found in the Neighbourhood of Glasgow. 417 



Labradorite, as the name implies, was first noticed on the 

 coast of Labrador. It is of a dark smoke-gray colour, and 

 in particular positions reflects a variety of colours, blue, green, 

 yellow, red and brown. The crystals approach those of fel- 

 spar, but differ a little in the measurement of the angles. The 

 constituents are silica, alumina and lime, with a trace of soda. 

 The presence of lime distinguishes it from albite ; and the 

 proportion of silica is much smaller. 



Felspar is 4 Al S 3 + K S 3 



Albite 3 A1S 3 + NS 3 



Labradorite 3 Al S 2 + (f Gal + -1 N) S. 



I think it unnecessary to mention mica, epidote, steatite, 

 iron pyrites or carbonate of iron, which constitutes so abun- 

 dant a mineral in this neighbourhood. Nor is it necessary to 

 give an account of the gray ore of manganese which has been 

 met with, though sparingly, in die hills in our neighbourhood. 

 But there are two species of minerals which I believe to be 

 peculiar to the range of hills in our district, and which, there- 

 fore, deserve to be described. These are Kilpatrick quartz, 

 and sulphuret of cadmium, or Greenockite, as it has been 

 called. 



1. Kilpatrick quartz. This variety of quartz occurs in the 

 amygdaloid of the Kilpatrick hills. 



It is white and translucent, and constitutes spheres about 

 the size of a hazel-nut, mixed abundantly with stilbite and 

 calcareous spar. The spheres constitute an aggregation of 

 crystals ; the exterior termination of each, examined by the 

 microscope, is a four-sided prism. The hardness is the same 

 as that of common quartz; but the specific gravity is 2' 525, 

 while that of common quartz is 2*690. It contains 3 per 

 cent, of water, according to the analysis of Dr. R. D. Thom- 

 son, who found also a trace of sulphuric acid ; while common 

 quartz is anhydrous. 



These differences seem to warrant the propriety of consi- 

 dering it as a peculiar species of quartz. The same mineral 

 exists in the mountains of Nova Scotia, which bear a striking 

 analogy with those in the neighbourhood of Glasgow, both 

 in their constitution and in the minerals which they contain. 



2. Sulphuret of cadmium. This mineral occurs along with 

 prehnite in an amygdaloidal rock at Bishoptown in Ren- 

 frewshire. It has also been seen on the Cochno burn on the 

 north side of the Clyde. It was mistaken for blende by the 

 mineral dealers in the neighbourhood. Lord Greenock ex- 

 amined it in the summer of 184-0, and showed to Professor 

 Jameson that it could not be blende. Mr. Connel subjected 



Phil. Mag. S. 3. Vol. 17. No. 112. Dec. 1840. 2 E 



