566 



DETERMINATION OF PRECIOUS STONES 



A. TRANSPARENT STONES. 



These are classified into fourteen groups according to colour : 



1. Colourless • 



2. Greenish-blue (sea-green) 



3. Pale blue 



4. Blue 



5. Violet 



6. Lilac and rose 



7. Bed 



8. Keddish-brown 



9. Smoke-grey and clove-brown 



10. Eeddish-yellow 



11. Yellowish-brown 



12. Yellow 



13. Yellowish-green 



14. Green 



In the tables which follow, each markedly transparent precious stone will be found in 

 one of these fourteen groups, and in cases where the same stone shows two or more colours, 

 or a shade more or less in harmony with the colours characteristic of several groups, it will 

 be included in each, so that there will be no difficulty in finding it. The stones 

 included in each colour-group are further classified according to specific gravity, as 

 determined by the four standard heavy liquids. They are placed in the tables in order of 

 decreasing specific gravity, and in three other colunms are tabulated the values of the specific 

 gravity and hardness, and the character of the refraction of each ; while in a fourth column 

 the presence or absence of dichroism, its strength, and, in some cases, the colours of the 

 dichroscope images are indicated. 



It should be possible from these tables to establish the identity of almost any precious 

 stone one may happen to meet with. The remarks appended to each table are intended as 

 a help, mainly in cases where the specific gravity places several stones in one or other of the 

 five sub-divisions. 



The names of the more important jirecious stones, and those most commonly met with, 

 are printed in the tables in heavier type, and special attention is paid to such in the 

 remarks. 



1. COLOURLESS STONES. 



The stones included in Division I. sink in liquid No. 1, and this high specific gravity is 

 a feature which marks them off from all the others. They are distinguished inter se by 

 differences in their optical characters, zircon and corundum (" white sapphire ") being 



