206 PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 
the silica insoluble was 4°054. The highest quality was that of steatite, from 
Scalpa, in Harris, 28°48 per cent.; the lowest that from the silica of orthoclase, 
from Froster-Hill, in Aberdeenshire, 027 per cent. The steatite was a very 
pure variety—the finest in Scotland—from a vein in serpentine. The ortho- — 
clase was from syenite,—it was neither fine nor characteristic i in appearance,— 
‘rather resembling oligoclase. 
In the 181 minerals, every kind of proportion of insoluble silica appears, up © 
to 14 per cent.—very few above that. 
So far for different minerals; but very different amounts appear we the @ 
same imninerals from different localities. 
I instance 
Orthoclase— * 
Froster-Hill, Aberdeen ; vein in syenite, : = : 027 per cent. insoluble. 
Glen Beg, Glenelg; from limestone, . 45 : *422 sn 
Glen Fernate, Perth; vein in mica schist, : , “Ho. = . 
_ Lairg, Sutherland ; syenitic granite, “205 a > 
Rubislaw, Aberdeen ; vein in granite, 
Struay, Ross; pink, layer of gneiss, 
Canisp, Sutherland ; from porphyry, 
Struay, Ross ; blue, : : he 
Tongue, Sutherland; vein in “syenitic granite,” 
Loch of Leys, Aberdeen ; layer of gneiss, 
Cowhythe Head, Banff; vein in talc slate, 
Corrybeg, Arran; from pitchstone, 
Ben Capval, Harris; vein in hornblendic gneiss, 
Kinkell, Fife ; crystals t in trap tuff, 
Cowhythe Head, Banff; vein in talc slate, 
being a difference almost as great as that of 1 to 690. 
ne 
lop) 
for) 
a 
0 
for) 
bo 
Saponite— 
Gapol, Kincardine; green, , ee : Sete ae “UO GT at Same 
Quirang, Skye; white, . . : : ol! Khao A if 
Do., -do.; yellow, . : : ° hye ORS OR). BE i ead 
ora difference equal to that of 1 to 410. 
Precious Serpentine— 
Portsoy, Banff; liveetehn veins, : ix 2 *485 b: 53 
~ Do.,  do.; chocolate-brown veins, : fee otal ss : 
the composition of the two being almost identical. 
' The two instances last cited show that different amounts are obtained from. 
the same mineral from one and the same locality. 
While, /asily, in examining the “ silicas” of the same mineral, the analysis 
of which was repeated, I have on some occasions obtained differences as great — 
as? tod: 
ve a a 


