Colour

Blue; Greenish blue; Bluish green; Dark green; Pale to deep yellow.

Cause of colour

Titanium-Iron(transfer charge); Iron (Fe.2+); Iron (Fe3+):

Optical Character

Uniaxial Negative    

Pleochroism

Distinct as two shades of blue, green or yellow. Yellows very weak.

Colour change

No

Spectrum; no polar Calibration in nm.

Three lines at 450; 460; 471; Fine blues may only show the 450 line Bluish greens can display all three and in dark greens and yellows two or three may merge as a single broad band.

Ordinary ray

Any bands present are seen at their strongest in this ray.

Extraordinary ray

Similar but weaker

Alpha ray

Not applicable

Beta ray

Not applicable

Gamma ray

Not applicable

Emission lines

No

Database reference

None yet

Notes

Sri-Lankan pale blues and yellows may only show a very weak 450: