MODE I. QUARTZ. 149 



Grey granular quartz, from Balahulish, in Scot- 

 land. 



The same, with veins of white semi-transparent 

 quartz, from Bunessan, Mull. 



Saussure describes, 999, rocks of a beautiful 

 granular quartz, which rises in leaves of a rhom- 

 boidal form. It is very hard, and has the grain 

 and whiteness of statuary marble. 



He also observes, 2235, that in primitive lime- 

 stone there are often veins of quartz, as there are 

 also veins of keralite or hornstein in compact lime- 

 stone. Query, if both the latter substances do 

 not contain more argil ? 



Mr. Playfair observes that granular quartz is 

 common in Scotland, alternating with schisti, par- 

 ticularly on the north side of the harbour of Bala- 

 hulish, and on the sea-shore at Cullen. He also 

 shows that sand is a crystallisation ; and mentions 

 a siliceous grit with no cement*. 



,In Buckinghamshire, Wiltshire, and Dorset- 

 shire, where there are only sand and chalk, there 

 is found in the sand a prodigious number of large 

 blocks of granular quartz, which is used for paving 

 or building. The castle of Windsor, and the ter- 

 race, are built of this stone, probably from the 

 forest, or the neighbouring heaths, where there is 



* Hutt. Theory, 27, 171, &c, 



