20 NEW YORK STATE MUSEUM 



One can hardly avoid referring the development of these diopsides 

 and garnets to the influence of the neighboring anorthosite. The 

 mixture is indeed not unlike the original of the ophicalcites near 

 Port Henry (see Museum Bulletin 138, page 23), vi^here, however, 

 the mottled rock can not necessarily be referred to contact action. 

 At Cascadeville there is no passage to serpentine, but the diopside 

 is beautifully bright and fresh. Garnets have not yet been noted in 

 the ophicalcite. The geological relations are such as to suggest 

 contact effects for these two minerals, diopside and garnet, as they 

 are the most frequent of the lime-silicates in the undoubted zones. 

 Below the limestone the anorthosite is cut by several basaltic dikes 

 and contains a small exposure of magnetite. 



Contacts near Owls Head. The Grenville limestones appear in 

 a few ledges northwest from Owls Head peak just at the edge of 

 the quadrangle. From one of these a rather fine-grained contact 

 rock was gathered, which was almost as dense as ordinary horn- 

 fels. Under the microscope it proved to be about 70 per cent 

 golden brown garnet, 20 per cent emerald-green pyroxene, and 

 nearly 10 per cent quartz. The slide presents beautifully colored 

 minerals (see plate 11). There is also another mineral, of bright 

 aggregate polarization, which looks much like sericite as derived 

 from orthoclase. Anorthosite ledges are frequent in the vicinity 

 but the immediate contacts were not visible. 



Contacts south of Keene Center. In the improvement of the 

 highway along the east bank of the East branch of the Ausable river 

 and immediately beneath the word " East " on the map, three- 

 fourths of a mile south of its northern edge, a ledge was blasted 

 out in the spring of 191 o. The excavation brought to light a most 

 interesting assemblage of contact minerals. The hand specimen at 

 once revealed wollastonite and garnet, with diopside and calcite in 

 moderately coarse aggregates. Under the microscope the same 

 minerals appear with one or two others. Garnet in calcite is shown 

 in plate 12. The wollastonite is broken by its cleavages into finely 

 prismatic bundles, in the common sections, but when cut across shows 

 the characteristic cross-sections. The garnet, while pink in the 

 hand specimen, becomes pale yellow in the slide. It sometimes 

 alters as shown in the accompanying sketches to some more highly 

 refracting, almost opaque mineral in wormlike growths, which are 

 included in the garnet itself (see plate 13 A). They resemble 

 leucoxene more than any other mineral. The slides also contain 

 quartz and the aggregate mineral mentioned above under the con- 



