Deseret evening news. [volume] (Great Salt Lake City [Utah]) 1867-1920, 1908-06-09
Brief Notes on Its Physical Fea-
lures, Resources, and Development.
I. THE REIGN OF FIRE.

I which We're once supposed to be among
| the oldest rocks and to represent the
| primeyal cooling of the melted earth,
have really been thrust up from the
| oarth's interior subsequently to the
| formation of the cambrian and even OF
| the oarboniferous series. Granite rock,
of which the Salt Lalos Temple is built
is we'll known here, 1t seems certain
that 1t was once in n melted condition
and that IL cooled slowly enough to per-
nit its minerals TO form into distinct
crystals Its three main constituents,
as perceived by the naked eye are ~
hard, fAnty portions, called quartz;
~ horn-lile nuggets of grey,
yellow, OF sometimes pink color
called feldspar; go glittering scales of
white or darls-colored mica. The field
spar is rapidly changed by the at
inosphere into clay; the mica contains
iron, and is soon decayed or trusted"
by the oxygen of the air; while the
quartz grains fall apart 10 form ordi
nary sand. Such large rock crystals
as compose granite are characteristic
also of great class of these once
melted (f1re-forIned igneous) rocks
called the granitoid series. They arose
In molten condition from the depths
of the earth, assumed to be still so
highly heated that it's materials would
melt If relieved OF the enormous press
ure due to the weight OF the rocks
above them. Other kinds of igneous
rock abundant In Utah, contain much
the same Substances as granite, but in
still larger crystals. and are then
termed porphyifuc rocks.
THE FTISITIC ROCKS.
Still other kinds of fire-rormed rocks
abound in Utah, Some of these are so
fine-g grained that distinct minerals are
not to be seen In them. This Is the
condition of the once melted rock that
forms tho Henry mountains. 1t is
called trachyte, and has much the Same
composition as granite but without
crystals. Indeed, all rock that appears
to have been melted, such as basalt
volcanic CLASSY rock tobsidian), and
the various kinds of lava, are composed
of ubout the same elements as granite.
but differently combined or aggregated.
Though similar in composition, the fine
grained or felsitic series OF igneous
rocks are often very different from
granite In color, weight and texture.
The interesting and euphonious names
tI'achyte, rhyolite, syenite, phonolite,
and dacite are given TO tho less familiar
members Of this series; while basalt
and obsiuiaIl, the latter a well known
shiny, CLASSY. volcanic rock, constitute
the other main divisions of the igneous
group. Felsitic rocks abound In
parts of this state. In the case of the
Henry mountains, Garfield county the
rock basis consisting of trachyte, tells
plainly its own history In bygone
age, tho melted materials must have
welled up and become solid under tho
sedimentary rocks. for they have arch
ed these everything strata into large
domes The top rocks were gradually
worn away by tho weather. and tho
trslchyte masses are noweXposed Lava
Hf4.rr
of southeastern Utah, and many OF the
plateaus of that region are capped with
volcanic rock.
MODES OF OCCURRENCE.
Perhaps It should be remarked fur
Their that igneous rocks occur In dilles,
which have penetrated other rocks and
have solidiiied in them AS elongated
and narrow bodies OF various sizes: in
sheets, or surface flows that may later
be bufied---deposits of great lateral OK
tent compared with their thiclSness; in
laccoliths, or imprisoned Vows OF len
tioular shape; In recka, or roughly
cylindrical misses, such as might sol
idify In the conduit Of volcano. in
bosses, or Irregular, projecting, rounded
forms; and in vast irregular bodies
for which no single term ia used. The
enormous masses Of crystalline rocks
like granite that occasionally occur
here and that in some countries cover
hundreds Of square miles appear to
have fused their way upward by melt
ing tho rocks lying over them. These
formations are called batholiths. The
different methods OF occurrence have
an important hearing on the texture
OF the rochA.
THE CONMONIEsT ROCK.
quartz, or flint rock. the most nbund-
ant, not only OF the once melted ma
tsrials but OF any OF the rocks what
soeyeri may be picked up almost every
where, Though generally considered Of
ignoous origin. II is sometimes deposited
from water, being somewhat soluble In
hot alkaline solutions. In this form II
occurs chiefly around certain hot
springs and geysers, or ia the form
OF petrihod trees, Hardness Is its fea-
ture, only the topaz. the co1indum,
and tho diamond ranking above II In
the scale OF hardness. II assumes many
forms. most Of which OCCUR In Utah.
Mention OF the chief kinds VI this well
known material may be OF interest 10
Inexperienced observers
Mineralogists divide quartz rocks inbo
three classes; the vitreous varieties,
distinguished by their CLASSY fracture;
| the chalcedonic varieties, having sub
| vtroous or waxy lusbnr, and Henerally
! translucent; and the Jaspery Varieties.