. Bulletin of the Geological Society of America. Geology. THE GRANULITE OF KEENE TYPE LOCALITY. 257 Cross-section.—Figure 7 represents a section paced off in a brook near the largest mine. The strata dip westward toward the main range of hills and awa}^ from Keene valley. The black hornblendic schists are not lacking at neighboring exposures, but they do not show in the sec- tion which is made up of two bands of limestone separated and bounded by a dense garnetiferous rock. Petrography and Mineralogy—The Granulite.—In thin sections this garnetiferous rock is seen to contain in addition to garn
. Bulletin of the Geological Society of America. Geology. THE GRANULITE OF KEENE TYPE LOCALITY. 257 Cross-section.—Figure 7 represents a section paced off in a brook near the largest mine. The strata dip westward toward the main range of hills and awa}^ from Keene valley. The black hornblendic schists are not lacking at neighboring exposures, but they do not show in the sec- tion which is made up of two bands of limestone separated and bounded by a dense garnetiferous rock. Petrography and Mineralogy—The Granulite.—In thin sections this garnetiferous rock is seen to contain in addition to garnets untwinned feldspar, a little plagioclase, green augite and a little apatite ; no other minerals are present It is thus a granulite and closely analogous to the pyroxene-granulites of Saxony. The association of such rocks with limestones and iron ores in Sweden in similar relations to the above occurrence has been described* by Tornebohm. Despite the general lack of twinning, it would seem as if this untwinned feldspar must be, in part at least, plagioclase. Some twins do occur, but this is not true of. > granulite BREAK ANORTHOS/TE w 100YDS. vv Figure 7.— Cross-section near Weston Mine, Keene. the great majority of the crystals. Of these untwinned crystals the ex- tinction is often parallel to the cleavage, but it may reach 23 degrees. The microperthitic growths are ver}^ widespread. One crystal with two good cleavages was detected which gave an axial bar parallel to one of them and was shown by the quartz wedge to be negative. It must be orthoclase. Microchemical tests on another specimen yielded fluosili- cates of potash in considerable amount—of soda and of lime rather more. The conclusion is unavoidable that both orthoclase and plagioclase are present, the latter ranging as basic as labradorite. George Hawest showed years ago that twinning might fail in plagioclase, and especially in the labradorite of anorthosites. As this socalled granulite is regarded as
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