Vol. 59.] 



THE T.TREE AND IONA MARBLES. 



95 



are usually dolomite, the finer material stains like calcite. Other 

 minerals include : — (a) Very abundant forsterite : the crystals 

 weather-out as brownish lumps on the surface of the limestone ; 

 under the microscope complete or partial serpentinization is character- 

 istically displayed, (b) Scarce colourless mica, tremolite, and sahlite. 

 (c) A few scattered grains of greenish-blue spinel : this mineral 

 was not observed at any other point, and even here occurs in very 

 limited amount. 



(4) A white marble from the small quarry in the same field 

 (fig. 4). — This rock is generally similar to the last-described, but is 



Fig. 4. — Limestone similar to that of Jig. 3, but of finer grain and 

 well-foliated. From a small quarry in the same field. (About 

 -i not. size.) 



.■-..- 



Ethel M. Coomaraswamy photo. 



[The small augen consist usually of forsterite.] 



finer-grained and more compact, and conspicuously foliated. The 

 silicates, are forsterite and sahlite, which appear as ovoid augen, 

 round which the foliation sweeps (fig. 4), giving quite a gneissose 

 aspect to the rock. , , 



Various inclusions are characteristic of the Balephetrish marbles. 

 They may be classed as (1) gneiss-inclusions, and (2) mineral- 

 aggregates. 



(1) Gneiss-inclusions.— These occur in the pink marble at 

 Balephetrish, and in similar marbles on the shore west and north- 

 west of Balephetrish. The minerals characteristic of these inclusions 

 include quartz, felspars, hornblende, augite, scapolite, and sphene. 



