Class: Silicates
Group: Scapolite
Original description: ‘Màrialith’ vom Rath, G., 1866. 5. Mineralogisch-geognostische Fragmente aus Italien — Zeitschrift der Deutschen Geologischen Gesellschaft 18: 636—637 [
view in ‘Library’].
Type locality: Pianura, Phlegrean Fields, Naples Province, Campania, Italy.
Type material: unknown.
Etymology: named by Gerhard vom Rath in honour of his wife, Maria Rosa vom Rath.
Distribution: Brazil: Minas Gerais; Canada; Italy: Pianura, west of Naples, Campania; Madagascar; Mexico; Myanmar: Mogok district; Russia: near Lake Baikal, Siberia; Tanzania (
Anthony et al., 2001—2005).
Chemistry
3NaAlSi3O8·NaCl
Essential elements: oxygen (O), sodium (Na), aluminium (Al), silicon (Si), chlorine (Cl).
Crystal data
Crystallography: tetragonal — dipyramidal.
Crystal habit: crystals prismatic, typically with flat pyramidal terminations, striated, to 1.5 m; granular, massive (
Anthony et al., 2001—2005).
Optical properties
Colour: colourless, white, grey, pink, violet, blue, yellow, brown, orange-brown; colourless in thin section (
Anthony et al., 2001—2005).
Diaphaneity: transparent to opaque (
Anthony et al., 2001—2005).
Lustre: vitreous, pearly, resinous (
Anthony et al., 2001—2005).
Refractive index: 1.539—1.55 — anisotropic [uniaxial (-)] (
Anthony et al., 2001—2005).
Birefringence: 0.004—0.008.
Dispersion: none.
Pleochroism: none.
Material from ‘Repository’
8 specimens: 0097 — 2.78 ct, Namibia;
0195 — 1.11 ct, Tanzania;
0196 — 1.47 ct, Tanzania;
0255 — 0.39 ct, Tanzania;
0081 — 0.20 ct, Tanzania;
0082 — 0.30 ct, Tanzania;
0334 — 0.22 ct, Tanzania;
0335 — 0.19 ct, Tanzania.
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