. Annual report. New York State Museum; Science; Science. ELIZABETHTOWN AND PORT HENRY QUADRANGLES 123. Fig. 28 Old Bed ore. The blackis mag- netite; the stippled mineral is apatite; the lined mineral is emerald-green pyroxene. Actual field inch. The great ore body lies beneath a cap of this very acidic rock. The " 21 gneiss " appears at times at other horizons in the series but it is not always accompanied by ore. It is moreover very similar to the wall rocks at Hammondville, if not actually identical with them. Beneath the ore appears a more basic variety, rich in hornblende, a
. Annual report. New York State Museum; Science; Science. ELIZABETHTOWN AND PORT HENRY QUADRANGLES 123. Fig. 28 Old Bed ore. The blackis mag- netite; the stippled mineral is apatite; the lined mineral is emerald-green pyroxene. Actual field inch. The great ore body lies beneath a cap of this very acidic rock. The " 21 gneiss " appears at times at other horizons in the series but it is not always accompanied by ore. It is moreover very similar to the wall rocks at Hammondville, if not actually identical with them. Beneath the ore appears a more basic variety, rich in hornblende, augite; and sometimes in biotite. Plagioclase is abundant and inas- much as massive gabbro is seen beneath the Barton Hill ore, the basic gneiss was believed to be a metamorphosed representative of it and was called " ; Meantime, however, we have learned much regarding the syen- itic series of the Adirondacks and have also obtained some thou- sands of feet of drill cores not previously seen. From the latter it is evident that representatives of the former are the chief mem- bers in the series. Many more slides of the supposed " gabbro- gneiss " serve to ally it with basic developments of the syenite series and it is much more defensible to consider the ores as lying between the two extremes, an acidic and a basic, of the great syenite series. In the basic we find so much microperthitic orthoclase that it is practically impossible to draw sharp lines of distinction among these varieties when starting from the normal syenitic type. In the early paper a band of acidic gneiss was identified in the hanging wall of the Barton Hill group, and was called the " Orchard gneiss " after one of the pits. The rock was composed essentially of quartz and plagioclase with now and then a few magnetites and zircons. One related occurrence had microcline. This must be regarded as essentially a phase of the " 21 gneiss," since in the one case the
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