386 The American Naturalist. s [April, 
consisting of a film of minute needles. It may be referred to the 
variety of Göthite known as ‘‘sammet blende,” and is strikingly 
beautiful when its color and texture appears in a direct light. The 
limonite is shown in siliceous concretions, sometimes in concentric 
shells, and in other instances enclosing ferruginous pebbles, between 
which an infiltrating seam of iron cement has thrown interior parti- 
tions. The quartz groups are large and handsome, and occur as 
geodes or small rounded mounds of slightly divergent, faintly amethy- 
stine crystals. They are characteristically alike in having the individ- 
uals composed of groups of interfering pyramids, amidst which the 
central crystal, most fully developed, rises, and at a distance seems to 
blend the jutting faces of the subordinate rhombohedrons with its own, 
and form a single stout termination. This peculiarity gives a slightly 
drusy appearance to the entire surface. The elements of as many as 
twenty-four pyramids are seen in some of the groups. These quartz 
groups have all doubtless formed the central crystallizations of geode- 
like siliceous balls or conduits. They have been found by Mr. Smith 
at the lower levels of the surface diggings, near the underlying serpen- 
tine ledges. The ores in which they occur are highly siliceous limon- 
ites, which were deposited, in all probability, by the oxidation of iron 
salts carried upward by thermal waters flowing through the crevices of 
the serpentine mass, and fed to some extent. by surface waters carrying 
dissolved iron oxides, a process made familiar by the papers of Drs. 
Hunt and Julien. This view is supported also by Dr. Britton (Geol. 
Richmond Co. Ann., N. Y. Acad. Sci., Vol. II., p. 177) 
Now the experiments of Schafhautl, Senarmont, and Daubrée, in 
making artificial quartz, have shown that gelatinous silica and glassy 
silicates are attacked and dissolved by highly heated waters, either 
alone or assisted by hydrochloric or carbonic acid, and that such 
solutions deposit hexagonal pyramids of quartz. These interesting 
quartz groups in the iron beds point conclusively to the exudation, 
from the serpentine rocks below, of warm springs, at whose mouths, 
upon cooling and removal of pressure, the quartz pyramids have been 
formed. Their amethystine hue is attributable to manganese, which is 
a prevailing ingredient of the iron ore of this region. 
to the source of the silica, it is a possible hypothesis that it has 
been supplied in a soluble form from the slow change involved in the 
decomposition of hornblende masses, and the formation of serpentine. 
In such a change there would certainly be a discharge of silica or sili- 
cates, and they would naturally enter into solution in subterranean 
