Sillimanite Visible Spectra (generally 350 - 1200 nm)

Images of representative sillimanites

Visible Spectra: polarizations: (a = alpha direction; b = beta direction; g = gamma direction) Fe³⁺ is usually responsible for the yellow color in sillimanite. Other colors can occur when intervalence charge transfer is involved.

• GRR 273 spectrum; sillimanite, GRR 273, Reinbolt Hills, Antactrica, 2.7 mm thick with a typical yellow color from Fe³⁺. Reference: Rossman et al. (1982) Amer. Mineral 67, 749-761. Data Files: a 9K; g 5K
• GRR 444 spectrum; Sillimanite, GRR 444, Ceylon, 10.0 mm thick. Blue color from intervalance charge transfer. Data Files: a 3K ; c 4K
• GRR 382 spectrum; Sillimanite, GRR 382, Sardinia, plotted as 0.50 mm thick. Purple-brown color from Fe³⁺ and intervalance charge transfer presumed to be from Fe²⁺ and Ti⁴⁺. Data Files: a 3K ; b 1K ; g 6K

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