Polarized electronic single crystal spectra of natural Fe2+ ion-bearing oxygen-based minerals, in which ferrous ions enter octahedral sites of different symmetry and distortion (olivine, cordierite, ortho- and clinopyroxene, ...

Single crystals of several varieties of dumortierite, an orthorhombic, pseudohexagonal borosilicate mineral with spectacular colour and pleochroism, were studied by electronic absorption spectroscopy and electron-microprobe ...

Pyrope-knorringite garnets, Mg3(Al1-X Cr3+X)2Si3O12 with X=0.25, 0.50, and 1.00, were synthesized between 9 and 16 GPa and 1300 and 1600 °C, using multianvil high-pressure techniques. The garnets with X=0.25 and 0.50 are ...

A distinctive feature of Ukrainian deep-violet diamond microcrystals is a broad absorption band centered at about 560 nm (17850cm(-1) or 2.21 eV). In the Ukrainian samples, the intensity of this band is almost two orders ...

Polarized optical absorption spectra of a rare Fe2+, Fe3+-bearing silicate mineral, tuhualite, (Na,K)2Fe22+Fe23+Si12O30, were measured at room temperature in the range 350–4000 nm (ca. 28500–2500 cm–1). The spectra display ...

Unpolarized, (X,Y)-mixed electronic absorption spectra were measured on (001) plates of two natural orthopyroxenes with 24 and 45 mole % ferrosilite and with a Ca content 0.07 atoms pfu, at pressures up to 10.3 and 8.83 ...