TRANSPARENT STONES 



573 



The density of topaz places it in a division apart from all the other stones of this group, 

 and it is further characterised by strong dichroism. 



11. YELLOWISH-BROWN STONES. 



Of the stones of this group, topaz, amber, and the yellow variety of quartz known as 

 citrine are of common occurrence. Amber feels warm to the touch, is very light and soft, 

 and when rubbed becomes strongly electrified, attracting to itself any light objects, so that 

 it can scarcely be mistaken for any of the stones with which it is here grouped. The means 

 whereby amber may be distinguished from resinous and glass imitations have been fully 

 described under amber and need not be repeated. 



Topaz and quartz may be distinguished by the difference in specific gravity alone, but the 

 greater hardness and stronger dichroism of the former furnishes additional aid in this direction. 



Sphene is less hard than is idocrase or epidote ; these may be distinguished from each 

 other by an accurate determination of their specific gravity. Epidote is characterised also 

 by very strong dichroism. 



12. YELLOW STONES. 



