OCCLUSION OF IGNEOUS ROCK 403 



Biotite is also distributed in aggregates of large, coffee-brown 

 scales, intermixed with a little finely granular magnetite. The 

 folia of all these dark minerals show curvature in places as from 

 pressure ; so also the twinning bands in some feldspar grains. 

 Order of paragenesis — bronzite and enstatite, zoisite, brown 

 hornblende, plagioclase, pale amphibole, tremolite with mag- 

 netite, quartz, biotite and chlorite. No epidote, olivine or dial- 

 lage was distinguished. 



The other specimen, No. 109, is a still coarser quartz-gabbro- 

 diorite, resembling but not quite so coarse as some gabbros of 

 St. John, New Brunswick, and approaching the facies of a coarse 

 norite of the Cortlandt series. Feldspar for the most part dull 

 white, by incipient decomposition, intermixed with much white 

 and gray quartz. The black ferromagnesian mineral, apparently 

 hornblende, is largely distributed in rude prisms, often over 3 

 centimeters in length and 8 to 1 5 millimeters in breadth. 

 Brownish black biotite is abundant, in part rendered brassy yel- 

 low by decay. No bronzite appears to the eye, but many grains 

 of garnet, up to 6 mm. in diameter. 



It has been a disappointment not to have been able personally 

 to verify the character of this outcrop in place, to make sure 

 that the two specimens had not been taken from half-buried 

 transported boulders. But there are, at least, two earmarks re- 

 vealed in the microscopic structure of No. 107 which are 

 not in favor of that view : one, the form of the zoisite in 

 isolated crystals, as found throughout the diorite-schists of the 

 island, and not of the saussuritic character common else- 

 where ; the other, the alteration rim of colorless amphibole 

 (tremolite?) around bronzite and hornblende, a feature yet de- 

 tected only in the gabbros of Delaware, and never any farther 

 northward. Similar double fringes of uralite, tremolite and 

 bastite around grains of diallage,^ and of tremolite and actino- 

 lite around grains of hypersthene and diallage,^ of bronzite and 



1 L. Finckh, Zeits. d. d. geol. Ges., 1898, 94, 98, loi, 115. 



2 Strang, N. Jhrb. f. Min., 1862, 943, 948,950; J. H. Kloos, N.JIirh.f. 

 Min., Ill, Beil.-Bnd., 1884, 24-33 ; G. H. Williams, Bull. No. 28, U. S. Geol. 

 Surv., 1886, 40-45 ; F. D. Chester, loc. cit., 23-25; A. G. Leonard, Am. Geo/., 

 VIII, 1901, 15. 



