Vermont phÅ“nix. [volume] (Brattleboro, Vt.) 1834-1955, 1880-11-19
MATTER.
OF the Composition Of tho Rocks.
No. o.

This subject opens so broad field that it
will be impossible to travel over it in the
brief space of a newspaper article hence it
must suffice to examine few only of the
hundreds of minerals, their chemical consti-
tuition and the rocks resulting from their
union.
In the FIRST place IL may be observed that
the rocks are not only divided and subdivid-
ed geologioally as shown in No. 8 they are
also divided into two distinct classes without
reference TO the geological divisions, and
might not improperly be called simple and
complex but they are more generally known
by the terms, minerals" and aggregate
rocks" mineral bears the same relation 10
an aggregate rock that an element does to a
compound chemical substance. Oxygen and
hydrogen gases are the elements united in the
compound substance, water. That valuable
aggregate rock, granite, is composed Of the
minerals, quartz, feldspar and mica. The
clements Of water never vary in relative
quantity but the minerals that enter into
the composition Of granite change their rela-
tive proportion, and hence the appearance Of
the rock to such an extent as TO merge it in
to a rock bearing another name, and some
times making it difficult to decide where the
line Of demarkation should be placed. Thus
granite becomes gneiss by containing less
feldspar with the quartz more distinctly
granular and through this variation of one
mineral in quantity, and Of another in the
degree of communion, these rocks insensi-
bly, glide into each other. Sometimes ar
raDgement produces an important effect in
appearance, as in graphic granite, in which
the quartz and feldspar are not very finely
pulverized, and 30 arranged as TO resemble
Arabic or Hebrew letters. Syenite, another
of the plutonic rocks, differs from granite on
ly in containing hornblende instead of mica.
One of the most common minerals, known
by everybody by its light color, hardness and
translucenoy. is quartz. Many varieties are
known to the mineralogist, as terruginous
fetid, milky, stalactical and others, but only
n general description can be given. When
pure, it is composed, according to Thompson
of one equivalent Of silicon and one Of oxy-
gen but Berzelius gives three equivalents Of
oxygen. According to the latest and best au-
thority, its composition is, silicon-some-
times called silicium-46.67, and oxygen 3d.
33 in 100 parts In the progress Of scientific
knowledge and the Substitution of new terms,
this mineral is not now generally known by
the old terms, quartz" and "sile1," but by
the modern expressive names, "slica," or
"silicic acid" It is really the oxide of sill
con.
Common feldspar bears some resemblance
| tn II 10 cOnnatimaa rnlOrluec oFfan
reddish or flesh -coored, softer than quartz,
and may be scratched with any steel instru-
ment or this mineral there are several va
rieties. The common variety is composed of
silica, Go. 81 alumina, 1913; potash 1886
in 100 parts. Albite is nearly Identical the
| principal difference being in containing soda
instead of potash, Feldspar mixed with
small quantities Of other minerals forms en-
tire mountains in Siberia and in the north
and west of Scotland
Mica, one of the most widely distributed
minerals occurs white, green, brown, black
and in other shades, flexible and elastic, and
is easily divided into thin lamine. It's tenac-
ity gives transparent specimens a superiority
over glass when coming in contact with heat
1t is said that large plates of it are found in
Russia yard in extent. The composition
of mica varies in different varieties. The 81.
berian is composed of silica, 4s; Alumina,
1925 potash s.7j oxide of iron, 4.5 man
ganese, 0.5; water l.25.
Carbonate of lime Common limestone
marble, chalk) is, as its name implies, a sail
composed of carbonic acid and lime, united
in different proportions in different varieties
The common variety is impure and contains a
small por cent. of silica, alumins and oxide
of iron. When the carbonic acid is driver
of by heat in kilns, lime remains, sometimes
called quick lime" but it is still compound
body. Farther analysis shows that lime il
composed of calcium and oxygen. Hence
the chemical name Of lime is oxide of cal
cium.
Sulphate of lime (plaster of Paris, gypsum
is an abundant mineral found in many place.
in the United States and in Europe. 1t re
ceived its commercial name from having
been first exported from Paris, As its nam'
implies, this salt is compound of sulphuri'
acid and lime. Some chemists give it l pc
cent. of muriate of soda while others omit it
1t will be seen that the difference betweeI
the sulphate and the carbonate of lime arise
from the acidifying principle-the forme
containing sulphuric, and the latter carboni
acid. Sulphurc acid being a compound o
sulphur and oxygen, sulphate of lime is
compound body consisting of sulphur, oxygeI
and calcium.
Hornblende is a dark colored mineral
Opaque, sometimes black, shining, tough
some specimens pseudo metallic. 1t oftel
enters into granite and gneiss, aud is presen
in greensboro and syenite. Here again diff
ferent varieties possess different compost
ton. According to Bonsdorf the deep greer
is composed of silica, 472l alumina, 1894
lime, l2. 73; magnesia, 2l.s6i oxide of iron
22S; oxide of manganese, 057; fiuoric acid
O9O water, 044
1t may be remarked in conclusion, that a
of the 10 or - inorganic constituents of soil
and of plants, the most Of which are men
toned above, were once imprisoned in tn
rocks but by slow, erasive, atmospheric AM
aqueous agencies they have been released
and rendered available by dissolving rains
making it possible for the husbandman to til
the earth with certainty Of reward, at tn
same time that he is laying up treasures o
knowledge granted only to those that ar
, proved worthy by study andrehection.
, Wilmington, vt. 3. Z. O.
A D,,rv NovvI AnyFNTrRF IN A NEW STYLE