecture: Iwagi Islet; South Africa: Wessels mine near Kuruman (Anthony et al., 2001—2005).

Chemistry

KNa2Li3Fe2[Si12O30]

Essential elements: lithium (Li), oxygen (O), sodium (Na), silicon (Si), potassium (K), iron (Fe).

Crystal data

Crystallography: hexagonal — dihexagonal dipyramidal. Crystal habit: crystals prismatic, to 2 cm; commonly massive (Anthony et al., 2001—2005).

Physical properties

Cleavage: on {0001}, poor (Anthony et al., 2001—2005). Fracture: no data. Tenacity: no data. Hardness: 6—6.5 (Arem, 1987: 182). Density: 2.74 g/cm3 (Arem, 1987: 182). Luminescence: none (Arem, 1987: 182).

Optical properties

Colour: light brownish yellow to bright magenta; nearly colourless in thin section (Anthony et al., 2001—2005). Diaphaneity: transparent to translucent (Anthony et al., 2001—2005). Lustre: vitreous (Arem, 1987: 182). Refractive index: 1.606—1.61 — anisotropic [uniaxial (-)] (Arem, 1987: 182). Birefringence: 0.003. Dispersion: none. Pleochroism: none.

Material from ‘Repository’

1 specimen: 0040 — 0.17 ct, South Africa, Northern Cape, Kuruman, Wessels mine.

→ Gallery view