Colour

Green,  dark green to brownish green and greenish blue

Cause of colour

Chromium

Optical Character

Biaxial Positive        

Pleochroism

Red (or purplish),orange and green (or greenish blue) in various hues.

Colour change

Green in daylight, red in tungsten, distinct to weak in variable hues.

Spectrum; no polar Calibration in nm.

Absorption to up to about 460. Broad absorption centred at 590. Lines in orange at 645;649;655;665; Doublet in red at 678/680.

Ordinary ray

Not applicable

Extraordinary ray

Not applicable

Alpha ray           Red

Absorbs to about 460. Line at 472;  Broad absorption shifts towards short wave centred at 570;  649 & 665 missing. Others weak.

Beta ray       Orange

Absorbs up to 480. Mainly a weak band in the yellow/green at 570

Gamma ray    Green

Absorbs up to 470. Broader absorption shifts towards long wave  centred at 595 obscuring some lines in orange.  645 & 680 stronger.  

Emission lines

Seldom seen but visible in some synthetics at 678/680

Database reference

GNF0663 (Russian)and GNF0859 (Sri Lankan)in GN4

Notes

A variety of chrysoberyl. Line at 472 seen in chromium rich stones