PHYSIOGRAPHY. CLASS n. 



cularly common Quartz, are found in pebbles. The 

 river sand, and that of many extensive plains, consists of 

 the latter, and is often so fine as to be drifted by the winds, 

 llhombohedral Quartz frequently fills up the space of 

 petrified bodies, as, for instance, echinites in chalk, and 

 petrified wood in sandstone and in alluvial deposits. 



5. The numerous varieties of the present species are 

 spread all over the globe, but some of the most distinguish- 

 ed varieties are found only in a few localities. The finest 

 and largest Rock-crystals of high degrees of transparency 

 are found in the alps of Salzburg, the Tyrol, Switzerland, 

 Dauphiny, Piedmont, and Savoy, also in the isle of Mada- 

 gascar, Ceylon, and Brazil. Several varieties from Hun- 

 gary and Siberia are pale violet-blue, some called Smoky 

 topaz) from Bohemia, brown and yellow. The Scottish 

 Cairngorm sometimes possesses several bright tints of 

 these colours, in one and the same specimen. Ame- 

 thysts of various colours are brought from Brazil, but 

 he finest violet-blue colours come from Ceylon, India, and 

 Persia, where some of them are found in pebbles. Less 

 transparent or well coloured, they occur in original reposi- 

 tories at Porkura, and other places in Transylvania, in 

 Hungary, Siberia, &c. Some varieties are also found in 

 Scotland, in Saxony, in the Hartz, in Bohemia, in Silesia, 

 &c. ; and they are met with in veins, in agate balls, or in 

 secondary deposits. Rose-quartz occurs at Rabenstein near 

 .Zwiesel in Bavaria, and in Siberia ; the milk-white varie- 

 ties of it are known from Norway, Spain, France, &c. 

 The locality of Prase is Breitenbrunn, in the mining dis- 

 trict of Schwarzenberg in Saxony. Smalt-blue calcedony 

 sometimes crystallised, occurs at Tresztyan in Transylva- 

 nia, the stalactitic and reniform shapes occur in fine varie- 

 ties in Iceland and the Faroe islands in amygdaloid, at 

 Hiittenberg and Loben in Carinthia, in beds of iron- 

 stone : also in Hungary, Transylvania, in Scotland, and 

 other countries. Most beautiful and elegant specimens 

 have been found in Trevascus mine in Cornwall. Carne- 



