VAR CUXxt. 
SILEX  Petuntse. 
Feldspar and Petuntse. 
Class 2. Earth. Order 1. Homogeneous, 
Gen. 4. Silex. Spec. _ Petuntse. 
Dw. 1. Crystallized. 
Syn. Feldspath. Delisle, 2.445. Emmerl. 1. 226. 
Feldspar. Kirw. 3177. 
Feldspath. Hazy, 2. 590. 
Spatum campestre. Linn. 
Fexpspar is a very common substance, chiefly found in 
ageregates of various descriptions. It is observable in the 
granites which come from Aberdeenshire to pave the prin- 
cipal highways in this metropolis, and remarkable in the 
Moor Stone of Devonshire on London and Westminter 
bridges, where the imbedded crystals are very bold and 
distinctly seen, especially after rain. The present speci- 
* men comes from near Monymusk in Aberdeenshire, by 
favour of my kind friend Mr. James Reid. The crystals, 
being nearly independent, allow us to see their determined 
form distinct from the gangue, which is more confused 
Feldspar with Quartz and dark crystallized Mica, forming a 
Granite. The little middle figure was easily detached, and 
makes a short six-sided prism. I haye put a geometrical 
