'% med, oor ‘Prof. F. of a fine grained passer | 
% ie a 
1 ge De 
212 Notices of the Geology and Mineralogy of Sicily. 
various minerals,which are ali derived from primitive rocks, 
se are ; 1. Feldspar, the most abundant, varying in 
size from minute threads and scales to distinct prism sand 
tables.—In some lavas of the middle age they form more 
than a third of the mass. 2. Black Pyrowene, equally 
abundant, entire, or in fragments. —3. Chrysolite (olivine) 
green or reddish ; the latter colour ee haha the more 
violent action of heat, as they are of a deep red in the 
porous Javas and scori#.—Abbe I", thinks they ought 
tone bat not of caval | ormation 
currents near Paterno, there are yellow and black seales of 
Mica, No Leucite is mentioned by Prof.F.as occurring in 
the lavas of AEtna. These crystals preserve their form 
and brilliance perfectly in the compact lavas but are more 
or less altered in the porous. The lavas of all ages are 
either compact or setae owing to the different degrees of 
heat to which they were exposed ; varying in this respect 
from the most empact trap- like lava to the lightest 
Poth and even passing from one to the other on the same 
yecimens. - Scorixe, sand, and ashes are all formed of the 
’ paste with the most compact lavas, only altered by 
; ter — of heat or mechanical violeace—Com- 
e easily compared with the analogous miner- 
5 ey a by fire. The crystals in the Javas are looser, 
_ the feldspar in the porphyritic lavas is more distinct in its 
outlines, less brilliant and drier. The lavas are also more 
sonorous, fusible and magnetic. In the ancient lavas near 
, there are aastoney Black Glass; (Obsidian) 
