118 Mr. W. Phillips on Cleavelandite. [Feb. 



Sulphate of Copper and Potash. 



The primary form is an oblique rhombic prism, and differing so 

 little from the preceding in measurement, that the same figure 

 may be used for both. The crystals do not appear to possess 

 any distinct cleavage. 



P on M, or M' 104° 30' 



P on e, or e' 154 20 



Pone' 116 20 



MonM' 107 35 



Monk 126 12 



Article X. 



On the Occurrence of Cleavelandite in the older Rocks generally. 

 By W. Phillips, FLS. &c. 



The discovery of cleavelandite as an ingredient in several 

 rocks of various and distant parts of England and Scotland, as 

 detailed in the Annals of November last, induced me to pursue 

 the subject further, from the notion that if this mineral should be 

 found only in particular descriptions of rocks, its presence, or 

 the contrary, might tend to throw some light on the difficult and 

 intricate inquiries connected with the comparatively relative ages 

 of the older rocks in general. 



With this view I have examined rocks of different countries, 

 and although the examination has been limited to two or three 

 hours each evening for three or four weeks, it appears to me that 

 sufficient evidence has been obtained to evince the probability 

 that the presence of this mineral is almost universal in the older 

 rocks, and that it will frequently be found accompanying felspar 

 in them. 



Of the rocks of Cornwall, the only one noticed in my former com- 

 munication was a porphyritic granite from Carnbrae ; I have since 

 found it intermingled with felspar, quartz, and mica, as the paste 

 of a porphyritic granite from Huel Gotland Mine, near St. Die, and 

 also in another from near the Land'? End ; in both the cleave- 

 landite is white and opaque, and the felspar translucent or trans- 

 parent. In a granite from Dartmoor, in Devonshire, consisting 

 chiefly of nearly opaque red felspar intermingled with hornblende 

 and quartz, the cleavelandite is translucent and slightly reddish, 

 and it bears but a small proportion to the felspar. It occurs 

 sparingly intermingled with felspar in the sienite of the Malvern 

 Hills. I have not succeeded in finding this substance as an 

 ingredient of any one of the numerous specimens in my posses- 



