Vol. 70.] OF THE COUNTRY AROUND HUXTLV. 279 



IV. Coxtact-Metamorphism. 

 (a) The Foliated Rocks. 



As a whole, the foliated crystalline rocks of the area have been 

 little affected by the intrusion of these later igneous masses. At 

 Cairnford Bridge, the evidence of contact-metamorphism in the 

 phyllites increases rather to the west — that is, away from these 

 intrusions and towards the foliated intrusions mentioned above 

 (p. 267). The same is true, to some extent, of the exposures 

 along the Cairnie Burn near Gilgatherbush Bridge. Contact- 

 effects due to the later intrusions are, however, met with in Bin 

 Wood south of the Cairnie Burn and the Church, and in Cumrie 

 Plantation. On the south, very similar rocks are found near Ward 

 and on Cairnhill. 



Somewhat different rocks, occurring along practically the 

 same strike south-west and north-east of the area, are found on 

 Clashmach Hill and on Fourman Hill. There the andalusite-mica- 

 schist of the district to the south and west is met with : this, 

 having regard to its mode of occurrence, may be the result 

 of antecedent thermal metamorphism. On Clashmach Hill, this 

 rather sandy rock was found to be largely composed of quartz- 

 grains and biotite-flakes, together with some muscovite. The 

 andalusite, as in the case of the similar type described from Buck 

 of Cabrach by Dr. J. J. H. Teall, 1 occurs in large micropcecilitic 

 crystals with inclusions of small biotites and quartzes. G-arnet is 

 also present. 



In the type occurring on Fourman Hill at Kitty Callin, there 

 are the same dominant minerals, but the place of andalusite may in 

 part be taken by cordierite, which also occcurs in large poecilitic 

 crystals, enclosing quartz and biotite and showing numerous halos. 

 With the andalusite also occur numerous small staurolites, often 

 twinned. 



The phyllite of the district, as seen west of the footbridge at 

 Cairnie Church and near Cairnford Bridge, consists of quartz, 

 biotite, and muscovite often containing sillimanite-needles, with 

 occasionally a little garnet, and felspars both twinned and un- 

 twinned. The garnet may be anterior to the folding, as suggested 

 by the behaviour of the biotite-flakes that bend round the resistant 

 grains. 



Close to the junction with the later intrusions, rocks are found 

 containing abundant garnet, sillimanite, cordierite, and biotite, the 

 last-named preserving in its arrangement the original foliation. 

 The sillimanite is, with one exception, of the fibrous variety, and 

 is mainly associated, in tufts of highly-refracting needles, with 

 the biotite. Such tufts occur in most of the rocks from Cumrie 

 Plantation and from the neighbourhood of Ward, Avhile they are 

 well developed in the rock forming the top of Cairnhill. The 



1 Mem. Geol. Surv. Scot. 1896, Explan. Sheet 75, p. 36. 

 Q. J. G. S. No. 278. u 



