ASSOCIATED ROCKS OF THE LIZARD DISTRICT. 905 



unaltered olivine ; but I think I have detected a few pseudomorphs. 

 This rock, then, is a basalt only slightly altered. 



The gabbro veins continue to the eastern side of the cove. One, 

 which shows a marked schistose structure, contains, as usual, many 

 long strips of serpentine. Close by it is another gabbro vein, only 

 a few inches thick, but quite uuique in character. It consists 

 mainly of felspar, a whitish to bluish-grey labradorite, with crystals 

 often from an inch to an inch and a half long, in excellent preser- 

 vation. In the interstices of the felspar are aggregated minute 

 crystals of a dull green mineral. The latter under the microscope 

 proves to be actinolite. The aggregated clusters of crystals are 

 very beautiful objects with polarizer and analyzer; and the felspar 

 crystals (which are a little decomposed) contain, especially near 

 their edges, man}^ small acicular crystals of the same mineral. 



Close to this vein is a small dyke (6 to 12 inches wide) of a very 

 slaggy-looking, compact, dark rock, which, I have no doubt, is an 

 old basalt. Some of the serpentine near this weathers to a dull 

 green colour, and contains distinct crystalline grains of magnetite. 

 Beyond this point is about a mile of coast, coloured as serpentine in 

 the map, which I have had to pass over almost unvisited ; and the 

 steep cliffs will, I think, render detailed examination no easy 

 task. 



(b) Coverack Cove. — We then come to Coverack Cove, one of the 

 most interesting localities on the coast. Without a regular survey 

 and large-scale map it is not possible to give very precise details ; 

 but the following general description may render clearer those which 

 I can furnish. 



The cove terminates in a widish valley. On the right bank is a 

 headland of serpentine, on the left the great gabbro mass which 

 rises from the sea to the upland of Crousa Down. 



The village stands on a low cliff (a raised beach, traces of which 

 are also conspicuous along the edge of the gabbro mass) on the right 

 bank of the cove. Beneath it is a rocky foreshore. 



The principal rock beneath the village is serpentine ; but this is 

 broken up by a network of dykes and intrusive veins. As will be seen 

 from what follows, we have here the following association of rocks 

 in order of age : — 



(1) Serpentine (no. 12). 



(2) A gabbro, generally of a dull reddish green colour, which I 

 shall refer to as the Older Gabbro. 



(3) A gabbro of more normal aspect, which I shall call the Newer 

 Gabbro. 



(4) Some dark trap dykes, similar in general appearance to those 

 described at Kennack and Lankidden. 



At the eastern end of the village is a small harbour bounded by 

 a pier, which starts from a little headland. I commenced my ex- 

 amination on the further side of this. The rock here is serpentine, 

 much jointed and cracked, and often rather decomposed. This is 

 also found on the other side of the harbour, where at the base of a 

 high wall a vein of gabbro is exposed, about 4 feet thick and with a 



