The record-union., 1895-07-20
ROCK FOR THE PUBLIC HIGHWAYS.
Plenty of 1t Available at the Folsom
Prison.
1Iineralog1cal Survey Shows It to be
Fine Grained, Tough, Hard and
Eminently Fit.


vicinity of Folsom State Prison and the
site of the proposed macadam quarry to
be opened for the purpose of obtaining
rock to be placed on the public highways
of the State. He has furnished his re-
port to the Bureau of Highways, and it is
very interesting reading to those who are
anxious for the improvement OF the roads
OF the State.
The report says that the proposed
Quarry is situated in the Immediate vi
cinity of the State Prison. on the south
side of the American River. The cutting
OF the canal of the Folsom Water Power
Company has resulted in making con-
tinuous exposure of rock in place. eX-
tending from the dam of the Power Com
pany, half mile above the prison, to the
Town OF Folsom, a mile and a quarter be-
low 1t. An examination was made along
this canal for distance of !. 800 feet for
the purpose OF ascertaining the character
OF the rcck exposed, and from samples
collected to determine it's adaptability to
lis use on roadwayS. The investigation
was also extended to the north side of the
river and also 10 the slopes and hilltops
lying east of the canal, with view to
getting some knowledge of the geological
structure OF the vicinity.
GEOLOGY.
The examination thus made shows the
geology of the area In question to be quite
simple, there being no complex geOlogi-
cal features. From point few feet
south OF the power-house, in front of the
prison, along the canal nOrthWard TO the
dam of The Folsom Water Power Com
pany,a a distance OF nearly half a mile
the rock IS grano-diorite. At point di-
rectly opposite TO the main entrance to
the prison the grano-diorlte gives place
TO a dark-colOred amphibOle rock, ap-
parentIy an altered diorite.
An examination OF the rocks in the bed
of the American River opposite the
prison shows the contact to be lily de-
fined. The granite is the later rock, and
has crushed and broken The amphibo
rock into fragments and included them
IN tie magma forming Drecciated zone,
200 feet or more in width. Small granite
veins occur, and little veinlets and
punches of feldspathic material are found
10 be segregated here and there from the
granite masses.
beyond the brecciated zone the amphi-
bole rock is quite uniform in appearance
and Is found to consist largely of horn
blend, with some feldspar and OCCASION
ally quartz. The rocks were examined
carefully from the granite contact south
ward on the east side OF the American
side south ward from the contact for
distance OF 100 feet. For distance of
Z,UUOle southerly Y from the contact along
the bank Of the canal the amphibole rock
ls found TO be massive and in place, not
more than 10 per cent. OF IL being too
much crushed and altered to render un-
suitable tor use on roads.
Beyond what is known as the "visitors'
road" small ravlne 1000 feet south of
the prison, III the direction of Folsom,
the rock, with few exceptions, is found
slaty and crushed, and with a lew excep-
lions may not be depended on to furnish
any considerable quantity of good rock.
THE GRANO-DIORITE.
The rock Quarried SO extensively at
Folsom for building purposes, in the
classification of rocks, comes under the
nead Of what has been very appropriately
named grano-diOrite, that is, rock in
which prominent mineral constituents
partake of the nature of both granite and
dioriie.
True granite is rock composed of
othoclase potash feldspar), quartz and
either black mica tblotite or white mica
lmuscovite). or both, together with some
accessory minerals. principally apatite
calcium phosphate) and iron ores
Dlorite is composed Of a plagioclase
tlilne. soda, feldspar, usually oligocIase)
and hornblend, and may or may not con-
laln ellher quartz or mica.
1he olson granite Is q com bination of
these two distinct rock species; in fact,
true granite Is uncommon in California
his granite contains both orthOclase and
plagioclase, and both hornbleud and
black mica in about equal proportions,
while quartz, though present, is really
subordinate to the feldspar, consequently
the name granO-diorite is well suited to
Its peculiarities.
THE AMPHIBOLE ROCK.
Pending microscopic examination of
the rocks constituting the amphibole
area, tue nlneralOgiSt inclines 10 the be-
lief that they are diorite in various stages
OF alteration. In texture these rocks
range from rather coarse granular to
aphanitic kinds, the main mass being
line grained, tough and hard. The rock
appears to be eminently suited to use on
roadways. and when properly sized and
laid on road bed. should make smooth
and durable highway.
SLATY AND SCHISTosE ROCKS.
Half a mile south from the power
house, in southerly direction. the rocks.
While evidently very similar to the am
phlbole rocks just described, have been
subjected to much crushing and move
ment, and the process OF alteration and
decay has progressed 10 sucn an extent
as To render them unsuitable for mac
u
hrm, massive rock is required.
QUANTITY AVAILABLE.
AS has been previously stated, the zone
of amphiDOle rocks suited for macadam
is about :. 600 feet broad and is known to
extend III northwesterly direction a
distance OF $500 feet. with every proba-
blilty OF a much greater extent, which
could not be determined without a num-
ber OF pits being dug. on account of its
being covered with soil.
Along the line of the canal the stones
rise at an angle of from 250 TO So, the
hills being about 150 feet hi1 her than the
canal al a distance OF 500 feet from it. At
q greater distance they are somewhat
higher. The abrupt slopes will, gener-
slly speaking, need but little stripping.
but on the more gentle inclines aud hili-
tops, and in the small ravines il will be
found necessary to strip ten feet or more
before firm rock Is encountered in con-
siderable quantity.
The site Is well located and the quantity
OF material obtainable is very large, in
deed, If surface indications can be relied
upon. The capacity of the quarry will
oe determined by the manner and extent
ol operating. The question of quantity
eeeils 10 be matter OF secondary cousid-
etaIlon. The exposure thus far made in
uIc1tes That the waste unsuited to use as
Hacaaain, due to all causes including
stilppihs o! the surface soil, will not
eAceeu - per cent. of the entire amount
ouarfied.
D"YBR AND SMITH
Two men Nho Are Alleged TO Have