268 M. Beudant on the Pitchstone of Saxony. 
those >vliich occur beyond Freyberg, in all the hills around 
Kremnitz, and which belong to the red sandstone formation 
(formation des gres rouges). Above the baths, we begin to find 
the pi'tchstones, which present an infinite number of varie- 
ties. We observe all the transitions from rocks perfectly 
vitreous, and with a resinous lustre, to rocks entirely earthy 
(pierreuses), the greater number felspar, the others siliceous, 
presenting every tint of colour, brownish-red, reddish-white, 
greenish, &c. All of them, and especially the vitreous varieties, 
include crystals of lamellar felspar, more or less numerous, 
which are even occasionally a little split, and resemble glassy 
felspar. We find also, but very rarely, hexagonal lamellae of 
brown micaj having a great degree of lustre. In general, these 
ro6ks have the greatest analogy with certain varieties of obsidian 
(perlite), which we have observed in the Valley of Glasshutte. 
The only difference that I could observe, is, that here there was 
not the least indication of porous substances or pumice, nor are 
the nodules or globules radiated from the centre to the circum- 
ference, which are so common in the obsidian, to be seen either 
in the vitreous masses, or in the varieties which become earthy. 
But, if the Valley of Tribisch is extremely interesting as a 
place for studying all the varieties of which pitchstone is suscep- 
tible, it is not equally so with regard to the relative position of 
this rock. It is impossible, with reference to this, to determine 
any thing with precision. It might in general be supposed, 
from the mutual position of the masses, and the mineralogical 
relations which their different varieties present, that the clay- 
stone porphyries, and the pitchstones, belong to the same forma- 
tion, and that they both rest upon the dark-brown porphyries 
which constitute the principal mass of the country. Fortunate- 
ly, the relations are more distinct in other places, which are not 
so far removed from this as to^give rise to the supposition that 
the rocks belong to a different formation. The most remarkable 
locality is near Mohorn and Herzogswald. There pitchstones 
occur, which do not present a great number of varieties, but 
which evidently belong to an arenaceous deposit, the basis of 
which is a true claystone (argilolite), of a reddish colour, and 
very solid consistence. The fragments are of gneiss, mica^slate, 
and clay-stone. They are commonly angular, small, and more 
