fO« On Gems. 



raid are frequently found inserted in the gangues of quartz^, 

 and even of fluor. 



Its specific gravity compared with that of water is as 

 27*753 to lO-OOO. 



The emeralds which come from America are called occi- 

 dental : Peru and the Brasils afford the most beautiful. 



The emerald melted in the furnace of Pott : it was spee- 

 dily fused by the mirror : oxygen gas fuses it in a white 

 milky bubble tinged with green. 



The emerald analysed by Vauquelin afforded 

 Silex . - - 64-60 

 Alumine - - 14*00 



Glucine - - 13*00 



Chrome - - 3*50 



Lime • - » 2" 56 



94-66 



The Topaz. 



The topaz is a precious stone of a fine golden yellow co- 

 lour. The oriental topaz takes the octaiidral form : the Bra- 

 silian crystallizes in rhomboidal tetraedral prisms, grooved 

 longitudinally : they are terminated by two tetraedral py- 

 ramids with smooth triangular faces. The Saxon topaz 

 exhibits long suboctaedral prisms, terminated by hexacaral 

 pyramids more or less terminated at their base. 



The specific gravity of the oriental is as 40* 106 to 10-000 ; 

 that of the Brasilian 35*365 to 10-000. 



The topaz is not fused in the porcelain furnace ; but both 

 the Oriental and the Brasilian are fused, and lose their colour 

 for a white opakc mass, by oxgen gas. 



The topaz analysed by \'auquelin gave 



Silex - - - 68 

 Alumine - - 31 



99 



The Hyacinth. 



The hyacinth is a stone of a fine reddish yellow colour ; 

 it is usually cryi-tallized in the form of a rectangular tetra- 

 edral prism, terminated by two quadrangular pyramids with 

 rhombic faces. 



Its specific gravity compared with water is as 36*873 to 

 10-000. 



It 



