Mineralogy and Geology of the White Mountains. 117 
seemed to be undergoing this change, we must look for another 
and more silent cause. This must be found in frost, moisture, 
&c., operating especially upon the large proportion of feldspar, 
the alkali of which is removed, and the mass is thus rapidly dis- 
integrated. The masses exfoliate on their angles and curves, and 
it is not uncommon to meet with those that seem to be affected 
by what Dolomieu calls la maladie du granite, which, on being 
struck with a hammer, fall entirely in pieces or grains. The ex- 
tent of this process may be imagined from the fact, that from 
Bartlett to the Notch, (nearly thirty miles,) the surface of the 
ground (as cut by the road ditches) seems entirely made up of 
decomposed feldspathic granite sometimes to the depth of two feet. 
Octahedral Fluor Spar. 
. Half a mile above the tavern of the elder Crawford, in the 
ruins of a slide east of the Saco, this rare mineral is found, which 
was mentioned twenty eight years ago in Bruce’s Mineralogical 
Journal ;* but the difficulty of obtaining specimens is much less 
than formerly. The spar is found in masses of radiated quartz, 
easily broken ; and occurs in pale green octahedra, from one fourth 
of an inch to one inch and one fourth in diameter, but is easily 
fractured in breaking the gangue; it phosphoresces most beau- 
tifully, on hot iron, with at first a yellowish light, which be- 
comes finally of a peach blossom color. On ascending the gorge 
about five hundred feet, (here about ten feet wide,) the quartz is 
found in place, on the south side of it, in close contact with the 
granite, which on the other side is removed, forming a vein or 
dike, (for it is really one,) two feet wide, and continuing farther 
up the mountain.’ Its structure is drusy, and there is near the 
middle a double serrated line, formed by the interlocking of quartz 
crystals. By unknown causes, the fluor has been in many eases 
partially or entirely removed, and the cavities thus formed are now 
filled with quartz in plates and crystals. Such a phenomenon in 
calcareous rocks and veins would be easily explained. The 
fissure existing, the calcareous matter in solution is deposited on 
either side, till the drusy surfaces unite in the middle. What 
greater difficulty in applying the same solution to deposits of sili- 
ceous matter in veins? The fluor is not equally disseminated 
* Mineralogical notice yo isin American fluates of Lime: by the Editor. 
Bruce’s Min. Jour., p. 33, Jan 
