Silrceous Genus. 145 



I. VARIETY* 

 Quartz and ShoerL 



This ftone confifts of diftincT: grains of 

 each compared together in various propor- 

 tions. The quartz is generally white* or 

 reddifh; the fhoerl, black, brown, white, or 

 green : by fome it is called a granite. Some 

 of the paving-ftones of London are of this 

 fort* 



II. VARIETY. 

 Quartz and Fdt-fpar. 



The quartz is generally white ; the felt- 

 fpar red, yellow, or brown : found in the 

 Alps by Mr. Sauffure, from whofe excellent 

 work many of the following defcriptions are 

 taken. MilKiones and whet-flones are often 

 of this fort. 



III. VARIETY. 

 Jade and ShoerL 



The fhoerl is interfperfed through the jade ; 

 in a ftrong fire it rnelts, but the jade only 

 whitens. Saujfiire Voyage dans les Alpes^ p. 

 84. Its fpecific gravity is from 3*318 to 

 3,389. The jade is yellowifh, the flioerl 



green or black* 



IV, VARIETY. 



