1 84 The American Geologist. September, 1903. 
Two small sections of the hand specimens described were 
examined microscopically by Prof. R. W. Brock, who has 
kindly furnished me with the following account of them: 
"The rock is a hypidiomorphic granular one, consisting 
essentially of microperthite, microline and hydronephelite, 
nepheline, with some biotite, amphibole and a little diopside 
(?). A little magnetite and some calcite secondary after the 
pyroxene are also present. 
"The feldspars which make up the bulk of the rock are hy- 
pidiomorphic — some of them show crystal outlines. They have 
the well-marked cleavage and other characteristics of the alkali 
feldspars. No lime-soda feldspar was seen. 
"Hydronephelite; A clear white mineral in leafy or colum- 
nar aggregates filling the interstices between the feldspar crys- 
tals. Index of refraction is low, double refraction high. It 
possesses rude cleavage parallel to the long axis of the col- 
umns, and this is the direction of the axis of least elasticity ; 
uniaxial; positive; gelatinizes with acids. It is no doubt an 
alteration product from nepheline which originally filled the 
interstices between the feldspars. 
"The biotite is the most abundant colored constituent, but 
is present in only small amount in the sections. It occurs in 
two forms, in stout -thick plates, having a deep brown color 
scattered through the sections, and in small green scales, giv- 
ing generally a lath-shaped section showing perfect cleavage. 
These occur in groups, and do not appear to be altered forms 
of the brown biotite. 
"Amphibole; Several large crystals of a deeply colored blu- 
ish green amphibole, somewhat resembling arfvedsonite, occur 
in the section. They do not show crystal terminations. The 
pleochroism is strong: c — deep bluish green, b — olive green, 
a — deep yellowish green. c > b > a. The double refraction 
is low. The extinction is high, c : c=20°, which differenti- 
ates it from arfvedsonite. b=b, so that the clinopinacoid is 
the axial plane. It is optically negative — the axial angle ap- 
pears to be small. It sometimes holds inclusions of brown 
.biotite and is somewhat decomposed. It resembles arfvedsonite 
in some respects, but the latter has an extinction of c : 0=76°. 
Hastingsite bears a close resemblance but its extinction is 30°. * 
♦ Am Jr. Science, 1896, p. 210. 
