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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 alexandrite

See my  DECLARATION OF COPYRIGHT

Colour Properties of Alexandrite

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

For the relationship between Colour Change, Pleochroism and Absorption Spectra in Alexandrite see the entry for July 2012 in

THROUGH MY SPECTROSCOPE

Copyright John S. Harris 2000- 2016

 

SPECTRA OF

 PRINCIPAL 

COMMERCIAL GEMS

ALMANDINE GARNET

CHRYSOBERYL

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