630 GEMS 



White sapphire .... S.G. 4-0 H. 9 D.B. 



White spinel 3 -5 ,,8 S.B. 



Whito zircon 



White beryl 



Phonakite . . . 



Tourmaline 



Euclase , . 



lied Gems. 



47 7-5 D.B. 



2-6 ., 7'5 D.B. 



3-0 7-5 D.B. 



3-0 7 D.B. 



3-0 7'5 D,B. 



The following are the chief stones of this colour, to which may be added the red 

 diamond, which occurs, however, but rarely : 



Buby S.G. 4 H. 9 D.B. 



Spinel 3-5 ,,8 8.K. 



Garnet . . . . . . 3-8 , r 7'5 S.B. 



Topaz . . . . b . 3-5 ,,8 D.B. 



Bubellite ,,3 7'5 D.K. 



Most of these stones present colours which are sufficiently distinct to be discriminated 

 by the experienced eye. The ruby (true or oriental ruby) varies in tint from rose-red 

 to carmine, the most esteemed stones presenting a deep rich red colour, called by 

 jewellers pigeons' blood. The spinel (spinel ruby and balas ruby) is less brilliant in 

 tint than the true ruby, and presents a variety of shades, some of which resemble the 

 colours of certain garnets ; the variety known as balas ruby is distinguished by a rose- 

 pink colour, tending to blue. Garnets offer considerable variation in colour; the 

 Bohemian garnet^pyrope) being of a dark fiery red, and the Oriental or Syrian garnet 

 (almandine) varying in colour from deep crimson to violet. The topaz is never de- 

 cidedly red, but sometimes presents a delicate pink tint, which is produced by the 

 action of heat on stones which are normally of a yellow colour. Bubellite (red 

 tourmaline) is characterized by becoming highly electric when heated or when exposed 

 to friction. 



By aid of the dichroiscope the red colour of the oriental ruby may be resolved either 

 into a pale and a dark rose-red, or into a bluish and a yellowish red. The spinel and 

 garnet, being singly-refracting species, do not admit of dichroiscopic examination. 



Brown Gems. 



Essonite S.G. 3'6 H. 7'5 S.B. 



Hyacinth 47 7'5 D.B. 



Tourmaline 3'0 7'5 D.B. 



Brown quartz 2-6 ,,7 D.B. 



Essonite (cinnamon stone or garnet) and hyacinth (zircon) present very similar 

 colours a fine reddish brown but are readily distinguished by specific gravity. In 

 the dichroiscope the colour of the zircon is resolved into a mixture of brown with 

 greenish yellow and brown with red. 



The brown tourmaline yields images of similar colours, and brown quartz gives a 

 yellowish brown and a violet-brown image. 



A few other stones of a brown colour are occasionally met with, namely : brown 

 diamond, chrysoberyl, axinite, idocrase, andalusito, and epidote. 



Yellow Gems. 



Topaz S.G. 3-5 H. 8 D.B. 



Chrysoberyl ,>7 8'5 D.B. 



Yellow beryl i . . 27 ,,8 D.B. 



Yellow quartz 2'6 ,,7 D.B. 



Zircon ,,47 7'5 D.B. 



Oriental topaz ,,4 ,,9 D.B. 



The colour of the topaz is a straw-yellow or wine-yolbw ; that of the chrysoboryl a 

 greenish yellow ; and of the zircon a brownish yellow. The true topaz, false topaz 

 (yellow quartz), and oriental topaz (yellow corundum) "may bo very similar in colour, 

 but the three species are readily distinguished, as seen in the table, by differences 

 in hardness and specific gravity. The colour of the topaz when examined in the 

 dichroiscope is often different in throe different directions, and may thus present a pale 

 straw-yellow, a pale honey-yellow, and a reddish yellow. 



Green Gems. 



Emerald S.G. 27 H. 8 D.B. 



Chrysolite ,,3-3 6'5 D.B. 



Tourmaline 3-0 7'5 D.B. 



Oriental emerald , . . 4 ,,9 D.B. 



