20 TRANSACTIONS OF THE [oor. 19, 
almost nothing of a diagnostic character. Clay or kaolin, calcite, 
limonite, and indefinite dirt make up the slide. Very little recog- 
nizable epidote has been noted. 
An interesting and exceptional alteration is afforded by the dike 
at Palmer Hill, near Ausable Forks. The feldspar has yielded a 
colorless, negative, uniaxial, rather brightly polarizing mineral with 
abundant rectangular cleavages. This is scapolite. It often forms 
secondary nests with quartz. Scapolite as an alteration product 
from plagioclase has long been known in connection with various 
rocks which are associated with the apatite deposits of Norway, and 
has more recently been discovered in the same relations in Canada.' 
The process has been discussed by Judd.’ It is urged that solutions 
of sodium chloride penetrate the plagioclase along ‘solution 
planes,’” after which dynamic metamorphism in connection with the 
sodium chloride changes the plagioclase to scapolite. In the present 
instance there seems to have been no dynamic metamorphism, but 
it is likely that infiltrating sodium chloride or of hydrochloric acid 
may have aided the change. Lacroix has also recently described 
the alteration of plagioclase to dipyr, in a diabase of the Pyrenees.* 
The Palmer Hill dike yielded, on analysis, the results in column 
J. By its side is placed for comparison No. II, which is the 
analvsis of a diabase from near Boston, and No. III is one from 
the Keene Valley. 
I. Kemp. IT. Hobbs.5 III. Leeds.§ 
SiO, . . - : : . . 45.46 48.75 43.41 
Al,O, - 5 . ; c 19.94 UGloll 19.42 
Fe,0, : : - 0 . 15.36 0.41 5.72 
INNO) : ¢ 0 : : _ 13.62 6.69 
CaO . 3 : : - : ono 8.82 Ont 
MgO . c : . 5 : 5 Ae 3.37 5.98 
MnO . : : . ; 5 _ 0.91 — 
K,O ° ; 3.21 2.40 0.47 
Na,O 5 ; 2.12 1.63 4.39 
TiO, bri gir: Semin eS 0.99 0.35 
LEO 5 _ 0.68 — 
CO, : c _— trace 2.00 
Fes, : 5 : — trace _ 
Loss : . : 5 Zhai) -— 3.00 
99.66 100.17 100.54 
Sp. gr. : : ¢ : - 2.945 2.985 
1F. D. Adams and A. C. Lawson, On some Canadian Rocks containing 
Scapolite, etc., Canadian Record of Science, 1888, p. 185. The paper gives 
copious references to the literature and a valuable review of the same. 
2 J. W. Judd, on the Processes by which a Plagioclase Feldspar is converted 
into Scapolite, Mineralogical Magazine, vol. vili, p. 186. 
3 For the description of solution planes, see J. W. Judd, Q. J. G. 5. xli, 
383, 1885; xlii, p. 82, 1886; Mineralog. Mag. vii, p. 81, 1886. 
4 A. Lacroix, Sur les Phénomenes de Contact de la Syenite elaeolithique de 
Pouzac, Comptes Rendus, No. 110, p. 1011, 1890. 
5 W.H. Hobbs, On the Petrographical Characters of a Dike of Diabase in 
the Boston Basin, Bull. Mus. Comp. Zo6l., xvi, 1. 
6 A. R. Leeds, Notes on the Lithology of the Adirondacks, 30th Ann. Rep. 
N. Y. State Museum, p. 102. 
