180 MINERALOGY OF THE LIZARD DISTRICT. 



the quarry, about ^o-feet from surface. I think that had each been 

 obtained from similar depths, they would have been of nearly equal 

 specific gravity. Further, the sheet and banded matter compare very 

 favourably with my road metalling test in hardness and tenacity, 

 but under the microscope I have not yet discovered in the banded 

 rocks a single felspar retaining its original form or brilliancy. All 

 appear fragmentary and opaque, but showing evidence of being 

 equally as ready to give place to hornblende as their more brilliant 

 and perfectly formed neighbours in the adjoining gabbros. Augite, 

 enstatite, and olivine are found in a little better state of preservation, 

 but these, too, are giving place to new forms. 



Fig. 9 plate A, from Porthallow, shews serpentine after olivine, 

 and also contains a crystal of enstatite partially changed into 

 serpentine. Where the change has taken place it has the appear- 

 ance of matter as if it had been held in solution, but there is no 

 evidence that a solution had passed along a fault or fissure, as the 

 fibres of enstatite shew neither curvature nor breakage. From 

 Shepherd's quarry, was taken the beautiful specimen of malacolite 

 shewn in fig. 1 1 plate C ; it is changing into dark green hornblende, 

 and is associated with saussurite and actinolite. 



At Porthallow, from a grey band associated with serpentine, 

 was obtained the specimen shewn in plate C fig. 12, which consists 

 principally of hornblende and asbestus. It has the most perfect 

 anthophyllite crystals that I have yet seen, which were doubtless 

 derived from a similar change to those in the gabbro of St. Keverne. 



In 1886 I first noticed malacolite, or colourless augite, near 

 Kynance Cove, Porthoustock, and Porthallow, and about two years 

 ago Mr. Teale recorded his discovery of it at Karakleus,* since 

 which Gen. Mc Mahon has also found it, as he says, unexpect- 

 edly, at Penvoose, and remarks that, in certain sections, "Malacolite 

 may be seen, in thin slices, in every stage of conversion into horn- 

 blende, "f The finding of this igneous mineral in these different 

 localities, is, I think, sufficient to certify its presence in the whole of 

 the Lizard district, and, taken in conjunction with Prof. Judd's 



* Journal of the Mineralogical Society, No. 37, 1888. 

 tQuar. Jour. tteo. Soc, 1889, page 524. 



