-
PARAGENESIS OF THE MINERAL ASSEMBLAGE ATCRESTMORE, RIVERSIDE
COUNTY, CALIFORNIA
JonN W. Dalv, CaliJornia Institute oJ Technology,Posadena,
California.
INTRODUCTION
For more than twenty years the Creslmore locality has excitedthe
interest of mineralogists. This interest was first aroused
whenspecimens of blue calcite with monticellite and xanthophyllite
weresent to A. S. Eakle. The first publication appeared in 19141
andsince then numerous papers have been published on the
miner-alogy of Crestmore by A. S. Eakle, W. F. Foshag, A. F.
Rogers,and others.
Crestmore is situated on the extreme eastern lobe of the
JurupaMountains about three miles west of Riverside, California.
The
Jurupa Mountains are an east-west range roughty eight miles
longand three miles wide which parallels the front of the San
GabrielMountains.
The cement plant, l imestone quarries, and mine of the
River-side Cement Company are located at Crestmore. Quarrying
opera-tions were started some seventeen years ago. The rocks were
atfirst used as road metal, burned lirne for sugar refining, and
forthe manufacture of cement. With the increased demand for
cementthe quarrying operations were given or-er entirely to that
purpose.At the present t ime the material is obtained by
underground min-i.g.
PURPOSE AND METHOD OF INVESTIGATION
Although much work has been done on the mineralogy of
theIimestones and associated rocks at Crestmore, never before
hasthe geology been mapped and the mineralogy studied in its
relationto the geology of the district for the purpose of
determining theparagenesis of the minerals and their petrological
associations.With this purpose in mind as a major objective, the
work was con-ducted and resulted in the following related
units:
1. Detailed geologic study of the Crestmore quarries and
theeastern portion of the Jurupa Mountains.
l Eakle, A. S., and Rogers, A. F., Wilkeite, A New Mineral of
the Apatite Groupand Okenite, Its Alteration Product: Am. four. Sci
, vol. 27 , pp. 262-267, 1914.
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JOURNAL MINERALOGICAL SOCIETY OF AMERICA
2. Economic study of a typical Southern California l
imestone
deposit.3. Collection and determination of a large amount of
mineralogi-
cal material by chemical analysis and optical methods.4.
Organization of this material into a catalogue of mineralogical
associations.Unfortunately some of the rare minerals described
from this
locality were entirely removed during the quarrying
operations.Hence in preparing a catalogue of the mineral species it
wasnecessary to take some of the data from the l iterature and in
these
cases the relationships and associations could not be
precisely
determined.The map of the Crestmore quarries was made on the
scale of
I" :100' on a topographic map kindly f urnished by the
Riverside
Cement Company. The hil ls to the west of the quarries
weremapped on a portion of the U.S.G.S. San Bernardino
Quadrangle,originally on the scale of 1":1 mile photographically
enlarged to
1 inch equals one-half mile. Locations were determined by
means
of a Brunton compass and a l ight plane table.
ACKNOWLEDGMENTS
The writer wishes to thank the officials of the Riverside
Cement
Company, Mr. John Treanor, Mr. G. A. Beckett, and Mr. Earl
MacDonald, for their permission to make a geologic map of
the
quarries. Messrs. Thomas Mullan and C. A. Robotham of the
same organization were very helpful. Much credit is due Dr.
Ren6
Engel, of the California Institute of Technology, under
whose
direction this work was conducted, for the help he has
given.
GEOLOGY
The geologic study of the district and the economic aspects
of
the Crestmore l imestones wil l be the subject of another
paper.
However, it is entirely within the scope of the present paper
and
will add materially to its value to give here a brief resum6 of
the
geology. A geologic and topographic map of the Crestmore
quarries
is shown on Plate 1.
Stratigraphy.
The oldest rocks of the Jurupa Mountains form a thick series
of
recrystallized sedimentaries for which the name, Jurupa Series,
is
proposed. The stratigraphically lower part of the section'
consist-
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//,F
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GEOLOGIC MAPOF TTIE
CRESTMORE QUARRIESRIVERSIDE CO., CALIF
F'{PIJI{iATION
AUATERNARY ALLWIUM
rd-"]DUNE SANDS
INTRUSTVE FOCXSPRE -CBETACMUS
mPEGMAIM DITGS
ATZ MONZONITE POFHY}T'
ni$F_qGMN@I]RJE
)ffil/o$#{c-"ffi|i$s.,E N f f i
ffiITE CArcITE Bu CMMSKT BLUE QIARRY UMESrcNE
74KXC}ID{o QURRY CTJAMXT
ffirc QUART{/ U}DSTONE
CONIACT ROCK
NW'ASSOCIATED WIfr Q,}rcNZONITE P.
SYMBOIJCoNTACT, cm-lMru-.-+-
DIP AND aRXE /
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642 THE AMERICAN MINERALOGIST
ing of undifferentiated quartzites, schists and gneisses with
small
l imestone lenses, wil l be referred to as the Undifferentiated
Com-plex. Lying on this complex, with the same attitude and
possibly
conformably, are the l imestones which are exploited for
cement
manufacture. These were differentiated on the large scale map
of
the Crestmore quarries (Plate 1) into the following units: (1)
The
lower, Chino Quarry limestone, (2) Overlying qtartzite and
schist
beds, called the Chino Quarry quartzite, (3) The upper, or
Sky
Blue Quarry l imestone. Granodiorite and quartz monzonite
in-
trusions separate these lower members from the upper l
imestone.
In mapping this last unit an effort was made to trace the l
imits of
the development of the blue calcite. Because of the
uncertain
nature of the outcrops this distribution could not be
carried
through in detail but is indicated in a general way on the
map
(Plate 1) .
T he U ndifer entiated C omPlex.
These rocks are best exposed in the hil ls about two miles
north-
west of Crestmore. The stratigraphic units are tabulated below
in
descending order:
1700 ft. thin bedded quartzite interstratihed with fissile mica
schist.
850 ft. coarse bedded quartzitic schists.
1050 ft. biotite gneiss in part schistose.
100 ft. hard, thick bedded, quartzite in part schistose.
3700 ft. +
Granodiorite cuts off the base of the section and intrudes parts
of
it thus making it impossible to determine the true thickness of
the
section.
The Chino Quarry Limestone.
This l imestone, the best exposure of which is in the
Chinoquarry, is lvhite, medium to thin bedded, and medium to
coarselygranular. Graphitic beds are found throughout the section
but are
more common near the base. Another conspicuous rock type is
the
calcite-brucite rock, or predazzite. Pseudo-isometric crystals
of
brucite occur in beds of medium grained, white l imestone.
Rogers2
2 Rogers, A. F., An American Occurrence of Periclase and its
Bearing on the
Origin and History of Calcite-Brucite Rocks: Am. Jour. Sci.,
vol.46' pp. 582-586,
1918. Periclase from Crestmore near Riverside, California, with
a List of Minerals
from this Locality: Arn Mineral., vol. 14, pp.462469,1929.
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JOURNAL MINERALOGICAL SOCIETY OF A]/IERICA 6+3
has shown that these brucite crystals are pseudomorphs
afterpericlase, remnants of which can sti l l be found enclosed in
thebrucite. Associated minerals are chondrodite, spinel,
magnetiteand wilkeite.
The base of this l imestone has been cut off by granodiorite
sothat the true section cannot be ascertained. The maximum
exposedthickness is of the order of 470 feet. The total would
undoubtedlybe considerably greater.
The Chino Quarry Quartzite.
The structural relations between the Chino Quarry quaftziteand
the Chino Quarry l imestone is not precise. They are in
partseparated by a sil l- l ike intrusion of granodiorite. Where
their con-tact is exposed they are apparently conformable, but the
quartzitehas a shallower dip than the underlying limestone. The top
of thequartzite has been cut ofi by intrusions of granodiorite and
qnartzmonzonite porphyry, except at the eastern end where it
appearsto be unconformably overlain by limestone, but the exposures
arepoor and this relation is not certain. The examination of
diamonddrill cores and the underground workings proves that the
down-ward extension of these rocks is severed by intrusions about
twohundred feet below the surface.
A total thickness of at least 75 feet is exposed. The
formationconsists of interstratified, thin bedded, quartzite and
fissile micaschists.
The Sky Blue Quaruy Limestone.
Except for the development of the blue calcite and the
moreintense metamorphism near some of the quartz monzonite
dikes,this formation is lithologically similar to the Chino Quarry
lime-stone. There is no evidence to show that the original
sediments ofthese two units differed appreciably in chemical
composition. This
study has proven that any differences are directly related to
thevarying degrees of metamorphism to which each limestone has
been subjected.Igneous intrusions have separated the Sky Blue
Quarry lime-
stone from the underlying Chino Quarry quartzite so that
theirrelations can only be inferred. The attitude of the
formationsdiffers appreciably. This may be due to distortion during
intrusion,
or possibly the intrusion followed a line of previous
structural
weakness. i.e.. an unconformitv or a fault.
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6M THE AMERICAN MINERALOGIST
Alluvium covers the top of the section but a thickness of
over500 feet is exposed in the quarries.
Other Outcrops.
In the Jensen quarry to the west and in several other parts
ofthe area studied, outcrops of l imestone are found. They are l
itho-logically similar to the l imestones described above but their
struc-tural relations are so obscure that their further discussion
in thispaper is not warranted.
Age and. Suggested Correlation of the Jurupa Series.
Because of the isolated position of this range and the lack
offossils, correlation had to be based on lithologic similarity. On
thisbasis, the Undifferentiated Complex is thought to be the
equiva-lent of the Arrastre quartzite and the l imestones
equivalent to theFurnace limestone described by Vaughan3 from the
San BernardinoMountains. Vaughan considered the Arrastre qtaftzite
as lowerCambrian and the Furnace limestone as upper Cambrian
andOrdovician. Later work by Woodford and Harrissa proves thatat
least the upper portion of the Furnace limestone is
Mississippian(?). Since it is apparent that the age of similar
rocks is not preciselyknown, the Jurupa Series has been assigned to
the Paleozoic (?)era without attempting to relate it to any
particular period orperiods.
Quoternary Alluoium.
Undifferentiated dune sands, river sands, and fan deposits
aregrouped under this unit.
fcNrous Rocrs
In this region five distinct but related plutonic rock types
arefound. Apparently these types are the result of differentiation
froma parent magma and range from hypersthene quartz diorite
topegmatites.
H y p er sthene Quartz Diorite.
This oldest and most basic rock outcrops on the hil ls
southwest
3 \raughan, F. E., Geology of the San Bernardino Mountains North
of SanGorgonio Pzss'. Bull. Dept. Geol., tlniv. CaliJ., vol. 13,
pp. 319412, 1922.
a Woodford, A. O., and Harriss, R. S., Geology of Blackhawk
Canyon, San Ber-nardino Mountains, California: Bull,. Dept. Geol.,
Unio. CaliJ., vol. 17, pp. 265-304. 1928.
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JOURNAI. MINERALOGICAL SOCIETY OF AMERICA 645
of Crestmore. A microscopic determination shows the
following:
The texture is holocrystalline, medium grained,
hypidiomorphic,inequigranular. The femic minerals are represented
by slightlypleochroic hypersthene, hornblende, in part uralit ic,
and biotite.The feldspar is a basic andesine and shows slight
zoning. Undula-tory quartz was the last mineral to crystallize.
Pyrite and apatiteare the accessories. Near the periphery the rock
shows texturaland mineralogical differences. The texture is
porphyritic. Thephenocrysts are labradorite and the feldspar of the
ground massis andesine. Quartz is less abundant. These variations
can bereadily explained by the different rates of cooling that
would ob-
tain at the center and at the periphery of the mass.
Granodiorite.
It forms the bulk of the intrusive rocks in the area mapped.
Oneof its most characteristic features is the presence of basic
inclusions.These are roughly egg shaped, from two inches to one
foot long,
and are, to some extent, oriented with their long axes parallel
toeach other. The texture and the mineralogical constituents of
theseinclusions show their affinity with the peripheral phase of
thehypersthene quartz diorite from which they were probably tornby
the intruding granodiorite.
A holocrystall ine, coarse to medium grained,
hypidiomorphic,inequigranular texture is characteristic of the
granodiorite. Most
of the femic material is pleochroic hornblende. Chlorit ized
biotiteis present in lesser amounts. Sericit ized oligoclase with
subordinate
amounts of orthoclase constitute the feldspathic elements.
The
abundant qtartz shows undulatory extinction. The accessories
areapatite, zircon and hematite.
Quartz M onzonite Por phyry.
Numerous intrusions of this rock cut the l imestones in the
Crest-more quarries and it is to solutions emanating from these
intrusions
that most of the rare minerals owe their genesis. The texture
isholocrystall ine porphyrit ic, hypidiomorphic, f ine-grained,
inequi-granular. The feldspars are orthoclase and oligoclase both
asphenocrysts and as constituents of the ground mass. They show
alteration to calcite and sericite. Abundant qtartz occurs in
part
in micropegmatit ic intergrowth with the orthoclase.
Scatteredgrains and aggregates of pale green augite constitute the
femic
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THE AMERICAN MINERALOGIST
material. Pleochroic grains and aggregates of titanite are
common.Apatite and pyrite are the accessories.
The peripheries of the larger dikes and of many of the
smallerones exhibit marked endomorphic effects resulting from
theassimilation of foreign material and from more rapid cooling. In
ageneral way these effects are:
(1) Frequent development of porphyrit ic texture.(2) An increase
in the abundance of the ferromagnesium con-
stituents and a change in their character. In this case we
havediopside, diallage, augite, and grossularite.
(3) An increase in the amount and basicity of the plagioclase.(
) In many cases a complete disappearance of quartz.
Granite Porphyry.
The granite porphyry outcrop, in the western portion of the
Jurupa Mountains, is too far removed from the quarries to
meritclose consideration in this paper, but its occurrence is
interestingin its relation to the igneous sequence.
The texture is holocrystalline, medium grained,
porphyritic,hypidiomorphic, inequigranular. Microcline, oligoclase,
orthoclase,qlrartz, biotite, rutile, magnetite and apatite are the
mineralsrepresented.
Pegmatite Dikes.
In the literature on the Crestmore quarries the statement
thatthe pegmatite dikes are abundant and commonly traverse
thelimestone is often made. The writer's observations are at
variancewith this statement for very few of these dikes are seen
and neverin the limestone. It is possible, however, that the dikes
mentionedin the literature were small and were removed during
quarryingoperations.
An abundance of pegmatite dikes occurs in the hills adjacent
tothe quarries. They vary in width from less than an inch to as
muchas twenty-five feet and some of them can be traced for miles.
Manyof these dikes show banding. The outer bands are made up
oflayers, one-half to one inch thick, composed of graphic
intergrowthsof quartz and albite. The inner zone, having a width of
about one-tenth the total thickness of the dike, is composed of
extremelycoarse feldspar and quartz with the occasional development
ofblack tourmaline and biotite. The composition of the
feldsparvaries between albite and microcline.
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JOURNAL MINERALOGICAL SOCIETY OF AMERICA 6+7
Age and Sequence of the Intrusite Rocks.
Intrusions of Jurassic age occur in the Santa Ana Mountains
and in the Julian district. Vaughans correlates the Cactus
granite
of the San Bernardino Mountains with the Jurassic granites of
the
Sierra Nevada but mentions an earlier intrusion which may
belong
to the Paleozoic. Since there is a possibil i ty that the
JurupaMountain intrusives might be earlier than Jurassic their age
is
designated merely as pre-Cretaceous.The sequence of intrusions
has followed the order: hypersthene
quartz diorite, granodiorite, qvartz monzonite porphyry,
granite
porphyry and pegmatite dikes. Their order and spatial
relation-
ship suggest dif ierentiation from the same parent magma and
that the intrusions followed closelY in point of t ime.
Cowracr Rocxs
Three distinct types of contact rockquartz monzonite porphyry
intrusions.the order of their importance.
Garnet Contact Rock.
The face of the Commercial Rock quarry and the crest of Sky
Blue Hil l is made up almost entirely of this material. The
greatest
proportion of the rock is badly fractured massive
grossularite'
Other minerals, in the order of their importance, are
diopside,
diallage, calcite, wollastonite, augite and scapolite.
V esuaianite C ontact Rock.
At the corner of Lone Star, Wet Weather and Commercial Rock
quarries a contact rock consisting chiefly of vesuvianite and
calcite
is developed. The proportions of these minerals vary greatly'
In
places the rock is nearly all vesuvianite, quite massive and
glassy'
at others the calcite and vesuvianite are approximately in
equal
amounts. The other extreme is found when the mass is almost
all
calcite with only a few grains of vesuvianite embedded in it '
The
calcite occurs as a soft, white mass of aggregates of extremely
fine
needles and some very small rhombohedrons. These forms prob-
ably represent rapid crystallization from a supersaturated
solu-
tion. Diopside, garnet and wollastonite are the minerals
commonly
associated with this rock.
5 Vaughan, F.8., Op. cit., 1922.
have been formed by the
These are l i s ted be low in
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648 THE AMERICAN MINERAL)GIST
In several places in the Wet Weather quarry this assemblage
isfound definitely confined to certain beds, thus indicating that
theinitial character of the limestone strata may have been one of
thegoverning factors in its origin. It is interesting to note that
in thiscase the calcite is quite coarsely crystalline.
Quartz and Garnet Contoct Rock.
This rock is composed wholly of granular, vitreous qrartz,
andgrossularite crystals and grains. ft is found close to a small
quartzmonzonite porphyry dike near the outcrop of the Chino
Quarryquartzite in the saddle north of the Chino quarry. This
associationindicates its derivation from an impure l ime bearing
sandstone.
MINERALOGY
It is impossible in this paper to include a complete catalogue
ofthe minerals. Hence, the following descriptions are limited to
newoccurrences or to controversial subjects to which the author
hasnew data to add.
Following this section the minerals are alphabetically
tabulatedin a manner which shows their petrologic distribution,
their rela-tive abundance and, to a large extent, their
associations. For moredetailed information the reader is referred
to the abundant litera-ture on this locality.
Sulphides: Eakleo states that the sulphides are associated
withthe pegmatite intrusives. The author has not found this to be
thecase. Where the association has been seen the sulphides are
con-centrated near the qnartz monzonite porphyry. No sulphides
arefound as accessories in the pegmatites, but they are present
assuch in the quartz monzonite porphyry. fn the author's
opinionsolutions from the quartz monzonite deposited the
sulphidemineralization found in the quarries.
M onticellite: This mineral has been described by Eakle7 from
theblue calcite and later by Til leys from the contact rock. Eakle
sug-gested that the monticellite results from the metamorphism of
thebrucite limestone, while the diopside and vesuvianite were
formedduring the metamorphism of the pure beds. Thus he accounts
for
6 Eakle, A. S., Minerals Associated with Crystalline Linestone
at Crestmore,Riverside County, California: Bull Dept. Geol., Univ.
Cali.J., vol.l0, pp. 327-360,1917.
7 op. cit., 19t7.8 Tilley, C. E., On a Custerite,bearing Contact
Rock from Calilornia: GeoI.
Magozine, pp. 371-372, 1928.
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JOURNAL MINERALOGICAL SOCIETY OF AMERICA 649
the scarcity of monticellite and xanthophyllite. fn an earlier
paperEaklee attributed the formation of these minerals to solution
actionaccompanying the qtartz monzonite porphyry intrusion.
Thewriter's observations confirm the earlier statement by Eakle,
forotherwise it would imply that the brucite l imestone is l imited
inextent, while, on the contrary, it is quite common.
Diallage: Diallage is found in the endomorphic phases of
theqrartz monzonite porphyry, and in the garnetiferous contact
rock.
Orthoclase: According to Eaklelo orthoclase forms the
largerportion of the pegmatite dikes. In the samples examined by
theauthor no orthoclase was found in the pegmatites, only albite
andmicrocline. It does occur, however, in the granodiorite, the
graniteporphyry and the qvartz monzonite porphyry.
Oligoclase: This is the plagioclase feldspar of the
granodioriteand also occurs in the enclaves in the granodiorite. It
is a con-stituent mineral of the quartz monzonite porphyry, the
hypers-thene quartz diorite, the granite porphyry and the
UndifferentiatedComplex.
Labradorite: This has been described by Eaklell as one of
theconstituents of the granodiorite, along with oligoclase. No
evidencehas been found for two generations of plagioclase. The
plagioclaseis entirely oligoclase. Labradorite occurs as
phenocrysts in thehypersthene quartz diorite and in some of the
basic enclaves inthe granodiorite. A few grains were found in the
UndifierentiatedComplex and the Chino Quarry quartzite.
Bytownite-Anorthite: Crystals of plagioclase of the
bytownite-anorthite type were found in a small cavity at the border
of oneof the small qvartz monzonite porphyry dikes in the lower
Chinoquarry. They were associated with pyrite, chalcopyrite
andbornite.
Scapolite: A grey white scapolite with violet streaks has
beenmentioned by Eakle. The material collected by the author is
whiteand composed of small radiating aggregates of extremely
fineneedles, so fine that to the unaided eye the material appears
almostmassive. It occurs in the contact rock associated with
wollastonite,calcite, diopside, and grossularite, surrounding these
minerals andf i l l ing spaces between them. The indices, a:1.567
+.005, e :1.548
eEakle,A.S. ,Xanthophyl l i te inCrystal l ineLimestone:.
/aar.Wosh Acad.Sci ' ,vol . 6, pp. 332-335, 1916.
10 op. cit., l9l7.t1 Op. cit , 1917.
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650 TH E AM ERICAN MINERALOGIST
+.005, measured on one sample would indicate, according
toWinchell'sl2 diagram marialite 600/6, meionite 400/6, or the
speciesdipyr i te . Another sample gave values co:1.504*.005,
e:1.550+.005, which corresponds to the values of a mixture oI
40/emarialite, and 60/6 meionite, or the species mizzonite. This is
anuncommon form of crysta"llization for scapolite. The fine
crystallin-ity would suggest extremely rapid growth of crystals by
rapidcooling of a supersaturated solution. Ifowever, the
associatedminerals are very coarse, so that this condition does not
apply toall of them
Clinozoisite: A pale, transparent to translucent, greenish
greyvariety occurs in shattered crystals and grains in a small
contactmass associated with one of the smaller quartz monzonite
porphyrydikes in the Chino quarry. The associated minerals are
garnet andcalcite. This undoubtedly results from the hydrothermal
actionof solutions from the qtarLz monzonite porphyry on the l
imestone
Epi.dote: Small black crystals, up to three mill imeters in
length,were found disseminated in the white Chino l imestone and
asso-ciated with the deweylite and chrysotile, near a dike ol
qtartzmonzonite porphyry. A green epidote is abundant in some of
thepegmatites as already noted by Eakle.
Xanthophyllite: This mineral was first described from this
lo-cality by Eaklels as disseminated in the blue calcite and
associatedwith monticell i te. The above occurrence was not found
but smallcrystals and flakes were found in a locally developed,
coarselycrystall ine green calcite in the Chino Quarry l imestone
that wasassociated with a small dike oI quartz monzonite
porphyry.
Chrysotile ond. Deweylile.' A massive green mineral was found
inthe white calcite of the Chino Quarry l imestone in East
Chinoquarry, a few feet from a small quartz monzonite dike. An
analysiswas made by Mr. Thomas Mullan of the Riverside Cement
Com-pany and the following results were obtained:
SiOz(Fe, Al)z OaCaOMgoHrOCOz
40.88
5 . 9 13 7 . 5 21 2 . o o2 . 5 0
i00 .0812 Wincheil, A. N , The Properties of Scapolite.: Am.
Mineral, vol. 9, pp. 108-
t r2 ,1924.13 Op. cit., 7977.
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JOURNAL MINERALOGICAL SOCIETY OF AMERICA 651
Calcite grains could be seen in the material so CaCOr and(Fe,
Al)rOa were discarded and the other figures recalculated on
thebasis of 100 per cent.
per cent mol-numbers ratios
sio, 45 .20 7 5 3M g O , . . 4 1 . 5 0 1 0 4 4H,O. 13 .30 .74
3
This gives the formula 3HzO 4MgO.3SiOr, or H6MgaSirOrg,
whichdoes not correspond with any of the known hydrous
magnesium-sil icate minerals. Grains of the material show indices
as follows:A min imum of 1.528*.005, the maximum is 1.555+.005. I f
th iswere one mineral the birefringence would be 0.027, which is
muchtoo great in comparison with the observed birefringence. Thus
it
is thought that this represents a mixture of chrysotile and
dewey-lite. A mixture of these minerals in the proportion 68.8/e
deweyliteand 3L2/6 chrysoti le would give an analysis corresponding
to the
above one. A thin section of the material proved that two
minerals
were present.Rogersla describes deweylite replacing
hydromagnesite in the
calcite-brucite rock, and regards it as a supergene mineral. In
viewof its present relation to the quartz monzonite porphyry dike
it
seems that the genesis of these sil icales can be assigned to
the
action of solutions emanating from this dike on previously
formed
minerals (epidote or diopside as suggested by their nearby
oc-currence) and thus in this case their origin would be
hypogene'
Sepiolite: A white, fibrous mineral was found filling small
veinsin the calcite near the occurrence of the chrysotile and
deweylite.The material is composed of finely interlocked fibers
with the fibers
oriented parallel to the vein walls. An analysis by Mr.
Mullangave the following results:
Sio:(Fe, Al)zOaCaOMso.HzOCOz
Total
44.380 . 8 2
1 1 . 9 020.2413.099 . 4 9
g 'g 'n
The nature of the material made it impossible to free it,
for
analysis, from small grains of calcite so that CaCOa and (Fe,
Al)zOr
were removed and the figures recalculated to 100 per cent.
11 0b. cit.. l9l8
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TH E AMERICAN MINERALOGIST
per centSioz 57.00MeO 26 00HrO. 17 00
mol-number ratios
. . 9 5 . . 3.645 2.945 3
The above ratios correspond to the formula: 2MgO.3SiO,
3HrO.Tlris probably represents a mineral between sepiolite and
para-sepiolite, but since the water content of sepiolite is
variable themineral has been called sepiolite. Optical properties
are:Iy'-:1.510+.005, extinction parallel to the fibers, biaxial
negative, bi-refringence low. It is unattacked by HCl. 1y'- for
sepiolite is 1.52and for parasepiolite 1.506. This mineral has
intermediate opticalproperties as well as composition.
The proximity of this occurrence to the chrysoti le and
deweylitesuggests that the sepiolite represents an alteration
product of theseminerals.
In the following table (Table 1) the minerals are listed in
alpha-betical order. At the right, in vertical columns, are entered
thenames of the predominate rock types of this locality. The
petro-logic distribution and to some extent the relative frequency
ofoccurrence and the relative importance in a rock is indicated,
foreach mineral, by an appropriate letter. This gives a general
con-ception of the mineral associations.
The purpose of this table is to summarize, in a general way,much
of the data on the minerals of this locality. For more
detailedinformation on any mineral the reader is referred to a
paper byRogersls in which a complete bibliography is given.
PARAGENESIS
The present record of the metamorphic history of the l
imestonesshows no efiect of the intrusion of hypersthene quartz
diorite, thefirst member in the suite of intrusions which has
altered theserocks. The spatial relations show that this intrusion
was too faraway to have had any effect other than recrystall
ization and frac-turing resulting from heat and stresses produced
during the in-jection of the magma.
The flow structure, so often found in the granodiorite near
thecontact with the sedimentaries, and the coarse crystall inity of
therock indicates that at the time of intrusion it was very
viscous,
15 Rogers, A. F., Periclase from Crestmore, near Riverside,
California, with aList of Minerals from this Locality: Am.
Minerol., vol. 14, pp. 12,462-469,1929.
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IOURNAL MINERALOGICAL SOCIETY OF AMERICA 653
and cooled slowly, l ikely under great pressure. Its
contribution to
the metamorphism of the l imestone has been: (1) Recrystall
izationand Iurther fracturing of the l imestone. (2) The reduction
of thecarbonaceous material to graphite. (3) With a few exceptions
theformation of the contact metamorphic minerals which are
formedmostly under high pressure and temperature and without
abundantmineralizers. This was accomplished in the following
manner:(a) dissociation of magnesium carbonate to periclase; (b) by
re-action in the impure limestone with the formation of spinel,
mag-netite, grossularite, wollastonite and diopside; (c) probably
at a
Iater stage chondrodite, wilkeite and phlogopite were formed
byhydrous emanations from the magma containing phosphate, sul-phate
and halides. The hydration of the periclase to brucite tookplace,
in part, during the cooling of this intrusion.
The contact metamorphic effects of the quartz monzonite
por-phyry were both endomorphic and exomorphic, but it is with
thelatter efiects that we are principally concerned here, as the
othershave already been briefly discussed. As a consequence of this
in-trusion the l imestones were further fractured and further
re-crystall ized, especially near the borders of the dikes, unti l
in someplaces the previous structures were eliminated. Chemical
changesresulting from heat, pressure and the action of mineralizers
weremore general and more complex than those of the
granodiorite.The most important of these changes from the
standpoint of mag-nitude is the development of the garnetiferous
contact rock. Thisdevelopment is particularly intense above the
dikes where, wemay assume, the action of the mineralizers would be
concentrated.The total destruction in this mass of all previous
structures andits coarse crystall inity indicates a complete
reaction involving thismaterial and slow cooling during subsequent
recrystall izationunder rather uniform pressure. Thus by the
solvent action on animpure l imestone of the sil icate solutions
accompanying the quartzmonzonite porphyry intrusion the formation
of such minerals asgrossularite, augite, diopside, diallage,
wollastonite, scapolite,monticell i te and bytownite-anorthite has
been effected.
The manner in which the vesuvianite-calcite type of rock
isconfined to the outer margins of the contact mass suggests
thatits development was largely determined by physio-chemical
rela-tions in which a lower temperature and favorable
concentrationsin AlzOa and SiOr were important factors.
-
654 THE AMERICAN MINERALOGIST
Tanr,n 1A-AccBssonv Mrxlnlr,; C-Colrlrox; F-Fnnqunxr;
M-CoNsrrrutxr MrNonar,; R-RlnE
MrNEner,s Occunnrmcn Rrlr.qnxs
o€o
(,E
tr
o
N
cd
R
N
c
o!o
an
O
AlbiteAndesineAnglesite
-ApatiteApophylliteAragoniteArsenopyriteAugite.
.Axinite.AzuriteBiotiteBorni te.Bruci
te.Bytownite-AnorthiteCalciteCentrallasiteCerusiteCusterite.Chalcedony.ChalcociteChalcopyriteChloriteChondroditeChrysotileClinochlore.ClinozoisiteCrestmoreiteDatolite.DeweyliteDiallageDiopside.EpidoteFoshagiteGalenaGehleniteGraphiteGrossulariteGreenockiteHematiteHornblendeHydromagnesiteHyperstheneJurupaite
Mnf
A
Alteration of galena
In wollastonite near contaclIn veinlets
Associated with garnetOccurs as stains
In cavities near contactAlteration of periclaseIn cavities near
contact
Replaces quartzAlteration of galena
In cavities near contactIn cavities near contactAlteration of
biotiteDisseminated i n pr edazziteSmall masses near monz. dike
Small masses near contactDisseminated in blue
calciteMassiveSmall masses nearmonz. dike
In veins cutting vesuvianite
Associated with merwiniteDisseminated
Coating sphaleriteAlteration of iron minerals
Alteration of brucite
In cavities in limestone
R
R I RC
M F M
RRRR
R
RRR
RRC(l
R
C
MM
R
MR
CMM
tvl
N
d
a b
F
C C
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JOURNAL MINERALOGICAL SOCIETV OF AMERICA 655
Tesrn 1 (Contintr,ed)
MrNrnar,s Occunnpxcr RBrrelrs
KaoliniteLaumontiteLabradoriteLimoniteMagnetileMalachiteMerwiniteMonticelliteMicroclineMuscovite(Jkenite.OligoclaseOpalOrthoclasePericiasePhlogopitePlazolitePrehnitePyriteQuattzRiversideiteRutileSepiolite
SericiteSphaleriteSpinel
TetrahedriteThaumasiteTilleyiteTitaniteTourmalineUraliteVesuvianiteWilkeiteWollastoniteXanthophylliteZircon..
!o
d
M
pi
N
d
FM
a
RM
AM
p]
N
N o
o
a-F
CF
RR
R
R
F
CR
p
R
FRCR
CFR
R
RR
F
R
FM
Alteration of feldsparCoating prehnite
StainsDisseminated in the PredazziteStainsLarge masses in blue
calcite
Alteration of apophyllite, wilkeite
Enclosed by brucite
In cavities in feldsparDisserninated in limestone
In veinlets in vesrtvianite
In veinlets in predazzite
DisseminatedAssociated with merwiniteIn veinletsIn veins and
coating spurriteAssociated wi th wol laston i l "e
In blue anrl green calcite
-
THE AMERICAN MI I{ERALOGIST
Similar sil icate solutions operating outside of the garnet and
thevesuvianite zones and therefore probably at lower
temperatureswere responsible for the formation of the associated
rare mineralsmerwinite, gehlenite, and spurrite. The fine granular
and theacicular wollastonite were also formed in the outer portion
of thecontact zone.
After the crystall ization of the garnet and vesuvianite
contactrocks and following the high temperature reactions, but in
partcontemporaneous with them, hydrous solutions containing
phos-phates, halides and sulphates found easy access into the l
imestonesand contact rocks along the bedding planes and numerous
frac-tures. This probably represented the latter part of the
pneumato-lit ic stage or the early part of the hydrothermal stage.
By theiraction on the l imestones and on the previously formed
contactrocks they formed various hydrated minerals. It is thought
thatfrom reactions of this type minerals such as epidote,
clinozoisite,wilkeite, chondrodite and custerite were produced. By
furthercooling crestmoreite, riversideite, foshagite, jurupaite and
plazolitewere formed. Crestmoreite, riversideite and foshagite are
probablyalterations of wilkeite.
Deweylite, chrysoti le and sepiolite developed when the
hydro-thermal solutions acted probably on diopside and diallage
orepidote of the contact zone. Xanthophyll ite could have
beenformed either from preexisting sil icates or from the impure l
ime-stone but under the conditions observed in the field it seems
moreprobable that it too is an alteration of diopside or a closely
relatedmineral. The reaction of the sulphated solutions on the
spurriteresulted in thaumasite. Sulphide solutions deposited the
sulphideminerals. ft was in this stage of the hydrothermal action
that thehydration of the periclase to brucite ended.
The metamorphic action of the pegmatite is similar in
manyrespects to that of the quartz monzonite porphyry although
notas intense and with the characteristic development of some
boro-silicate minerals. The first phase is characterized by the
develop-ment in the pegmatite and in small adjacent contact zones
of thecommon wollastonite, grossularite and the hydrous sil icate
epidote.This was followed shortly by apophyllite, prehnite, and the
boro-sil icates, tourmaline, axinite and datolite. During the third
stageapophyllite altered to okenite, prehnite to laumontite, and
central-lasite replaced quartz. Eakler6 mentions okenite as an
alteration
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JOURNAL MINERALOGICAL SOCIETY OF AMERICA o.) /
product of wilkeite, but whether this alteration took place
duringthe hydrothermal stage related to the quartz motzonite
porphyryor during that same stage of the pegmatites is unknown.
Other reactions that have occurred here are entirely
supergene.The iron bearing minerals have yielded hematite and
limonite,galena has altered to cerrusite and anglesite, the copper
mineralsto aztrite and malachite. Circulating waters have
depositedsecondary qrartz, chalcedony, opal, secondary calcite and
aragon-ite. Rogersl7 described hydromagnesite as a supergene
alterationproduct of brucite and deweylite as a supergene
alteration ofhydromagnesite.
SUMMARY
In recapitulating the results of thesepoints are emphasized:
invest igat ions the fo l lowing
Pateozoic(?) sandstones, shales and limestones have been in-
truded and recrystallized by a related series of
pre-Cretaceousplutonic rocks in the order: hypersthene qrartz
diorite, granodi-orite, quartz monzonite porphyry, granite porphyry
and pegmatitedikes. Of these only the granodiorite, the qtartz
monzonite por-phyry and the pegmatite dikes have been particularly
effectivemetamorphic agents.
In the Crestmore quarries the principal effect of the
granodioritehas been recrystallization and fusion. The more potent
quartz
monzonite developed large masses of contact rocks and most
of
the rare minerals found here. The action of the pegmatite has
beensimilar but not as intense.
In the following the contact metamorphic minerals are listed
below the rocks to which thev owe their origin:
Cronod.iorite Qtz.Monzoni,tePorphyry
Graphite GrossularitePericlase AugiteSpinel DiopsideMagnetite
DiallageGrossularite WollastoniteWollastonite Scapolite
16 Eakle, A. S., a1. cit., 1917. Jurupaite, a New Mineral: Am.
M'inerol., vol. 6,pp. 107-109, 1921.
17 Rogers, A. F., An American Occurrence of Periclase and Its
Bearing on theOrigin and History of Calcite-Brucite Rocks: Am.
Joru. Sca., vol.46' pp. 581-586,1918.
Pegmatites
GrossulariteWollastoniteEpidoteApophyllitePrehniteTourmaline
-
658 THE AMERIC.I .Y MII 'ER.I LOGIST
Gronodiori,te
DiopsideChondroditeWilkeitePhlogopiteBrucite
Qtz. Monzonite Porphyry
MonticelliteBytownite-AnorthiteVesuvianiteMerwiniteGehleniteSpurriteEpidoteClinozoisiteWilkeiteChondroditeCusteriteRiversideite
CrestmoreiteFoshagite
JurupaitePlazoliteDeweyliteChrysotileSepioliteXanthophylliteThaumasite
SulphidesBrucite
Pegmalites
AxiniteDatolite
OkeniteLaumontiteCentrallasite
ft should be evident from the preceding pages and the abovelists
that the reactions which took place during and following
theseintrusions were not simple and complete; they were
characterizedby their extreme complexity and recurrence. Thus it is
that manyminerals are polygenetic, not only in that they have been
g.enera.tedby each successive intrusion but they have been formed
during thesame intrusion by derivation from different parent
minerals dueto variations in concentration, pressure and
temperature thatmust have prevailed in a mass of this type and
size. Not only ispolygenesis evident but one finds that the same
minerals yieldvarious alteration products. For example:
wollastonite, a mineralcommon to each intrusion, occurs as four
distinct morphictypes (a fact in itself of genetic significance)
but as shown byDunhaml8 some of the alteration products of this
mineral areti l leyite, gehlenite and vesuvianite. Gehlenite in
turn yieldsgrossularite. We know that all of the grossularite is
not alteredgehlenite and that all of the vesuvianite did not come
from wol-
18 Dunham, K. C., A Note on the Texture of the Crestmore Contact
Rocks:Am. Mineral . , vol . 18, pp. 11,474, 1933
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JOURNAL MINERALOGICAL SOCIETY OF AMERICA 659
Iastonite. We are fairly certain of the intrusion which these
re-actions accompanied but not if they occurred during a later
lowtemperature or a recurrent phase of the intrusion. These and
manyother questions can be answered only by further work.
The following graphically depicts some of the genetic
sequencesas they are known to date.
MgCOr+Periclase-B rucite-HydromagnesiteEpidote and/or
Diopside+Chrysotile and Deweylite-SepioliteWollastonite+ Gehlenite-
Grossulari te
\esuvianiteTilleyite
Wil keiteq-Crestmoreite-R iversideit
eApophyllite>.OkeniteSpurrite+ThaumasitePrehnite+Laumontite
Quartz+Centrallasite
fn studying the literature on Crestmore anent the paragensiseof
the minerals occurring there one finds confusing and
conflictingstatements. Some authors do not distinguish between the
differentcontact zones related to the various intrusions, the
phases of eachintrusion and in one case the nature of the injected
rock has beenincorrectly determined. In short, the tendency has
been to toogreatly simplify the facts and to regard the evidence of
specialcases as representative of the whole. If we are to more
fully under-stand the contact metamorphic phenomena demonstrated
hereit is necessary to take a broader view. It is hoped that this
paperwill serve as a step in the right direction.