252 PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 
As black lead has been wrought at Rothiemay, Huntly, and other spots 
along the strike of these rocks, the “dead” here was doubtless also graphite. 
The bed of labradorite is the largest mass of that substance that I know of; 
it has generally been considered Saussurite. 
It contains imbedded many minute crystals of olive-green talc, from which 
it is freed with much difficulty ; it also contains minute sphenes, small crystals of 
pyrite, and specks of a lustrous black mineral too minute to be identified (ilme- 
nite?). Rarely in its mass twin crystals, apparently of the mineral itself, lie 
imbedded ; these are somewhat higher in lustre than the general mass, probably 
from the reflection being from a more continuous surface than the general some- 
what saccharoid massive mineral; they were not striated. JAMESON, who paid 
only a hurried visit to Portsoy, describes this as a bed of marble. 
This labradorite is hyaline vitreous in lustre, and of specific gravity 
2° 672. 
25 grains gave— 

Silica, 13:01 
From Alumina, * 248 
13° 258 =~ oan 
Alumina, : c : } : 29 * 852 
Ferric Oxide, . : f , 3 128 
Magnesia, : ; ; : *612 
Lime, : é : : : 11 436 
Potash, 5» HOD 665 av. * 642 
Soda, Oo OLS Sear a bly? es, 4°214 
Water, : J : ‘ 3 “42 
100 - 336 
Indissoluble silica, 2°881 per cent. ; probable impurity, a trace of talc. 
From hyperitic Diabase. 
2. From the Cuchullin Range, Skye. | 
The specimens were given me by the late Principal Forsrs, as from 
Hart-o-Corry. The bulk of these consists of imbedded crystalline masses of 
a fine lustrous green augite, which weathers of a bronzy lustre, and hence has 
been considered hypersthene. The “felspar” is for the most part in such small 
ill-defined crystals that it might be called granular ; it was thought commonly 
to be Saussurite. The other constituents of the rock are magnetite,—per- 
vading it, and crystallised in octohedra in the rifts; Biotite in small quantity, 
a rare trace of chlorite (?), and according to JAMESON “ glassy actynolite.” 

