SCHISTS OF THE LIZARD DISTRICT. 13 



a felspathic mineral, also of irregular outline, now replaced by micro- 

 liths of secondary origin, a good deal of green mica, and but little 

 hornblende. Minute enclosures are numerous in the quartz, some 

 being cavities. Bubbles, if indeed they occur, are very minute ; 

 ferrite, opacite, and a little epidote are present in -the slide. (3) A 

 dull-green, fairly fissile schist (p. 3), consists of hornblende in small 

 prisms, with the angles slightly rounded, ranging generally from 

 •001" to '005" in length, sometimes a little longer, but oftener 

 smaller, only one or two of which show cleavage-planes. It is of 

 a pale-green colour and moderately dichroic ; with this, often in 

 large plates, is a pale-green fibrous mineral associated with opacite 

 and ferrite microliths, doubtless an altered biotite. The quartz con- 

 tains included microliths of hornblende and ferrite, with possibly 

 some minute cavities. The minerals exhibit a wavy parallelism. 



(4) Compact rather quartzose green schist at the top of the Quadrant 

 Headland (p. 3) ; not very markedly foliated, consists chiefly of 

 well-marked quartz grains, with flakes and belonites of a pale-green, 

 rather fibrous, mineral. Some of this extinguishes as a mica, some 

 as a hornblende, so that we have a mixture of the two minerals. 

 The quartz is generally clear, with but few cavities and these very 

 minute ; microliths of hornblende (?) are sometimes present in them. 

 There is also a fair quantity of a peculiar earthy-looking mineral, 

 some of which may be epidote ; this also occurs in some irregular 

 divisional pianes cutting across those of foliation ; ferrite and opacite 

 are scattered about the slide, with a few small colourless garnets. 



(5) A rather compact, finely corrugated, dull-green schist from 

 beneath brownish mica-schist west of Polpeor (p. 3). This 

 consists of hornblende (abundant) in rather elongated prisms, 

 ranging commonly from about *01 inch long to mere microliths, 

 their longer axes roughly parallel ; quartz is mixed with this, and 

 here and there occurs in more distinct bands. Fluid- cavities are 

 present in this rock, varying much in size, and in some cases con- 

 taining bubbles ; these, it may be remarked, differ much in their 

 size relative to the cavity, occupying sometimes from *2 to -5 of its 

 whole volume. Some epidote, pyrite, haematite, and perhaps magne- 

 tite are present, with a kaolin-like mineral, probably replacing a 

 felspathic constituent ; the slide is traversed by cracks making a 

 high angle with the lines of foliation, which are crumpled up near 

 them, showing that the latter are due to a kind of cleavage 

 subsequently produced. (6) A rather compact green schist from 

 the headland just south of Polpeor (east side) has a general 

 resemblance to (3), but contains less quartz and more of a granular 

 earthy-brown mineral, probably replacing a felspar, which also 

 occupies some transverse cracks. (7) A rather olive-brown mica- 

 schist with silvery lustre, is a very pretty object under the 

 microscope. It consists mainly of quartz and mica ; the former in 

 well-marked clear grains, cavities and inclusions being rare and 

 minute. The mica occurs in wavy bands or divergent folia. Three 

 kinds are present, brown, green, and colourless. The first is pro- 

 bably biotite ; the second (often interbanded with it and containing 



