304 MINERALOGY. 



«r Rock Crystal ; some of the combinations of Silex, aig 

 among the more valuable of precious stones, as the Amethyst, 

 Garnet, Opal, Agate, Lapis Lazuli, <^c. All these varieties 

 are met with either singly or in veins in mountainous 

 countries, frequent occurring in Mines of various Metals, as 

 Tin, Lead, Copperj &c« 



2. Alvmine. Is when pure, perfectly white, and without 



taste or smell ; like the preceeding, it is infusible except 

 by Voltaic electricity. 



Alumina enters into the composition of a large number of 

 Mineral substances, and is the base of Common Alum ; its 

 presence may mostly be detected by an odour which the 

 earthy substances with which it is combined, give out when 

 breathed upon, and which is usually termed the Argillaceous 

 odour, from Argilla, the Latin term for Clay, of which Alu- 

 mine is often a principal part. Alumine enters into the 

 composition of several stones in considerable estimation, 

 as the Oriental Ruby, Sapphire, Topaze, &c, 



3. Lime. In a natural state its colour is whitish, somewhat 



hard, infusible except by the Voltaic battery ; it enters 

 Into the composition of numerous earthy and stony 

 substances ; but has never been found pure. 



The various combinations of Lime are among the most 

 valuable, if not superior to all minerals as affording 

 substances of infinite importance to the Agriculturist, 

 the Manufacturer, and the Builder ; for general purposes 

 Lime is obtained by heat from a variety of Carbonates. 



