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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

 

 

INTRODUCTION 
 

This database is mainly for use by students studying gemmology in the courses offered by the Gemmological Association of Great Britain and the National Association of Jewellers

In these courses a sound knowledge of gemstone spectroscopy is essential, together with the ability to recognise the absorption and fluorescence spectra of many of the gem materials included in their syllabus. It is hoped that Gemmologists and those working with and trading in gemstones from other countries, may also find it useful as a general reference guide when comparing spectra of gemstones, collectors minerals and other material for identification. The database will eventually include common, unusual and rare gemstones, synthetic and artificial gemstones. Other sections will include rare collectors minerals and artificial materials used in modern technology. There will also be sections dealing with filters, liquids and the emission spectra of light sources used in the examination and testing of gem material.

As the work is extensive it will be released in sections to which extra items can be inserted periodically as they are recorded and photographed.

 

THE GEMSTONE SECTIONS

  GEMSTONE SPECTRA COMPARISON  follow the links in column on the left to view the EXCEL FILES

These have to be easily accessed and used by students. After much deliberation and discussion with colleagues I have simply arranged it by colour, which is the primary consideration in any initial investigation.There is unavoidable repetition of similar spectra which occur in the different hues, or even in the different colours of certain gemstones. However slight variations may occur which can be important features in identification.

              PRINCIPAL COMMERCIAL GEMSTONES  follow the links in the column on the right to view their individual pages
                                                                                                                                                                                                                  Although most specimens of a particular species will show a similar pattern in their spectra, the student must realise a gemstone spectrum can be unique in that not all of the absorption or fluorescent lines may be present to the same degree in all specimens This is due to several factors such as colour saturation, size of stone, transparency and colour temperature and intensity of the light source. The resulting spectrum, or spectra in the case of some pleochroic gemstones, should therefore be regarded as a "Colour Signature" for that particular specimen. This is illustrated in the various specimens shown in  some of the individual pages for the Principal Commercial Gemstones

 

THE IMAGES

Unlike many drawings, diagrams and coloured illustrations, these photographs reveal what a student may expect to see through a hand held direct vision diffraction spectroscope. In some cases the absorption lines may be strong and bold, in others they may be weak and vague just as we often find them. There are some spectra in which the camera has failed to resolve some of the finer lines and others where it has revealed certain lines which are seldom detected be eye, such as those in the violet region.  The limitations of digital colour photography can affect different areas of the spectrum such as a lower intensity in the yellow and an increase in the green. However, the overall impression is generally as the student should see the images. In some cases it has been necessary to over expose in the deep blue – violet in order to resolve some lines in that area, hence the imbalance of colour in some photographs.

ACKNOWLEDGEMENTS

The majority of the gemstone spectra are from specimens in the authors private teaching collection. However some are from specimens kindly on loan from Alan Hodgkinson (specimens prefixed AH) and Dr. Jamie Nelson (specimens prefixed JBN.) My thanks go to them and all my colleagues and fellow gemmologists for their help and encouragement  in compiling this database.

 

 

Copyright John S. Harris 2000-2016

Copyright John S. Harris 2000-2015

  

SPECTRA OF

 PRINCIPAL 

COMMERCIAL GEMS

ALEXANDRITE

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