The geology of Ascutney Mountain, Vermont . O in the analy-sis suggests that it is a lepidomelane. Titanite is beautifully crystal-lized with the ordinary rhombic outlines and well-developed prismaticcleavage. Its pleochroism is strong: a, pale yellow. b, yellow. c, reddish ;b>a. Pseudomorphs of magnetite (ilmenite?) after titanite are not uncom-mon. In one out of seven slides made from this rock a single smallindividual of pale-green amphibole was discovered. Augite failsentirely. Here, as in the other stock rocks of the area, the quartz isrich in liquid and gaseous inclusions a
The geology of Ascutney Mountain, Vermont . O in the analy-sis suggests that it is a lepidomelane. Titanite is beautifully crystal-lized with the ordinary rhombic outlines and well-developed prismaticcleavage. Its pleochroism is strong: a, pale yellow. b, yellow. c, reddish ;b>a. Pseudomorphs of magnetite (ilmenite?) after titanite are not uncom-mon. In one out of seven slides made from this rock a single smallindividual of pale-green amphibole was discovered. Augite failsentirely. Here, as in the other stock rocks of the area, the quartz isrich in liquid and gaseous inclusions and in negative crystals arrangedin lines and also provided with double bubbles of gas immersed inliquid. The order of crystallization is the normal one: 1. Titanite, apatite, zircon, and magnetite. 2. Lepidomelane. 3. Albite and ortlioclase. 4. Microperthite. 5. Quartz. The essential oxides (see Table X, col. 1, p. 84) and their molecularproportions are noted in the following table: SiO^. AI2O3 Fe^Oa FeO- MgO CaO. Na,0 K2O- TiO., ZrO, P, Molecularproportions. If all the Ti02 be ascribed to titanite, and if we assume that themica contains 10 per cent MgO, 8 per cent KjO, and 40 per cent SiOg,Bull. 209—03 6 82 GEOLOGY OF ASCUTNEY MOUNTAIN, VERMONT. [bull. 209. the analysis may be calculated and the quantitative inineralogicalcomposition determined, with small degree of error, as follows: Per cent. Albite molecule Orthoclase molecule Quartz . Anorthite molecule _ _. Biotite -. - Magnetite . Titanite Apatite Zircon Chemically, this rock is an ideal equivalent, among the alkalinerocks, of granite among the nonalkaline eruptives, a biotite-granitecharacterized by a high total of alkalies with the soda and potash innearly equal proportion. Iron, lime, and magnesia are all low. It isagain to the Christiania region that we must go for the alreadydescribed type nearest to
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