STURGEON QUAETZITE IIST FELCH MOUNTAIN EANGB. 403 



from 0.05 to 0.75 mm. in longest dimensions, but few, however, exceeding 0.2. 

 Many of these are bent and split, the clear unstrained quartz of the host pene- 

 trating from the frayed edges into the interior between the partly separated 

 leaves. Biotite and muscovite, and sometimes chlorite, occur in the same 

 individual, indicating alteration before inclusion in the quartz host took 

 place. Besides its common occurrence as an alteration product of the 

 biotite, a few rounded areas of chlorite, made up of little radiating tufts, 

 seem to be pseudomorphs of garnet. Inclusions of titanite and magnetite, 

 or a related ore, are not uncommon in the larger micas, and the biotite and 

 chlorite sometimes inclose beautiful sagenite webs. Many of the smaller 

 micas, however, have clear sharp edges and depart from the g-eneral paral- 

 lelism of the other inclusions. These are either contemporaneous crys- 

 tallizations or else, perhaps, were primary inclusions in former grains of 

 clastic quartz which has since disappeared. Some of the clastic plates of 

 biotite are bleached and include spheroidal blebs of red iron ore, similar to 

 those described in the case of the Archean mica-schists. 



The microcline inclusions are usually elongated in form, and frequently, 

 particularly m the cases of the larger, have well-rounded clastic outlines. 

 The long dimension, which usually coincides with one of the cleavages of 

 the mineral, rarely exceeds 0.5 mm. or falls below 0.08 mm. The periphery 

 is frequently partlj^ surrounded by a thin film of biotite. Within the micro- 

 clines are sometimes contained little blebs of quartz, which are not oriented 

 optically with the host, and also, more rarely, small plates of biotite. The 

 microcline individuals are sometimes broken into two or three differently 

 oriented parts, which may be separated from each other, in which cases the 

 quartz of the host has completely filled the interspaces. Fracture in the 

 feldspar is often unattended with the slightest ap^oearance of strain in the 

 inclosing and cementing quartz, Avhich extinguishes as one individual, and is 

 therefore unmistakably to be attributed to stresses previous to the crystalli- 

 zation of the quartz. 



Besides microcline, both orthoclase and plagioclase are sometimes 

 inclosed in the large quartzes, but much more sparingly. They are invari- 

 ably more or less decomposed, and are sometimes surrounded partially or 

 wholly by a film of ferruginous material. They show the same phenomena 

 of fracture, and occasionally of separation with penetration of the host, as 

 the microcline, and occur in grains having a similar range in size. 



