Blue color in sodic plagioclase is produced by electronic transitions of Pb in a manner similar to the mechanism causing color in amazonite (potassium feldspar colored blue-green by Pb electronic transitions). The two blue feldspar varieties have the following characteristics in common: (1) elevated Pb concentrations( usually greater than 0.01 wt.%), (2) structurally incorporated H+, (3) similar response of the color to heating and irradiation, and (4) similar band shape, position, and polarization in the optical spectrum.

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