376 ME. CLOTJGH AND DR. POLLAED ON SPINEL [Aug. 1 899, 



noticeable that rocks of different characters lie next to the quartzite 

 in different places, and, in one or two localities, the alteration- 

 products which characterize the limestone are found in contact with 

 the quartzite, though in other places there are distances of several 

 hundred yards between the quartzite and the nearest exposure of 

 limestone. 



In all the exposures of limestone we are at once struck with the 

 great number of pieces belonging to different silicates which project 

 from the calcareous matrix of the rock. There are masses of a 

 white augite — called diopside by Mr. Teall — which sometimes 

 attain a breadth of several yards. Smaller lumps of this mineral, 

 and pieces of some serpentine-like mineral, are so abundant that, 

 taken together, they may equal the rest of the rock in quantity. 

 The pieces of diopside are generally edged by a narrow rim, often 

 about J inch thick, of some dark green, serpentinous substance. A 

 thin slice (7918) was prepared for the examination of this sub- 

 stance : no pieces resembling olivine were found within it, and 

 Mr. Teall states ' that it is not possible to determine with certainty 

 the minerals out of which the serpentine has been formed.' Some 

 of the smaller pieces of diopside project several inches beyond the 

 calcareous matrix, and are only connected with it by narrow neck- 

 like constrictions ; these pieces remind us somewhat of the sponge- 

 like forms which occur in certain portions of the altered Durness 

 Limestone of Strath Suardal (Skye). 



Small flakes of mica, pale yellow macroscopically, are rather 

 abundant, and in one locality, rather more than | mile east-north- 

 east by north-east of Bailamhuilinn, large plates of a similar 

 mica occur as much as 3 or 4 inches long, and full of inclusions 

 of calcite. This mica has been examined by Mr. Teall, and he 

 calls it phlogopite (7693). 



In several places the limestone has a banded appearance, as it 

 shows many parallel layers, from | to 4 inches thick, which 

 contain fewer of the serpentinous pieces than the rest of the rock 

 does. These layers are often twisted and contorted, and they are 

 occasionally seen to wind round lumps of the diopside. The 

 smaller serpentinous pieces, including perhaps all those which are 

 less than a hazel-nut in size, show no grains of diopside near their 

 centres, and they are honey-yellow, pale green, dark green, or 

 almost black. 



Thin strings of fibrous hornblende, either colourless or pale green, 

 are often found along lines of movement, and are sometimes seen to 

 traverse, and fault the sides of, the diopside-serpentine lumps. In 

 one locality there are needles of tremolite which have been folded 

 into a close succession of small V-shapes, and have been crossed 

 by lines of strain-slip. The mass of the limestone is, however, not 

 affected by such movements, and there can have been but few 

 deforming or mylonizing movements near the limestone since the 

 development of the minerals now characteristic of it. In this 

 respect the limestone offers a strong contrast to the limestone which 

 occurs in the Archaean rocks of Letterewe (Loch Maree). 



