Visible spectrum of hornblende (3).

View of another crystal orientation. Polarizer direction is close to X axis for the yellow crystals and close to Z axis for the blue ones.

Spectra of the elongated blue-yellow hornblende crystals. The dark blue orientation is close to Z axis. The charge transfer band is the strongest. In the perpendicular orientation, the light vibration direction is close to X axis. In this case, the charge transfer band Fe++ ---> Fe+++ almost disappears. The yellow color is due to the end of a strong UV band.

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