Structural geology . Photomicrographs showing the progressive granulation of the Mnrinanorthosite under the influence of pressure. After Adams. GNEISSIC STRUCTURE SO These criteria may often be decisive whenapplied collectively, but seldom when used separately. They arediscussed on a subsequent page (97). Gneisses have been known to develop by rock flowage fromOcks which under other conditions have yielded schists. What, r. 43. Photomicrograph of leaf gneiss from the Laurmtian area north of Mon-treal. Slide furnished by Frank D. Adams. Doctor Adams has described theleaf gneiss as
Structural geology . Photomicrographs showing the progressive granulation of the Mnrinanorthosite under the influence of pressure. After Adams. GNEISSIC STRUCTURE SO These criteria may often be decisive whenapplied collectively, but seldom when used separately. They arediscussed on a subsequent page (97). Gneisses have been known to develop by rock flowage fromOcks which under other conditions have yielded schists. What, r. 43. Photomicrograph of leaf gneiss from the Laurmtian area north of Mon-treal. Slide furnished by Frank D. Adams. Doctor Adams has described theleaf gneiss as resulting from granulation of a hornblende granite, all stages ofthe process having been noted. (See Part J of Vol. VIII of the GeologicalSurvey of Canada, 1895.) The striated feldspars have irregular angular shapessuch as characteristically result from granulation. The two hands of quartzcrossing the slide evidently owe their form and arrangement finally to re-crystal-lization, although granulation may have been an important initial will be noted that the quartz individuals have dimensional but not crystal-Iographic parallelism. then, are the conditions which determine whether the gneissicor the schistose structure will result from the rock in question?Study of all analyses available of schistose and gneissic rocks 1 Trueman, J. D., The value of certain criteria for the determination of the originof foliated cr
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