34 ANALYSES OF ROCKS AND MINERALS, 1880-1908. 
I. Biotite granite, Sykesville. Tehamose. Contains quartz, feldspar, and biotite, 
with accessory magnetite, zircon, and apatite. 
J. Inclusion in I, derived from limestone. Yellowish central portion. Consists 
of epidote and quartz, with a little chlorite. 
K. Same inclusion, fine-grained dark outer zone. Quartz, garnet, and epidote, 
with a little magnetite. Feldspar and muscovite in some portions. Descriptions 
by Keyes. Analyses by Hillebrand, record No. 1220, with the same limitations as in 
the Guilford, Woodstock, and Dorseys Run granites. 
L. Typical gneiss of Washington, D. C., from quarry. of Potomac Stone Company, 
1 mile below Chain Bridge. A ‘“‘basic” granite. 
M. Fine-grained, fissile chloritic gneiss, from northwest of Cabin John Bridge. 
Also a ‘‘basic” granite. P. R. C. 1753. 
N. Fine-grained, hard gneiss, from the second lock at the Great Falls of the Potomac. 
Alsbachose. Probably of sedimentary origin. 
Described by Williams. Analyses by Hillebrand, record No. 1459. 
4. MISCELLANEOUS ROCKS. 
A. Typical diabase, Rocky Ridge. Auvergnose. Analyzed for J. S. Diller, but 
not described. Analysis by E. A. Schneider, record No. 1370. 
B. Ottrelite-phyllite rock, Liberty, Frederick County. Analyzed for G. H. Wil- 
liams, but not described. P.R. C. 1754. 
C. Chloritoid separated from B. Analyses B and C by L. G. Eakins, record No. 1349. 
D. Quartz schist, Shoemaker quarry, near Stevenson Station, Green Spring Valley. 
Described by Bayley in Bull. 150, p. 302. Contains quartz, muscovite, occasional 
tourmalines, microcline, zircon, and iron stains. Analysis by Schneider, No. 1370. 
P.R. C. 119. 
E. Mica separated from D. Analysis by Schneider, No. 1377, 
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