Colour

Green, yellowish green, bluish green.

Cause of colour

Chromium

Optical Character

Uniaxial negative

Pleochroism

Distinct; Two shades of green, o ray – green, e ray – bluish green

Colour change

No

Spectrum; no polar Calibration in nm.

Violet absorbed. Broad band over orange & yellow/green, moderate line at 637.weak lines at 646 & 662. Doublet at 680/683.

Ordinary ray

As above plus a weak narrow line at 477 in Cr. rich stones. The broad band becomes narrower to reveal a stronger 637 line and the lines at 646 & 662 are missing. The doublet is weaker.

Extraordinary ray

Violet absorbed. The broad band widens to obscure the lines at 637 & 642. The 662 strengthens. The 683 in the doublet is the stronger.

Alpha ray

Not applicable

Beta ray

Not applicable

Gamma ray

Not applicable

Emission lines

No

Database reference

GN1 and GN3

Notes

The broad band is faint and lines weaker in pale coloured stones