70 SLATE DEPOSITS AND INDUSTRY OF UNITED STATES. 
These scales and lenses number from 10 to 14 per square millimeter, of which aboul 
half are chlorite. Multitudinous minute dots of bright red hematite occur through] 
out the slate, to which and the chlorite it owes its purplish color. Among thesi 
dots are many particles of pyrite, some of which measure up to 0.038 mm. A few oi 
these have passed into limonite. Slate needles (Ti0 2 ) are somewhat plentiful. Nc 
carbonate. Tourmaline 0.076 by 0.009 mm. The important constituents of this 
slate, arranged in order of abundance, appear to be muscovite, chlorite, quartz, 
talc, hematite, pyrite. 
Its deficient sonorousness is not due to the absence of a micaceous matrix, but tc 
the presence of a large amount of chlorite and to about 5 per cent of talc. It is 2 
mica slate. 
Mount Ephraim. — About 4 miles southwest of the Bennett Creek quarries and one- 
fourth mile south-southeast of the village of Mount Ephraim, in Montgomer) 
County, east of road to Barnesville and north of Little Monocacy River, on th( 
property of Abraham Harris, a similar slate has been prospected. The cleavage 
strikes N. 30°-35° E. and dips 70° E. The bedding probably strikes N. 30° E., dir 
uncertain. 
The characteristics of Maryland slates are shown in the table facing page 124. 
MINNESOTA. 
Location of deposits. — Deposits of roofing slate occur in northern Minnesota, a fev 
miles west of Duluth. At present, however, all the quarries formerly opened hern 
are abandoned, and the quality of the slate, as seen in specimens on the old dumps 
is hardly such as to justify reopening. 
References on Minnesota slates. — The following reports and papers, while notecc- 
nomic in intention, contain data of interest on the distribution and character of tht\ 
Minnesota slates: 
Hall, C. W. Keewatin area of eastern and central Minnesota. Bulletin Geol. Soc« 
America, vol. 12, pp. 345-376. 1901. 
Spurr, J. E. The stratigraphic position of the Thomson slates. American Journal c 
Science, 3d series, vol. 48, pp. 159-166. 1894. 
Winchell, N. H. The geology of Carlton County : Vol. 4, Final Reports Minneaot 
Geol. Survey, pp. 1-24. 1899. 
The geology of the southern portion of St. Louis County: Ibid., pp. 212-22] 
The geology of the Carlton plate: Ibid., pp. 550-565. 
The geology of the Duluth plate: Ibid., pp. 566-580. 
NEW JERSEY. 
The Bangor-Slatington slate belt of Pennsylvania is prolonged eastward into Ne 
Jersey, and roofing-slate quarries have been opened at several points, notably nes 
Newton and Lafayette. 
NEW YORK." 
By T. Nelson Dale. 
GEOLOGICAL RELATIONS. 
The slates of Washington County, N. Y., are a continuation of those of Rutlan I 
County, Vt, The Lower Cambrian affords greenish and purplish slates, like thos 
in Vermont described on page 104, which were once extensively quarried at Midd : 
a The slate of Washington County, N. Y., was described by the writer in part 3 of Nineteen 
Ann. Kept. U. S. Geol. Survey in 1899, but the matter appears liere in revised form. 
