BARE MOUNTAIN, IGNEOUS ROCKS. 155 
original shale of the series, now a silvery or greenish-gray mica schist, 
is well exposed near Gold Center. The schist is a fine-grained, 
foliated, and locally crenulated rock composed of micaceous minerals 
with some quartz and feldspar. Small magnetite and pyrite crystals 
are common in certain bands and are evidently contemporaneous with 
the other metamorphic constituents. The planes of schistosity are 
usually parallel to the bedding planes, which are in places ripple 
marked, although in certain instances the foliated structure crosses 
the original bedding at right angles. Weathered outcrops have a 
typical rusty appearance. A single thin section under the microscope 
showed a thoroughly recrystallized rock lacking all traces of original 
structure. The rather well oriented micaceous minerals are musco- 
vite, biotite, and limonite-stained chlorite, and grains of quartz and 
orthoclase lie between their blades. Tiny magnetite crystals and 
grains are abundant. 
The lower limestone member of the series was deposited in a sea 
of medium depth, into which for a long period little or no fragmental 
material was carried. The upper portion of the series, on the other 
hand, was deposited in a shallow sea which at times received frag- 
mental material of varying grain. The quartzites and schists mark 
periods in which the deposition of fragmental material exceeded 
organic and chemical sedimentation, while the interbedded limestones 
indicate a reversal of the dominant process. A few poorly preserved 
fossils (one of which is identified by Mr. E. O. Ulrich as a gasteropod 
suggesting E ccyliopterus or some other euomphaloid genus) were 
obtained from Bare Mountain, and although by no means diagnostic 
of the age of the series, they are probably younger than the Cambrian 
and older than the Carboniferous. The basal quartzite may be an 
intercalated bed in the Pogonip limestone or possibly may represent 
the Hamburg shale of the Eureka section. The thick limestone on 
lithologic grounds is correlated with the Pogonip (Ordovician) lime- 
stone, while the overlying quartzite is probably the Eureka (Ordo- 
vician) quartzite of Hague. This upper quartzite and schist rather 
closely resemble the Eureka quartzite of the Kawich Range. The 
area covered by the two formations is roughly indicated on the map 
(PL I), but future work will prove the distribution much more 
complex. 
IGNEOUS ROCKS. 
Post-Jurassic pegmatites. — Pegmatitic dikes from 2 inches to 4 
feet thick are common in the northern part of the range. The most 
widely distributed type is composed of white or very light pink feld- 
spar, with some colorless quartz and muscovite. None of the indi- 
viduals exceed a diameter of one-half inch. A less common variety 
° Hague. Arnold, Mon. U. S. GeoL Survey, vol. 20, 1892, pp. 54-57. 
