Grandidierite Visible Spectra (350 - 2500 nm)
Grandidierite, (Mg,Fe2+)(Al,Fe3+)3(SiO4)(BO3)O2, is a mixed oxidation state iron mineral.
- GRR
441 spectrum; from Metroka, Madagascar, CIT#8376, 0.50 mm
thick sample. The color of this material comes from the Fe2+
ion and its interaction with Fe3+ and varies
considerably with the direction in which it is observed. It is blue
when polarized parallel to the a-axis to pale to colorless when
parallel to the other axes. Data Files: E||a=alpha 74K; E||c=beta 68K; E||b=gamma 74K;
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