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 GEMSTONE SPECTRA

(EXCEL FILES)

  COLOURLESS STONES

 CS1

 RED STONES  

   RD1 Dark red

   RD2 Pinkish red

  RD3 Orangy red

RD4 Slightly purplish red

  RD5  Purplish red

PINK STONES 

  PK1 Lilac pink

   PK2 Pink and orangy pink

PK3  Brownish and purplish pink

ORANGE STONES

OR1

YELLOW STONES

YL1

GREEN STONES

GN1 Green

GN2 Yellowish and greyish green

GN3 Bluish green

GN4 Dark and brownish green

BROWN STONES

BN1 Light brown

BN2 Dark brown

BLUE STONES

BL1 Blue

BL2 Greenish blue

BL3 Lavender and indigo blue

VIOLET AND PURPLE STONES

VT - PL Violet and Purple

 Periodically other gemstones will be added to these files

 

Diffraction spectra of yellow, green and brown chrysoberyl

See my  DECLARATION OF COPYRIGHT

Colour Properties of  yellow, brown and green Chrysoberyl

Colour

Pale greenish yellow to shades of green, greenish brown and brown.

Cause of colour

Iron; Small traces of chromium may contribute to some green stones

Optical Character

Biaxial positive         

Pleochroism

Often  just two shades of body colour detected; α -  darker;  γ - paler

Colour change

No, but some green stones may appear a more brownish green in tungsten light.

Spectrum; no polar, calibration in nm.

Main band due to iron centred at 444nm.easily resolved in yellows but more difficult in browns and may cut off in dark greens at 450.Weaker lines may be seen in darker browns at 485 and 505.

Ordinary ray

Not applicable

Extraordinary ray

Not applicable

Alpha ray

444 band and others are stronger and broader in this direction

Beta ray

Untested  - awaiting a suitable single crystal for observation.

Gamma ray

444 band narrower. Weak Cr. line at 680 in some green stones

Emission lines

No

Database reference

YL1 and GN2

Notes

Some green chrysoberyl may also show a very weak line at 680 due to Cr. and absorb strongly in the deep blue to mask the 444 iron band. A slight colour shift occurs and such stones may appear red under crossed colour filters.  - In my opinion these are not Alexandrite. See GN2

Copyright John S. Harris 2000-2016

 

SPECTRA OF

 PRINCIPAL 

COMMERCIAL GEMS

ALEXANDRITE

ALMANDINE GARNET

DIAMOND

EMERALD

GREEN JADEITE

PERIDOT

RUBY

BLUE SAPPHIRE

RED SPINEL

GREEN & BLUE SPINEL

  SYN. BLUE SPINEL &  Co. GLASS

SYN. COLOUR CHANGE CORUNDUM

ZIRCON (High type)

ZIRCON (Low type)

Other pages are under construction

COLOUR FILTERS

 (EXCEL FILES)    

CF1 Basic Colour Filters

CF2 Special Colour Filters

EDUCATIONAL C. D.

  A GUIDE TO THE   SPECTROSCOPE