VrRGTNIA. 115 
The results of Professor M err i man's recent tests <>f slate from the Williams and 
Pitt quarries are given on page 123. 
Bremo. — Slate has been prospected on the estate of the late Dr. Casey Charles 
Cocke, 2 miles west-northwest of Bremo Bluff, in Fluvanna County. 1 1 occurs in the 
ravine east of the house and also on the hill northeast of it. The strike is X. 18°-23° 
E., dip nearly 90°. A little northwest of the house is a dike of olivine basall 5 t<> It) 
feet wide. The following results are from an examination of specimens obtained 
within a few feet of the surface which, therefore, belong to the "top." 
This slate is dark gray, but its lightness of shade is in part the result of weather- 
ing. It will prove to be darker below the zone of weathering. To the unaided eye 
it has a fine texture with a somewhat tine and very lustrous cleavage surface more 
or less dotted with minute lenses or crystals. It is slightly graphitic, but not mag- 
netitic, shows pyrite on sawn edges, does not effervesce in cold dilute hydrochloric 
acid, has an argillaceous odor, is sonorous and very fissile. The slate from one of 
the openings has exceedingly minute veins of muscovite. 
Under the microscope the Bremo slate shows a matrix of muscovite (sericite), 
with a brilliant aggregate polarization. 
There are abundant quartz grains up to 0.09 by 0.03 and 0.13 mm. long, the larger 
ones surrounded by secondary quartz radiating along the cleavage; about 50 lenses 
and crystals of pyrite per square millimeter, measuring up to 0.09 by 0.02 (excep- 
tionally the lenses are 1.5 mm. long) , with their longer axes in the cleavage. There 
are also square and rhombic spaces lined with secondary quartz, measuring up to 
3.6 mm., left by the dissolution of cubes or distorted cubes of pyrite. In some speci- 
mens there are 65 such cavities to the square inch, in others none. There are lenses 
up to 0.56 by 0.11 mm., consisting of quartz and muscovite or of these and chlorite 
ind pyrite, or of chlorite and muscovite, the folia of muscovite and chlorite lying 
icross the cleavage; also muscovite scales up to 0.09 by 0.02 mm. Throughout the 
natrix much dark-gray material occurs in exceedingly fine dots (graphite?). There 
ire also some dots of hematite. Rutile needles are not very plentiful up to 0.01 mm. 
ong; also a number of very irregular particles of rutile up to 0.05 mm., consisting of 
i network of crystals ( " sagenite twinning" ) forming angles of 120° and 60°. A few 
ragments of zircon, an occasional crystal of dark tourmaline up to 0.05 by 0.02 mm. 
•are flakes of biotite, no carbonate. 
The chief constituents of Bremo slate, arranged in descending order of abundance, 
ippear to be muscovite, quartz, pyrite, kaolin, chlorite, graphite (or carbonaceous 
naterial), rutile, with accessory tourmaline, zircon, biotite, and hematite. 
This slate differs from the Arvonia slate in its finer texture, probable slightly 
ighter shade, and slightly higher percentage of pyrite. It has less biotite and, at 
east in the " top," no carbonate. 
Core drilling or excavation deep enough to penetrate the "top" is amply war- 
anted by the above determinations. a 
Snowden, Amherst County. — The Snowden slate deposit is on the southeast side of 
he axis of the Blue Ridge, north of the cut through which the James River flows. 
t is situated about 18 miles north-northwest of Lynchburg. (See map, fig. 13. ) The 
late crops out in a longitudinal valley with Rocky Row Mountain mi its northwest 
ide and a spur of Big Piney Mountain on its southeast side. It strikes N. 65° E. 
nd has quartzite southeast of it. The general structure and the areal relations of 
tie slate have not yet been exhaustively investigated. h 
The only quarry in operation in 1904 was that known as the Williams Brothers 
late quarry, on the property of the Virginia Slate Mining Company, which lies:; 
■Usiate outcrops on this property were referred to by J. L. Campbell, Tenth Census, special report on 
wilding- stones, vol. 10, 18X4, p. 181. 
■ &See Campbell, Bibliography, p. 143, also Geology of the Blue Ridge, near Balcony Falls, \ a.: Am. 
<pur. Sci., 3d ser., vol. 28, 1884, pp. 221-223. 
