University of California Berkeley
DEPARTMENT OF THE INTERIOR-U. S, GEOLOGICAL SURVEY
CHARLES 1). WALCOTT, JMIIKCTOU
THE
MINING DISTRICTS OF THE IDAHO BASIN AND THE
BOISE RIDGE, IDAHO
f
BY
WALDKMAR LINDG-RKTST
WITH A REPORT ON THE FOSSIL PLANTS OF THE
PAVETTE FORMATION
FRANK
, TCNOWLTON
EXTRACT FROM THE EKIHTEEXTII ANNUAL REPORT OF THE SURVEY, 1896-97
1'AIiT III ECONOMIC OEOLOOY
WASHINGTON
GOVERNMENT PRINTING OFFICE
1898
THE MINING DISTRICTS OF THE IDAHO BASIN
AND THE BOISE RIDGE, IDAHO,
BY
WALDEMAR LIISTDGKREN;
if
WITH
A REPORT ON THE FOSSIL PLANTS OF THE PAYETTE FORMATION,
B'Y
617
CONTENTS.
Page.
CHAPTER I. General topography and geology 625
Geographical position 625
Snake River Valley .. _ 625
Literature , 626
Topography 628
Geological history 630
Pre-Tertiary 630
The Payette formation 632
Early Neocene volcanic activity 634
Post-Payette erosion ... 635
Post-Payette orographic disturbances 635
Late Neocene basalts ... 636
Post-basaltic erosion.. ,. 636
Resume of geological events in the lower Snake River Basin 637
CHAPTER II. The ore deposits in general 638
General features 638
Alteration of the country rock _ ._. 638
Silicification ... 645
Structure of the veins. ... 647
Mineral deposits of post-Neocene age . _ _ 648
CHAPTER III. The Idaho Basin 651
Geographical position ... 651
Discovery and history ,-. 651
Production . 652
Topography.. 656
Grades of the water courses . .' 657
Tertiary and Pleistocene formations 657
Lower Moore Creek Valley .... . 657
Configuration of valley . 657
The basalt flow 658
The present stream gravels .... 658
The gravels below the basalt 658
High gravels . 659
Upper Moore Creek Valley. . 659
Configuration of valley ... 659
The present stream gravels 660
Bench gravels _. . 660
High gravels 662
Lake beds 665
Gold in the lake beds 668
Olivine basalt (dolerite) _. - 669
The valley of Grimes Creek 669
Configuration 669
619
620 CONTENTS.
CHAPTER III Continued. Page.
Tertiary and Pleistocene formations Continued.
The valley of Grimes Creek Continued.
Present stream gravels.. 670
Bench gravels - 670
Older gravels 671
Lake beds 671
Volcanic rocks - 672
The valley of Granite Creek 672
Configuration ...-_, 672
Present stream gravels 672
Bench gravels .- 672
Older gravels.. 673
Gravel on the Boise Range 675
Basalt _ '.... 675
Fineness of the gold 676
Water supply... : 676
Moore Creek 676
Grimes Creek ... 677
Granite Creek 677
Ground available for future work ... 677
The monazite sands 677
Relation between placers and quartz veins 680
CHAPTER IV. The Idaho Basin (continued) 681
The pre-Tertiary rocks ^. 681
Granite - 681
Dikes associated with the granite 682
The quartz veins 684
The Idaho City gold belt 684
The Elaine vein 684
The Chickahominy vein. 684
The Illinois vein 684
The Populist vein 685
The Cleveland vein... 685
The Gambrinus (Surprise) vein 686
The Boulder vein 686
The Mona MacCarthy vein. 687
The Sub-Rosa or Forest King vein 687
The Elkhorn vein... 689
The Summit vein 689
The Quartzburg-Grimes Pass gold belt 689
The Ebenezer vein.. .". 690
The Gold Hill vein 691
The Iowa vein 692
The Carroll veins ..._.- 692
The Kennebec claim 693
Veins at head of Wolf Creek 693
The veins in the porphyry dike east of Wolf Creek 693
Claims near Grimes Pass _. 694
Mining districts east of the basin 695
Fineness of the quartz gold 696
The geological history of the Idaho Basin 696
CHAPTER V. The mining districts of the Boise Ridge 699
Neal mining district 699
CONTENTS. 621
CHAPTER V. The mining districts of the Boise Ridge Continued. p age .
Neal mining district Continued.
Location 699
Topography 699
Geology 700
The veins 701
Black Hornet mining district 703
Topography 703
Geology 704
Mineral deposits. 704
Boise mining district 705
Shaw Mountain mining district. 707
Mining districts of Willow Creek and Rock Creek 707
Location and topography 707
Geology 708
Granitic rocks 708
Dike rocks 710
The Payette formation 711
Rhyolite. 712
Basalt 712
The ore deposits. 712
General character .. , 712
Treatment of the ores 714
Detailed description 714
Silver deposits .. 718
Placers of the Boise Ridge 718
Recent placers : 718
Neocene placers 719
APPENDIX: The fossil plants of the Payette formation, by F. H. Knowlton. 721
Systematic enumeration of species 721
Discussion of the flora and its bearing on the age of the beds 735
ILLUSTRATIONS.
Page.
PLATE LXXXVII. General map of the lower Snake River Valley, Idaho-... 625
LXXXVIII. Head of Boise Valley, 8 miles southeast of Boise, look-
ing northwest, showing basalt table and Pleistocene
terraces 632
LXXXIX. Upper canyon of . Brainard Creek, Jerusalem Valley,
Boise Ridge, showing tilted basalt flows resting on
granite 636
XC. Types of gold-bearing fissure veins GoO
XCI. The Idaho Basin, looking east from the Jerusalem Road
west of Quartzburg __ 656
XCII. Lower Valley of Moore Creek, 3 miles above its mouth,
showing basalt flow cut through by the creek 658
XCIII. Idaho City from Gold Hill, looking southwest, showing
tailings and bench gravels 660
XCI V. Working bench gravels by the hydraulic process at Idaho
City 662
XCV. Gravel bank with underlying lake bed at Plowman's
claim, East Hill, Idaho City, looking southwest 664
XCVI. Geological map of the Idaho Basin In pocket
XCVII. Map of the Neal mining district, by F. D. Howe 700
XCVIII. Map of the Willow Creek and Rock Creek mining dis-
tricts 708
XC1X. Fossil leaves, Pay ette beds 738
C. Fossil leaves, Payette beds 740
CI. Fossil leaves, Payette beds 743
GIL Fossil leaves, Payette beds 744
FIG. 55. Gravel benches, 1 miles below Idaho City 681
56. Section of highest bench, 1 J miles below Idaho City 662
57. Section across lake beds and gravels at Idaho City 663
58. Exposure of lake beds and auriferous gravel, l miles south of
Idaho City. 665
59. Bench gravel and lake beds at mouth of Granite Creek, 2 miles
west of Idaho City 666
60. Bank of bench gravels, one-fourth mile north of Pioneerville,
level of Grimes Creek 671
61. Bank at the Ranch Company's claim, Placerville 674
62. Diagram of fault in the Cleveland vein 686
63. Section of Mountain Chief vein, east end of claim 690
64. Breast of drift, Carroll vein 693
65. Cross section of vein in the Neal mining district 701
623
THE MINING DISTRICTS OF THE IDAHO BASIN AND THE
BOISE RIDGE, IDAHO, 1
By WALDEMAR LINDGREN.
CHAPTER I.
GENERAL TOPOGRAPHY AND GEOLOGY.
GEOGRAPHICAL POSITION.
The region shown in PI. LXXXVII includes a portion of the lower
Snake River Valley and the mountains adjacent on the northern side.
The total area is about 13,500 square miles. It embraces, besides a
part of the Snake River, almost the whole drainage of the Payette,
Boise, and Wood rivers, and, in the northeastern corner, a part of
that of the Salmon River. The irregular mountain complex within
the drainage of the Boise and the Payette rivers is designated the
"Boise Mountains; " along the parting between these rivers and the
Salmon River drainage rise a series of sharp peaks, usually referred
to as the " Sawtooth Range." The " Boise Ridge " extends from the
Boise to beyond the Payette just west of longitude 116, and attains
elevations of over 7,000 feet. The Idaho Basin is an interniontane
valley in the Boise Mountains south of latitude 44 and east of longi-
tude 116.
The map shows the positions and names of the quadrangles repre-
sented by the topographic sheets issued by the United States Geolog-
ical Survey. It also shows, in a somewhat generalized way, the geology
of a part of the area.
SNAKE RIVER VALLEY.
The discussion of the geology of this district necessitates a short
reference to the large Snake River Valley and an abstract of previous
work relating to its remarkable geological features. The Snake River
Valley stretches across the whole width of southern Idaho in a broad
curve opening toward the north and having a radius of 160 miles. The
length of this valley from the base of the Tetons to Weiser, where the
river enters into a narrow canyon, is over 400 miles, while its width
1 The field work upon which this report is based was done during the summer and fall of 1896
by the author, assisted by Dr. E. C. E. Lord.
18 GEOL, PT 3 40 625
626 IDAHO MINING DISTRICTS.
ranges from 50 to 125 miles, its total area being about 34,000 square
miles. The grade of the river is moderate. At Blackfoot the eleva-
tion is 4,505 feet, and 350 miles lower down, at Weiser, it is 2,125 feet,
giving an average grade of less than 7 feet per mile between these
places. On both sides of this. valley rise higher ranges, chiefly of
granite in the lower valley, of granite and Paleozoic and Mesozoic
rocks in the upper valley. The lower slopes of these ranges are often
flanked by Tertiary lake deposits. The larger part of the valley is
occupied by vast flows of basalt, frequently resting upon and covered
by fluviatile and lacustrine accumulations contemporaneous with the
flows. The basalt of the Snake River Valley bears evidence of being
throughout of the same age approximately, though consisting of a great
number of individual flows, and has generally been regarded as Plio-
cene. The eruptions did not originate from large volcanoes. Ashes
and other fragmentary rocks are generally absent, and the basalt evi-
dently flowed out quietly and without explosions from numerous local
vents along the margin of the valley or within the valley itself. This
volcanic action is usually referred to as fissure eruption, but it must not
be inferred that these fissures were long or large. It appears rather as
if the vents had the character of rounded local orifices, hardly exten-
sive enough to be classed as fissures. The basalts often flowed down
from the foothills of older rocks, closely following the present can-
yons, though the streams have since then generally succeeded in
wearing through the filling in their bottoms. Thus it is, for instance,
along the Boise River.
It will be shown that the Snake River Tertiaries consist of a thick
series of early Neocene (Miocene) lake beds, with which are associated
vast masses of eruptives distinct from the Snake" River basalts proper,
and another series of deposits of late Neocene age (Pliocene), consist-
ing of the Snake River basalts and associated sedimentary rocks.
These two terranes represent successive stages of the Neocene lake
and are often difficult to separate.
LITERATURE.
The upper Snake River Basin has been described by Messrs.
Hayden, 1 Bradley, 2 Peale, 3 and St. John, 4 in the reports of the United
States Geological and Geographical Survey of the Territories.
Hayden describes the basalt flow along the present line of the Utah
and Northern Railroad, mentioning that there were several flows of
basalt, or at least two, separated by somewhat tilted Pliocene depos-
its of slight depth. St. John and Peale describe the basalt flows east
of this, near the headwaters of the Snake River. Peale states that a
number of extinct craters exist, that there were several flows of
1 U. S. Geol. and Geog. Surv. Terr., Kept. 1871, pp. 25-30.
2 Ibid., Kept. 1872, p. 190.
3 Ibid., Rept. 1877, p. 543.
4 Ibid.,Eept. 1877, p. 323.
LINDOREN.] SNAKE RIVER VALLEY. 627
basalt, and that the basalts are generally horizontal in position and
fill the valleys and the more depressed portions of the basins. There
appear to have been two periods of basaltic flows, one at the close of
the Pliocene, the other at the beginning of the Pleistocene. The
Pleistocene age is inferred from exposures at Marsh Valley, near
Red Rock Pass, where Pleistocene beds were somewhat eroded before
the basaltic flow.
According to Gilbert, however, this Pleistocene is older than the
highest stage of Lake Bonneville, during which the lake found an
outlet at Red Rock Pass. The river draining the lake at this time
appears to have flowed over the surface of the basalt.
According to Hague, 1 the latest eruptions in the Yellowstone
National Park are of basalts, which stretch far into Idaho in somber,
monotonous beds. These basalts are pre-Glacial, and their eruption
is referred to the Pliocene.
About 1869 Mr. Clarence King visited the lower part of the Snake
River basin and collected a number of fossils from beds beneath the
basalt at Castle and Sinker creeks, tributaries from the south, joining
the river about due south of Boise. The fossils have been described
in detail, while no description of the localities was ever published, a
fact which has led to some confusion. A few notes regarding this
occurrence are contained in King's Systematic Geology 2 and may be
quoted :
In the basin of Snake River . . . there were basaltic eruptions in the middle
of the Pliocene period which overflowed the earlier lacustrine beds of the period,
and in turn were themselves overlaid ... by the main, later Pliocene series.
. . . Sections obtained along the plains between the Owyhee Mountains and Snake
River show that a considerable portion of the beds of the valley, which consist
chiefly of white sands and marls carrying numerous well-defined Pliocene forms,
were overlaid by large accumulations of basaltic flow, and that subsequently a
second period of lacustrine deposition took place, likewise characterized by Plio-
cene forms, the latter representing a more advanced stage of development and
more recent type than those beneath the basalt.
King further states that near Shoshone Falls the basalt rests on
the eroded surface of a trachytic soft rock which he considers of pre-
Miocene age. 3 From the collections of King and the later collections
of Wortman, Cope has described an extensive fauna of fresh-water
fishes, and proposed for the sediments in which these are contained
the name Idaho formation.*
The locations given are very vague, as "Catherine Creek," " Castle
Creek," or "Southern Idaho," and no description of the beds is
vouchsafed. The fauna consists of 22 species, all differing from
existing species so far as known. Professor Cope thinks that the
1 Am. Jour. Sci., 4th series, June, 1896, Vol.1, p. 455.
U. S. Geol. Expl. Fortieth Par., Vol. 1, 1878, pp. 418, 440.
a Ibid., p. 593.
t Proc. Phila. Acad. Sci., 1883, pp. 153-166.
628 IDAHO MINING DISTRICTS.
evidence clearly indicates a Pliocene age. From the same beds
were obtained three species of crawfishes specifically distinct from
all others described from the West. Mammalian remains were also
collected by King from similar beds on Sinker Creek, which were
determined by Leidy to be Mastodon mirificus and Equus excelsus,
both of which belong to the Niobrara Pliocene fauna. A few mol-
lusks have also been found in the same deposits on Sinker Creek.
Thus Meek 1 described Sphaerium (?) idahoense Meek from Castle
Creek, collected by King. Gabb 2 described two species, Melania
taylori Gabb and LHhasia antiqua from a "Deposit on Snake River
on the road from Boise to the Owyhee mining country;" thus probably
from Walters Ferry. The same forms have been found, according
to Mr. George II. Eldridge, at Glenns Ferry, 120 miles above Walk-
ers Ferry. Dr. White describes the same two species and another,
Latia dallii, from a point 50 miles below Salmon Falls, Snake River,
which probably refers to Glenns Ferry, and states that these forms
differ considerably from any known fresh-water fauna of America
either fossil or living. 3 Both Meek and White are in favor of corre-
lating these Tertiary beds with King's Truckee Miocene. To this the
utterances of King are directly opposed, and it is, indeed, from
stratigraphic grounds, improbable that these beds are of Miocene
age. Near Glenns Ferry beds of sand and clay occur intercalated
between the basalt flows, and it is probable that the fossils came from
this locality and that all of them were collected in beds very closely
associated with the late basaltic eruptions, from which it would
follow that they should be placed in the latest Pliocene.
Prof. O. C. Marsh states (oral communication, January, 1897) that
a large amount of Pliocene mammalian remains was found in a bluff
about 100 feet above the Snake River, some distance below Weiser, at
the old crossing of the stage road to Oregon, on the Oregon side of the
river.
None of these localities were visited during the field season of 1896
on account of pressing economical and areal work in other sections ;
but from the area studied it was possible to read in its chief features
the later geologic history of the lower part of the Snake River basin.
The correlation of these results with the older work remains for the
future.
TOPOGRAPHY.
The chief topographic features of the region, of which the geology
is shown on PI. LXXX VII, are as follows :
Broad flat mesas of basalt and Pliocene lake beds spread on both
sides of Snake River, though chiefly on the northern side. Through
these mesas the river has cut an abrupt canyon, bordered by basaltic
1 Proc. Phila. Acad. Nat. Sci. 1870, p. 57.
3 Paleontology of Gal., Vol. II, p. 13.
' Proc. U. S. Nat. Mus. 1882, Vol. V, p. 99.
UNI-"!";*.-! TOPOGRAPHY OF THE REGION. 629
cliffs, to a depth of from 200 to 700 feet. The low mesas, surmounted
by several buckles or domes of basalt a few hundred feet high, rise
gradually toward the edge of the mountain. Near the mouth of the
Boise River the basalt mesas cease, and from here down to Weiser,
where the great Snake River canyon begins, several large tributaries
enter, such as the Payette and the Owyhee, and, at elevations of from
2,200 to 2,700 feet, level bottom lands and broad low terraces flank
the water courses.
Between the mouth of the Boise and Weiser flat-topped hills of soft
sandstones rise on both sides of the Snake River to a height of 600 to
800 feet. Similar complexes of higli sandy mesas rise between the
lower courses of the Boise and the Payette and north of the Payette.
The mountains of older rocks surrounding the tectonic trough of the
Snake River Valley rise gradually, on the north side of the river,
beyond the sloping mesas of Tertiary rocks, their margin having a
northwesterly direction in this vicinity. The transition between
mountains and mesa is abrupt only at the Boise River, near Boise,
and the abruptness is here due to the extensive erosion of the Payette
sandstones by the river.
The mountain region extending up to the Sawtooth Range, dividing
with a north-northwesterly trend the waters of the Boise and the south-
ern branches of the Payette from those of the Salmon, has an average
width of 5,5 miles and culminates in summits with an elevation of from
10,000 to 11,000 feet. This mountain complex, which is made up chiefly
of granitic rocks, does not form a well-defined range, but rather a
broad uplift dissected deeply and in the most intricate manner by the
forks of the Boise and the Payette. The summits of the narrow ridges
generally form gently sloping lines. If a surface were constructed
containing all these lines it would be of undulating, curved character,
sloping gently from elevations of 9,000 down to 4,000 feet. From the
southwestern edge a steeper slope carries the granitic rocks below the
surface of the Tertiary rocks of the Snake River Valley. The can-
yons of the Boise and the Payette have cut down in the uplift to a
maximum depth of 3,000 feet, and are joined by deep lateral canyons,
dividing the whole region into a maze of narrow aretes. The grade of
the main rivers is relatively low, from 10 feet up to 50 feet per mile,
and only well up toward the head waters are grades of 100 feet per
mile attained. The grades of the lateral canyons are also often rela-
tively slight in their lower course, but extremely steep cirques rise
near their head waters. The Idaho Basin quadrangle offers excel-
lent illustrations of these relations, which are the result partly of a
considerable antiquity of the drainage, partly of the crumbling char-
acter of the granite. At the main divide (Bear Valley quadrangle)
the broad valleys and gentler slopes of the Salmon River drain-
age contrast strongly with the deeply incised canyons of the Boise
and Payette. The latter streams are continually capturing territory
630 IDAHO MINING DISTRICTS.
belonging to the former, and the divide is in process of migration north-
eastward. The whole region may be regarded as an uplifted sloping
plateau deeply dissected by a drainage system, whose origin evidently
antedates the Miocene period. Smaller individual ranges occur in a
few places, as in the Boise Ridge, rising to elevations of 7,500 feet
and extending due north, dividing the Idaho Basin from the waters
of the Payette. This range also crosses the South Fork of the Payette
and continues for some distance north of it. Within this mass of
mountains several depressions or basins with gentler slopes also exist,
such as the Idaho Basin, the Dead wood Basin, and Smiths Prairie,
which have been created or emphasized by more recent orographic
movements. Evidences of glacial topography occur only near the
Sawtooth and Trinity mountains. 1 The lower area here specially
described has never been covered by ice.
GEOLOGICAL HISTORY.
The vicinity of Boise River, where it debouches from the mountains,
proved to be an exceptionally fortunate location for the study of the
geological history of this part of the Snake River drainage, for the
record left by the river of successive geological events back to a cer-
tain date is remarkably clear and easy to read.
PRE-TERTIARY.
The oldest rock exposed is the granite of the Boise Mountains. This
forms an extremely large area, embracing, so far as known, the whole
of the upper drainage of the Boise and Payette rivers and extending
northeastward beyond the Sawtooth Mountains and eastward as far
as Wood River, where it is adjoined by sedimentary rocks of probr
ably Carboniferous age. 2 This rock is largely a typical, coarse gran-
ite of gray or yellowish-gray color, consisting of orthoclase in often
large crystals, plagioclase, quartz, biotite, and sometimes muscovite.
Pegmatite dikes are common in many places. Locally the granite
contains hornblende, and is by gradual transition connected with
intermediate rocks standing between granite and diorite, and also,
though more rarely, with diorites. Narrow dikes of light-colored
granite-porphyry and dark lamprophyric dike rocks, chiefly minettes,
are abundant and present a great variety of structural types. A belt
characterized by dikes of coarse quartz-diorite, porphyrites, and occa-
sional occurrences of gabbro and diabase extends, with one short inter-
ruption, from the vicinity of Wilson Peak, east of the Idaho Basin, by
Quartzburg, to the Willow Creek mining district. All of these dikes
are probably connected with the granite eruption that is, they were
intruded shortly after the consolidation of the granite. Within the
area described the granite is remarkably unaltered and massive, no
1 George H. Eldridge, Sixteenth Ann. Kept. U. S. Geol. Survey, Part II, 1895, p. :*>:!.
2 George H. Eldridge, loc. cit.
LINDOKEN.] PRE-TERTIARY ROCKS. 631
bodies of schist appearing in connection with it. It weathers easily
and crumbles to a coarse sand which largely covers the hillsides.
Only in the higher mountains and along the bottom of the canyons
are satisfactory exposures found. The age of this granite, which is
clearly of igneous and intrusive origin, is an open question. Messrs.
Becker 1 and Eldridge 2 assign to it provisionally an Archean age, but
a thorough study of its contact with surrounding formations is neces-
sary before its age can be determined. The granite is in many places
traversed by shear planes, giving it a jointed or sheeted structure,
and often these planes coincide with the direction of the fissures on
which mineral veins occur. It is probable that these two features
are of the same and contemporaneous origin. Nearly all of the pri-
mary mineral deposits are contained in the granite or allied porphy-
ries. By far most of them have a direction ranging from E.-W. to
ENE.-WSW., and dip to the south at angles from 40 to 85 from the
horizontal. While it is probable that all of them belong to the same
period of formation, there are few definite clews to their age. It is
likely, however, that they are post-Carboniferous, and it is certain
that they antedate the Miocene lake deposits. A Cretaceous or early
Tertiary age may provisionally be assigned to them. The mode of