380 ORIGIN AND SUCCESSION OF LIZARD SCHISTS. 



and Saddleback. Gneiss occurs, sometimes exchanging its mica for 

 hornblende, on the east flanks of the southern parts of the Malvern 

 Hills, where it is much intermixed with dolerite. It may be regarded 

 as older than the Cambrian rocks. 



Schists of the Lizard, The serpentine of the Lizard district, 

 which has an intrusive aspect, seems to rise as a boss within a girdle 

 of schists. These schists, which form a single natural group, are 

 nevertheless divisible into three series, which Professor Bonney dis- 

 tinguishes as micaceous, hornblendic, and granulitic. The lowest 

 series consists of compact dull green schists and brown mica schists. 

 The middle group is formed of black hornblendic schists, which are 

 shining, and banded with felspar or epidote. The uppermost series 

 is formed by pinkish-grey rock, composed chiefly of quartz and felspar, 

 but banded with micaceous layers and seams of dark hornblende. 



The lowest group is well shown on the southern coast of the Lizard, 

 especially about the point called the Quadrant ; and in the next cove 

 there is a faulted junction between the micaceous series and the 

 hornblendic series. The hornblendic group is well shown in Houzel 

 Bay ; and at Hot Point the rocks show lenticular bedding, with 

 remarkable instances of false bedding and indications of ripple-drift. 

 These hornblendic schists are frequently rich in epidote, and some- 

 times have a granitoid character. At the bay under the Balk quarry, 

 where the first intrusion of serpentine is seen, the commencement of 

 the granulitic series is found. These rocks consist of distinctly strati- 

 fied beds of massive quartz, alternating with schistose bands. The 

 quartzite is sometimes felspathic, and occasionally contains a little mica 

 or hornblende, but the darker schistose layers are rich in these 

 minerals. Lenticular bedding and current bedding are rare in this group. 

 The hornblende schists are well developed on various parts of the coast, as 

 in Polurrian Cove, and on Pradanack Point, where the schists become 

 very massive, and in hand specimens resemble a diorite. Professor 

 Bonney calculates the maximum thickness of the whole series at about 

 3300 feet, of which rather less than three-fourths would belong to the 

 hornblendic group, and about 300 feet to the granulitic group. These 

 schists have lost their original structure, and many have become highly 

 crystalline, but the current-bedding appears to be preserved, especially 

 at Hot Point, although the constituents of the rock have undergone 

 a crystalline change. It is suggested that the metamorphic agency 

 softened the whole rock mass, so that the materials crystallised much 

 as they would have done had the rock material been igneous ; and in 

 places the unaltered or undigested rock remains, surrounded by 

 crystalline minerals which form granitoid bands. Professor Bonney 

 thinks that such hornblendic schists may originally have been 

 basaltic tuffs. Such an origin would explain the close correspondence 

 between some of the altered rock and diorite, which furnishes evidence 

 of unusual interest concerning the transition between the water-formed 

 and fire-formed rocks. The progress of metamorphism may have been 

 extremely slow, for the change consisted in the replacement of the 

 materials of the rock under conditions of pressure and crumpling such 



