Serpentiniie of the Lizard. 283 



roxene and hornblende. But we entertain a suspicion that the 

 porphyritic pyroxenic rock (a hard wackite) of Bufaure in the 

 Val di Fassa, Tyrol, which contains crystals of pyroxene of the 

 average size of the Cornish pseudomorphs, is a still nearer 

 counterpart. It must also be borne in mind that at Monzoni, 

 in the same region, porphyritic pyroxenite passes into serpen- 

 tine rocks, some of which contain crystals in various stages of 

 pseudomorphism, ending in perfect serpentine. 



The Lizard serpentine is not characterized with many struc- 

 tural varieties or allomorphs. Chrysotile, which is the only 

 one we are acquainted with, does not occur to any extent. 

 Thin veins of it, variously intersecting the serpentines, are to 

 be seen passing from amorphousness, through the incipient, 

 into the fully developed or normal condition. Fig. 3 repre- 

 sents a vein subdivided into three layers in different states : 

 a, layer of incipient chrysotile, whose substance, in being sim- 

 ply marked at distances (as in stylolitic structure) with faint 

 dark parallel lines, is still manifestly serpentine ; h, layer of 

 normal chrysotile, which is a mass of white glistening parallel 

 fibres, so infinitely divisible that it is impossible to determine 

 their form, any more than that of the fibres of asbestos, with 

 the highest magnifying-power *, 



As yet we have failed to detect any varietal examples of 

 chrysotile with a definite acicular structure, such as occurs 

 in many ophites, and more or less separated by films of caicite. 

 In one instance caicite is present in the layer c, but dividing 

 it in two halves. 



Its Methylotic Phenomena. 



Not only may it be assumed that the serpentinite of the 

 Lizard was originally a different rock which became methy- 

 losed, but we have every reason to believe that its essential 

 mineral constituent, in itself, has undergone further changes of 

 the kind. 



Many of our specimens, notably from Kynance Cove, in 

 addition to their various shades of green (from pale to nearly 

 black), show the serpentine gradually changing into brown, 

 pale yellow, and cream-colour. Often the change is manifested 

 by the serpentine becoming sinuously banded like chalcedony 

 in agates, the bands of different colours and various degrees of 

 lustre blending, or abruptly meeting, with the most beautiful 

 effect (fig. 4). This is heightened by the substance of the 

 bands occasionally appearing as if it had been in a gelatinous 



* Although the incipient and normal kinds of chrysotile may be dis- 

 tinguished from each other, as in the text, yet the one is occasionally con- 

 vertible into the other by mechanical appliances, as rubbing; Which 

 reminds us of double-refracting caicite, whose cleavage, to all appearance 

 nil, is developed by a blow of the hammer. 



