Andalusite Visible Spectra (380 - 1100 nm)

Andalusite, Al2(SiO4)O, obtains a greenish yellow color from Fe3+. If Mn3+ is in the structure, a dark green color results. The intense brownish-red color commonly observed for light polarized in the c direction is the result of strong absorption from the Fe2+ - Ti4+ intervalence charge transfer centered near 480 nm. Many samples contain an admixture of colors from Fe, Ti and Mn. Varieties containing vanadium [V3+] and chromium are known which have reddish-brown colors. 

    Manganese-containing andalusite (variety viridine)

Link to a collection of references to mostly color and visible spectroscopy of andalusite.

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revised 5-Jul-2022