SOME UNUSUAL ROCKS FROM MAINE 183 



The soda, having a stronger affinity for alumina than the calcium, 

 would appropriate it all in the production of albite, while the calcium 

 would be forced to combine with the iron and magnesia in the forma- 

 tion of diopside. 



III. A NEW OCCURRENCE OF CORTLANDITE 



In 1886 G. H, Williams^ described certain peridotites from the 

 Cortland series near Stony Point, N. Y., which were peculiar mainly 

 in the development of large hornblende crystals which served as 

 a poikihtic matrix for olivine grains. It was in the description 

 of these rocks that the term "poikilitic" was first applied. The 

 hornblende crystals occasionally reach a diameter of 4 inches, and 

 frequently show "schillerization." The olivine is usually very fresh. 

 Besides these two constituents, some hypersthene, augite, biotite, 

 and magnetite are usually present; -feldspar is sometimes an acces- 

 sory, but is never important. For this rock Williams^ proposed 

 the name " Cortlandite. " 



Professor B. K. Emerson^ has described a peridotite from 

 Belchertown, Hampshire County, Mass., which exhibits most of the 

 characters of William's rock and to which he has applied the same 

 name, and Williams^ has published an analysis of a somewhat 

 altered occurrence from Howard County, Md. The analyses of 

 these rocks place them in Class IV Dofemane, Order i Perpolic, 

 and Rang i Permirlic, of the quantitative system. 



The rock to be described below occurs near the village of Penobscot 

 in Hancock County, Maine, in the Bluehill Quadrangle. It forms 

 a single outcrop, hardly 30 feet in length and breadth, located about 

 ^ mile east of Pierce Pond. The ledge rises above its surroundings 

 in such a manner as to resemble a huge half-buried bowlder, but 

 the rock is undoubtedly in place and owes its prominence merely 

 to a superior resistance to glacial erosion. Post-glacial weathering 

 has been very considerable, and a red soil containing scattered 



1 G. H. Williams, "The Peridotites of the 'Cortland Series' on the Hudson 

 River near Peekskill, N. Y.," American Journal 0} Science, Third Series, Vol. XXXI 

 (1886), pp. 26-41. 



2 Ibid., p. 30. 



3 B. K. Emerson, Monograph XXIX, U. S. Geological Survey, 1898, pp. 346, 

 347- 



