434 F. Prime, Jr.—Limonite Deposits of the Great Valley. 
from which the ore is extracted by means of picks or shovels, 
powder never being employed. 
he ore does not occur casually at any point in the lime- 
stone, but forms regular lines, following apparently the out- 
crops of certain beds. In Lehigh County, Penn., where I have 
been engaged on the geological survey of the State during the 
past season, there are three or four of these lines. During the 
progress of the survey I was much struck by the fact that the 
two most important and promising lines of outcrop were—one, 
at the base of the crystalline schists (forming the South or 
Lehigh Mountain), and overlying the Potsdam sandstone con- 
formably; the other, near the line of junction of the Calciferous 
limestone with the Hudson River slates. The mines along 
these two lines—following the topography of the country— 
were in place, richer and more permanent than those of the 
belts between, which had been more decomposed in situ and 
were generally leaner. 
peculiarity of these two lines of outcrop, and one to which 
I particularly desire to draw attention, is the occurrence of 
what I at first mistook for a highly altered slaty limestone, but 
which on subsequent analysis proved to consist in great part 
of damourite (hydrated potash-mica). The following are analy- 
ses of this damourite-slate : 
I. From Fogelsville, Lehigh County, within a few hundred 
feet of the contact of limestone and slate, by Dr. F. A. Genth. 
. From Hensingerville, Lehigh County, within 300 feet of 
gneiss, by Mr. Sydney Castle of the University of Pennsylvania. 
From Allentown, Lehigh County, within 150 feet of 
contact of the limestone with Potsdam sandstone: by Mr. 
Pedro G. Salom of University of Pennsylvania. 
IV. From another quarry close to III; also by Mr. Salom. 
L ia Ii. IV 
SiO, 49°92 45°40 59°30 39°80 
Co, Clas Ree Aarne 14.40 
Fe,0O, 0-91 506 2 2-40 
Al,O, 34°06 24°69 } 30:80 23-95 
tiga papi trace 
M. a i 4 13°56 trace 1°94 
CaO O11 trace truce 9°85 
Na,O 0°74 0:27 151 0°52 
K,0 6°94 5°85 6°24 3°34 
H,O 6°52 4°80 4°70 6°00 
sentra ie rice 
100°97 99°63 102°05 102°20 
As typical damourite contains 11-77 p. ¢. of potash, it is evi- 
dent from the above analyses that I. contains 55-40 p.c. of 
ourite; II, 49-70 p. c. ; III, 58:02 p. c.; and IV, 28°30 p.c. 
