Staunton spectator. [volume] (Staunton, Va.) 1849-1896, 1853-04-20
Geological Cabinet:
= ,an Introduction and .Aid to Reading.
BIZ JOSIAH HoLBReoK.
Continued

Nos. 8. and I. Granite is composed
quartz, felspar, and mica the.latter throw
about in every possible direction; render
ing the rock unsiratitpd, not slaty. 1t dlf
fers widely in the degree offneness of tn
three ingredients composing it, the mlc'
sometimes being in plates two feet or more
in diameter at other times, in fine span
gle like scales, thickly scattered through
the rock. The quartz or felspar, also, vary
greatly in the size of the masses composing
the granite.
Fine granite is best fitted for purpose:
of architecture for which it is extensively
used in many countries. In the United
States are many quarrles, furnishing build.
ing materials for all our seaports and many
inland towns and villages.
No. 8. Gnelss is slatY, granite, rendered
SO by the uniform direction of the mica
1t hence splits in slabs of large and smooth
surface, fitting it for sidewalks, floors,
bridges, and, many other purposes Of econ
omy and convenience. 1t is the prevail
ing rock on New York island as it is in
many parts of New England, and many
other parts of the world. The color of .gneiss
depends, of course, upon, that Of the ma
terials composing it, especially the mica,
which is sometimes black, giving black
or dark color 10 the gneiss. 1t is moro
commonly Of a lightish grey, and some
times silvery. e.'.. ", T..
No. 9. Mica Slate resembles gneiss,. but
is composed of quartz and mica. Eelspar,
composing part of granite and gneiss, Is
wanting in this rock. 1t frequently has an
undulating surface, but is smooth. 1t splits
readily, andIi used for purposes similar to
those of gneiss. Garnets are more abun-
dant in this than any other rock; and this
rock contains more Of those than any other
crystals. y g., .,i.,; i.rr'., -erv-,:
No. 10. Hornblend is black, greeni' or
other dark colors. 1t is more tough than
hard, and is an element of rocks much us
ed in architecture, also forming some of
the most beautiful scenery in the world.
No II. Sienite is commonly called gran
te, but differs from it in taking hornblend
in place of mica. The Bunker Hill Monu-
ment, (Mass.) Merchants Exchange, As
tor House, Rutgers Institute, and numer-
Gus other buildings in, New York, and other
cities, are built OF siente, commonly called
Quincy granite. Cleopatras Needle, E.
gypt. is sienite.'.
No. 12. Basalt!,,. The Giants Causewa ay
is composed of basaltic pillars, many of
which are six-sided prisms from six inches
to foot or two in diameter; IN blocks a.
bout the same length. with one end round
ed and the other followed, SO as exactly to
match and are piled upon each. other to
the heighth of 200 feet or more. Rocks
nearly resembling these, and piled upon
each other in similar manner, form the
palisades on the Hudson, the two bluffs at
New Haven, Mount Holyhoke, and many
other mountain masses in this and other
countries. The same kind OF rock is scat
tered over many countries, in the form Of
boulders, and is frequently known by the
name of iron stone. 1t is composed prin-
cipally of hornblend or augite, WHICH 1t re-
sembles, and felspar with large portion of
IRON. Basalt, greensboro, and other rocks
of the same family are much used for build
ing.
Nos. 13 and IA. Lime formations are
extensive, various, useful, and sometimes
beautiful. They embrace common lime
stone. nearly all marbles, chalk, and many
beautiful crystals. The older formations
are in coarse grains, which give 1.-THE name
of granular lime. The more recent is fire.
quently finer Or more compact, when it is
called compact lime. 1t is frequently found
in rhombic crystals, when it is called
rhomb spar. When these crystals are trans
parent, they are called Iceland spar, and
produce double refraction, giving one line
or letter seen through it the appearance ol
two.
All these formations are the carbonate OF
lime, composed Of lime and carbohic acid
When burnt, the acid is thrown from the
lime, when ii is reduced to quick lI,ne,- and
fitted for various. uses ia building; also fol
manuring land;for which it is extensively
used. White limestone and milk quartz
are sometimes confounded, but they may
be, easily. distinguished blythe knife, as the
former can be cut, and the latter not, and
more certainly by an acid, as the former
ef1ervesces, and the latter not.
No. Is. Gypsum is the, sulphate Of line
and of course composed of sulphuric acid
(oil of yitaoD and lime. in Italy and other
countries it appe ars in the form of alabas.
ter, which receives atfine polish, and is
translucent. When crystallzed in trans.
parent plates, itis called selenite, (moon
stone.) At sometimes appears in fine silky
fibres, when it is called fbrous GYPSUM
Radiated gypsum is another beautiful va.
rIety ofthis mineral. 4
Gypsum is powerful manure, and is
much used for ornamental work, in plas.
tering rooms also for busts and casts o
various kinds. nos ..>.e"..,
No. 16. .Serpenthe rocks form extensive
barren ridges, but contain chrome ore,
magnesia, asbestus, and other useful anc
curious deposites. It takes its name from
its variety of cclcrslikeAtie serpent, though
its prevailing color is green. The prevail.
ing rock at Hoboken and Staten Island is
serpentine; which extends, with frequent
Interruptions, through New Jerseys Penn,
sylvania, and Maryland, into Virginia. II
abounds in various parts Of the world.
No. II. Tale, like serpentine, contains
magnesa. 1t is sometimes known by the
name of French chalk. 1t has a greasy
feel, and is easily cut with knife OF
scratched by the finger nail.
No. IS. Soapstone is composed of tale
minutely combined with quartz. 1t is cas-.
lily cut with an axe or saw, turned in q
lathe, smoothed with plane, and thu:
changed into any form desired for economy
or convenience. 1t is less abundant thar
serpentine, but is frequently found with it
No: 19, Sandstone IS composed of grain:
Of sand or quartz cemented into rocks