The Geology and Mineral Deposits 

of Part of the Western Half of the 

Hailey 1°×2° Quadrangle, Idaho

By Earl H. Bennett

U.S. Geological Survey Bulletin 2064-W

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the Idaho Geological Survey,

Idaho State University, and the University of Idaho

with a section on The Neal Mining District

By Thor H. Kiilsgaard and Earl H. Bennett

and a section on The Dixie Mining District

By Thomas M. Jacob
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

This publication is only available online at:

http://geology.cr.usgs.gov/pub/bulletins/b2064-w/

Any use of trade, product, or firm names in this publication

is for descriptive purposes only and

does not imply endorsement by the U.S. Government

Version 1.0 2001

Published in the Central Region, Denver, Colorado

Manuscript approved for publication April 20, 2001

Graphics by authors

Photocomposition by Gayle M. Dumonceaux
Contents

Abstract ......................................................................................................................................... 1

Introduction ................................................................................................................................... 1

Geology .......................................................................................................................................... 1

Major Rock Units ............................................................................................................... 1

Metamorphic Rocks................................................................................................. 1

Rocks of the Idaho Batholith .................................................................................. 3

Tertiary Intrusive Rocks .......................................................................................... 3

Dike Swarms ..................................................................................................... 4

Challis Volcanic Group ............................................................................................ 7

Idavada Volcanics.................................................................................................... 7

Lacustrine Deposits ................................................................................................. 8

Basalts and Gravel Deposits .................................................................................. 9

Alluvial Deposits ....................................................................................................... 12

Structure ............................................................................................................................. 12

Cretaceous Tertiary(?) Compression and Extension(?)...................................... 13

House Mountain Decollement........................................................................ 13

Chimney Peak.................................................................................................... 13

Old Pine-Dixie Gulch Hot Springs Road Orthogneiss................................. 15

Cow Creek Fault................................................................................................ 15

Mylonite near Hall Gulch................................................................................. 15

Thrusting and the Batholith .................................................................................... 17

Eocene Extension ..................................................................................................... 17

Eocene and Older, Normal Northeast-Trending Faults ............................. 17

Regional Northeast Structures and Trends................................................. 17

Brittle Deformation........................................................................................... 19

Basin and Range Extension .................................................................................... 19

North-Trending Faults...................................................................................... 20

Geologic Summary ............................................................................................................ 22

Mineral Deposits .......................................................................................................................... 22

Periods of Mineralization ................................................................................................. 22

Late Cretaceous-Paleocene Deposits .................................................................. 22

Eocene Deposits....................................................................................................... 23

Possible Miocene and Younger Deposits ........................................................... 24

Neal Mining District by Thor H. Kiilsgaard and Earl H. Bennett ............................... 24

Production ................................................................................................................. 24

History ........................................................................................................................ 24

Homestake, Hidden Treasure, and Daisy Mines......................................... 26

Golden Eagle Mine ........................................................................................... 26

Other Properties ............................................................................................... 26

Geologic Setting ....................................................................................................... 26

Principal Veins .......................................................................................................... 27

Other Veins ................................................................................................................ 27

Comparison of Veins of the Neal Mining District With Those of the

Quartzburg and Yuba Mining Districts.................................................................. 28

Mineral Exploration of the Neal Mining District in the 1980’s........................... 28

III
Figures

1. Location map of the western half of the Hailey 1°×2° quadrangle, Idaho.......... 2

2. Generalized geologic map of the western half of the Hailey 1°×2° 

quadrangle, Idaho ........................................................................................................ 4

3-19. Photographs showing:

3. Typical biotite granodiorite terrane in the Mayfield Peak 7.5-minute

quadrangle, Idaho ................................................................................................ 5

4. Ridge north of Evans Creek, Anderson Ranch Reservation area, Idaho..... 6

5. Cat Creek summit, Idaho ..................................................................................... 6

6. Tertiary monzodiorite containing inclusions (enclaves) near the

Iron Mountain Lookout ........................................................................................ 7

7. Looking northwest from just west of Smokey Dome, Idaho .......................... 8

8. Dike of unknown age, Thomson Ranch on Bowns Creek .............................. 9

9. View into the South Fork of the Boise River near Dawes Creek, Idaho ...... 10

10. Landslides in gravels of Mennecke Creek west of the 

Danskin Bridge, Idaho.......................................................................................... 10

Daisy-Homestake-Mountaineer Area ........................................................... 28

Golden Eagle Mine ........................................................................................... 28

Confidence Mine............................................................................................... 28

Sunshine Mine .................................................................................................. 29

Blacks Creek Prospect .................................................................................... 29

Pine (Pine Grove) Mining District.................................................................................... 29

Franklin Mine............................................................................................................. 29

Mountain View (Bonnie Anna) Mine ..................................................................... 30

Skeleton Creek Mining District........................................................................................ 30

Featherville Mining District .............................................................................................. 31

Rocky Bar Area (Rocky Bar, Spanish Town, Bear River, and

Red Warrior Districts......................................................................................................... 31

Production.................................................................................................................. 31

Geologic Setting........................................................................................................ 32

History......................................................................................................................... 32

Marsh Creek Mine.................................................................................................... 32

Prospects North of the Bonaparte Mine .............................................................. 32

Ophir Mine ................................................................................................................. 32

Other Occurrences in the Rocky Bar Area........................................................... 32

Lime Creek Mining District ............................................................................................... 32

Volcano Mining District .................................................................................................... 33

Dixie Mining District by Thomas M. Jacob.................................................................... 33

Geologic Setting........................................................................................................ 33

History and Production ............................................................................................ 33

Other Mines In or Near the Dixie Mining District................................................ 37

Roaring River Mining District........................................................................................... 37

Other Mines in the Study Area ........................................................................................ 37

References..................................................................................................................................... 37

IV
V

11. Indurated tilted gravels on east side of Mennecke Creek, Idaho................. 11

12. Gravels below basalt in Mennecke Creek, Idaho............................................ 11

13. Cow Creek fault, older gravels, and younger gravels in

 Mennecke Creek , Idaho ...................................................................................... 12

14. Basalt lava flow from the Red Mountain vent along Fall Creek, Idaho, 

north of Fall Creek Lodge ..................................................................................... 13

15. Orthogneiss and sheared biotite granodiorite and aplite and pegmatite 

dikes that are intruded by undeformed aplite and pegmatite dikes ............. 14

16. Sheared poker chip biotite-hornblende grandiorite north of 

Chimney Peak on Salix Creek, Idaho ................................................................. 14

17. Orthogneiss and sheared biotite granodiorite on the old Pine to 

Dixie Gulch Hot Springs road, Idaho.................................................................. 15

18. Cow Creek fault near the top of the Cow Creek grade ................................... 16

19. Outcrop between Mennecke Creek and Cayuse Creek, Idaho..................... 16

20. Radar image of the Hailey 1°×2° quadrangle, Idaho............................................... 18

21-23. Photographs showing: 

21. Anderson Ranch Dam, Idaho .............................................................................. 20

22. Elk Creek fault (segment of the Deer Park fault) on the James Creek

road from Rocky Bar to Atlanta, Idaho .............................................................. 21

23. Hot Creek fault, just north of the Elk Creek segment of the 

Deer Park fault, Idaho ........................................................................................... 21

24. Map showing location of selected mineral deposits and mining districts

in the western part of the Hailey 1°×2° quadrangle, Idaho ................................... 23

25. Location map of the Neal mining district, Idaho ..................................................... 25

26. Mine workings of the King shaft in the Dixie district, Idaho ................................. 34

Tables

1. Gold and silver production from mines in the Neal district, 1902–present.......... 25

2. Gold and silver production from mines in the Rock Bar area, 1902–present ...... 31

3. Tonnage and grade calculations for the King shaft ................................................ 35

4. Assay results of ore mined in the King shaft winze near the 300 foot level ........ 36

5. Assay results of material gleaned from the dumps of the King shaft................... 36

Metric Conversion Factors

Multiply By To obtain

Miles 1.609 Kilometers

Feet 0.3048 Meters

Inches 2.54 Centimeters

Tons 1.016 Metric tons

Short tons 0.907 Metric tons

Troy ounces 31.103 Grams

Ounces 28.35 Grams
1

Geology and Mineral Deposits of 

Part of the Western Half of the 

Hailey 1°×2° Quadrangle, Idaho

By Earl H. Bennett

Abstract

Rocks in the western half of the Hailey 1°×2° quadrangle 

of south-central Idaho include various units of the Atlanta lobe 

of the Idaho batholith (biotite granodiorite to two-mica granite) 

of Cretaceous age and plutons and dikes of Tertiary (Eocene to 

Miocene) age that intrude the batholith. Eocene plutonic rocks 

consist of a bimodal suite of anorogenic granite and tonalite-granodiorite and hypabyssal rhyolite and rhyodacite dikes. Rocks 

of the Eocene Challis Volcanics are scarce in the map area but 

are widespread to the east. Rhyolite ash flows of the Miocene 

Idavada Volcanics and basalt of the Snake River Plain crop out 

in the southern part of the area. Lacustrine rocks of probable 

Eocene to Holocene age are present in the vicinity of Anderson 

Ranch Reservoir. Quaternary basalts and gravels are widespread on the South Fork of the Boise River, and alluvial deposits are common along active drainages. Metasedimentary rocks 

of unknown age crop out on House Mountain, Chimney Peak, 

and on the ridges east of Anderson Ranch Reservoir. 

Older structures in the Idaho batholith include a major fault 

beneath House Mountain that may be a decollement for one of 

the large thrust sheets in eastern Idaho or part of an extensional 

core complex. The southern part of the Atlanta lobe of the Idaho 

batholith is cut by northeast-striking faults (parallel with the 

Trans-Challis fault system) that are related to Eocene extension 

and by northwest-oriented faults that formed during basin and 

range extension in the Miocene. The basin and range faults have 

prominent scarps typical of basin and range topography. The 

combination of northeast and northwest faults has broken the 

batholith into a series of rhomboid blocks. Some of these northeast and northwest faults are older structures that were reactivated in the Eocene or Miocene, as indicated by Ar40/Ar39 dates 

on mineralized rock contained in some of the structures.

The Idaho batholith and associated rocks in the map area 

host several hundred mines and prospects in 18 mining districts. 

The deposits range in age from Cretaceous to Eocene, and many 

were developed for precious metals. Most of the deposits are in 

quartz veins in shear zones in granitic rocks of the batholith. 

Several districts were actively being explored for low-grade, 

bulk-minable, precious-metal deposits in the late 1980s and 

early 1990s.

Introduction

The geology of most of the western half of the Hailey 

1°×2° quadrangle in south-central Idaho was mapped and the 

mineral deposits studied from 1984 to 1988 as part of the U.S. 

Geological Survey Conterminous United States Mineral Assessment Program (CUSMAP). The Idaho Geological Survey participated in this program, concentrating on the southern part of 

the Atlanta lobe of the Idaho batholith. 

This paper describes the geology and mineral deposits in 

Elmore County, south-central Idaho between the western edge 

of the Hailey 1°×2° quadrangle (long 116° W.) and Smoky 

Dome (long 115° W.) and roughly between the Snake River 

Plain to the south and the Middle Fork of the Boise River to the 

north (fig. 1). The Boise River (North, Middle, and South 

Forks) is the major drainage. Towns in the area include Featherville, Pine, Prairie, and Fairfield. Rocky Bar, north of Featherville, and Mayfield, northwest of Mountain Home, are ghost 

towns. The main paved access to the area is from U.S. Highway 

20, which goes from Mountain Home across the Camas Prairie. 

Geology

Granitic rocks of the Idaho batholith underlie most of the 

western half of the Hailey 1°×2° quadrangle north of the Snake 

River Plain (fig. 2) (Bennett and others, 1989). The Idaho 

batholith is divided into two lobes, the Atlanta lobe to the south 

and the Bitterroot lobe to the north (Armstrong and others, 

1977). Granitic rocks in this area are mostly Cretaceous in age 

and are part of the south end of the Atlanta lobe. 

In places, the batholith contains roof pendants and xenoliths of metamorphic rocks of uncertain age. The Cretaceous 

batholith is intruded by Tertiary plutons and associated dike 

swarms. Several small exposures of the Eocene Challis Volcanic Group are present near Anderson Ranch Reservoir. Lacustrine sediments of probable Miocene age locally overlie these 

volcanic rocks. The southern end of the batholith is covered by 

the Miocene Idavada Volcanics and by Quaternary sediments 

and basalts of the Snake River Plain. Quaternary gravels and 

alluvium are the youngest sedimentary units in the area.

Major Rock Units

Metamorphic Rocks

Metamorphic rocks of uncertain age are present as roof 

pendants and xenoliths in the batholith. Major exposures 

include the following: House Mountain; Chimney Peak; Lime 
2 Geology and Mineral Deposits of Part of the Western Half of the Hailey 1°×2° Quadrangle, Idaho

0 2 4 MILES

0 2 4 KILOMETERS

FOOTHILLS

ROAD

Boardman Cr

Mountain Home

Dixie

Mayfield

Prairie

Twin Springs

Rocky Bar

Atlanta

Featherville

Hill City

Fairfield

Idaho

City

Pine

Bennett Mountain

Cathedral

Rocks

Arrowrock Dam

Anderson Ranch Dam

Windy Gap

Smith Prairie

Moores Flat

Camas Prairie

Danskin

Bridge

Bennett

Creek

Basin

Iron Mtn

Bald Mtn

Gunsight Pk

Cayuse Pt

Rose Pk

Steel Mtn

Three Point Mtn

Boise

Blakes Creek Road

Thomson Ranch

Dog Creek

Campground

Big Smoky

Guard Sta

Trinity Mtn

Smoky Dome

House Mtn

Wood Creek Mtn

Chimney Peak

Danskin

Peak

Lime Cr

Willow Cr

Fall Cr

Bowns Cr

Mannencke Cr

Cow Cr

Ear Cr

Sheep Cr

Mormon Reservoir

Grimes Cr

Mores Cr

Roaring River

Hot Cr

Bear Cr

Elk Cr

South Fork Boise River

South Fork Boise River

Middle Fork Boise River

Middle Fork Boise River

Feather R

Willow Cr

44°

43°

116°

20

84

Creek; numerous small pendants and xenoliths along the 

ridges east of Anderson Ranch Reservoir; exposures along the 

dirt road between Pine to Dixie Gulch Hot Springs on the east 

side of the South Fork of the Boise River; and Wood Creek 

Mountain.

Metamorphic rocks at House Mountain include biotite 

quartzite, diopside-calc-silicate gneiss, and diopside-graphite 

marble (Jacob, 1985). At Chimney Peak, the rocks are calcsilicate gneiss and quartzite. The correlation of metamorphic 

rocks in the study area with other metasedimentary rocks in 

Idaho is unknown. The rocks are probably equivalent to Paleozoic rocks farther to the east or to Precambrian rocks at the north 

end of the Sawtooth Range near Stanley, Idaho (Fisher and others, 1983). The metamorphic rocks obviously represent the roof 

of the batholith. Most are associated with aplite and pegmatite 

that are at the top of the batholith and intrude the roof rocks.

Figure 1. Location map showing the western half of the Hailey 1°×2° quadrangle, Idaho.
3

Rocks of the Idaho Batholith

The Idaho batholith is composed of several units of Cretaceous age (Kiilsgaard and Lewis, 1985; Lewis and others, 

1987). In the Atlanta lobe, tonalite is intruded by biotite granodiorite that grades into two-mica granite. A late stage of the 

two-mica granite, leucogranite, is present as numerous dikes and 

small plutons. Leucogranite is rare in the western part of the 

Hailey 1°×2° quadrangle. In addition to the above common rock 

types, a large area between House Mountain and Smoky Dome 

contains an unusual abundance of pegmatite and aplite dikes, as 

compared with most of the Atlanta lobe. 

Isotopic dates for batholith rocks are summarized in Lewis 

and others (1987). The tonalite is believed to have formed about 

95-85 Ma. The granodiorite exhibits a complex cooling history 

(Lund and others, 1986) but probably formed between 85 and 75 

Ma. The two-mica granite is 80-70 Ma, based on concordant 

dating of muscovite-biotite pairs by both conventional K/Ar and 

Ar39/40 techniques. Leucogranite plugs and dikes are about 70–

75 Ma based on K/Ar, and Ar39/40 dates.

Tonalite bodies that form the western border zone of the 

batholith are near the 0.704/0.706 strontium isopleth that marks 

the boundary between continental crust to the east and accreted 

terranes to the west (Armstrong and others, 1977; Fleck and 

Criss, 1985; Criss and Fleck, 1987). Tonalite is also present 

along the eastern side of the batholith (Fisher and others, 1983). 

Hornblende tonalite is present along the South Fork of the 

Boise River between Little Jumbo Creek and Boardman Creek. 

It weathers to sharp pinnacles and the canyon of the South Fork 

narrows considerably. Numerous rapids and the steep topography in this part of the canyon are distinctive and picturesque. 

Unfortunately, contact relationships between the tonalite and the 

surrounding granodiorite are not exposed. Two K/Ar dates 

(hornblende) of 104 and 96 Ma are similar to other tonalite ages; 

however, these ages may be due to excess argon in the hornblende. The tonalite is similar in appearance to tonalite in the 

Loon Creek area on the Challis 1°×2° quadrangle to the north of 

the study area (Fisher and others, 1983).

Along the western border zone of the Idaho batholith in the 

Challis quadrangle, the tonalite is intruded by massive biotite 

granodiorite, the main phase of the batholith. A broad band of 

this granodiorite extends northeast-southwest across the Hailey 

quadrangle from the Snake River Plain to the Sawtooth Valley 

(fig. 3). Another large mass is between the Sheep Creek 

batholith (Eocene) on the Middle Fork of the Boise River and 

the Tertiary complex near Idaho City (fig. 2). 

The biotite granodiorite is gradational into two-mica granite that is present only in the western part of the study area. The 

two-mica granite occasionally contains small red garnets. 

Highly weathered exposures of two-mica granite occur along 

and around Indian Creek north of Mayfield. Another wellexposed outcrop was mapped at the mouth of Pole Creek, just 

west of Fiddler Flat. There are no known exposures of two-mica 

granite east of Danskin Peak Lookout; however, there are exposures of the granite north of the Middle Fork of the Boise River 

(Kiilsgaard and others, in press).

The area between House Mountain and Smoky Dome, 

including most of Anderson Ranch Reservoir, contains primarily 

biotite granodiorite that is intruded by large numbers (greater 

than 50 percent of the rock) of pegmatite and aplite dikes. The 

striped appearance of the ridges extending east from House 

Mountain Lookout to the reservoir (north of Evans Creek) that 

are visible from the top of the Anderson Ranch Dam grade is 

due to plants growing differentially along aplite and pegmatite 

dikes and on granodiorite (fig. 4). In some places around the 

reservoir, for example on the Anderson Ranch Dam grade, there 

are so many dikes that the host granodiorite looks like totally 

engulfed, ellipsoidal xenoliths.

This amount of aplite and pegmatite is unusual in the 

southern part of the Atlanta lobe and is the highest concentration 

noted to date in the Challis and Hailey quadrangles. The roof of 

the batholith near Elk City in the Elk City 1°×2° quadrangle to 

the north also contains a high concentration of pegmatite and 

aplite (Lewis and others, 1990). The pegmatite and aplite are 

assumed to be Cretaceous in age because no similar younger or 

older rocks have been described. 

Tertiary Intrusive Rocks

A number of Tertiary (Eocene) intrusions are shown in 

figure 2. Plutonic rocks include a bimodal suite of quartz 

monzodiorite and granite (Bennett and Knowles, 1985; Lewis 

and Kiilsgaard, 1991). As elsewhere in the region, distinctive 

Tertiary epizonal pink granite is commonly spatially associated 

with rocks of the quartz monzodiorite suite.

Major granitic bodies of Tertiary age include Smoky 

Dome, the Sheep Creek batholith (formerly the Twin Springs 

pluton but renamed by Lewis and Kiilsgaard, 1991), small plutons south of the Camas Prairie near the Blackstone mine 

(DeLong, 1986), the granodiorite at Cat Creek (fig. 5), and granitic rocks near Hill City and Mormon Reservoir. These A-type 

or anorogenic granites (Collins and others, 1982), are generally 

more radiogenic than either the Cretaceous rocks or the quartz 

monzodiorite suite, appear as anomalies on airborne radioactivity surveys, and range in age from 45–40 Ma (Bennett and 

Knowles, 1985). 

Large masses of rock of the quartz monzodiorite suite 

(including granodiorite, tonalite, and gabbro) are west of the 

Sheep Creek batholith, south of the Sheep Creek batholith in the 

Trinity Peaks, surrounding Smoky Dome on the north, south, 

and east (Iron Mountain, fig. 6), and at the mouth and along the 

lower stretch of Lime Creek. The quartz monzodiorite suite 

generally contains hornblende and complexly zoned plagioclase 

and magnetite and commonly xenoliths or restites that distinguish these rocks from Cretaceous granitic rocks. These rocks 

range in age from 55–45 Ma (Johnson and others, 1988; Lewis 

and Kiilsgaard, 1991).

A number of gabbroic plugs and dikes are present in the 

Ear Creek area. Several of these were intruded along the 

Moores Flat fault. A few gabbroic dikes similar to the Ear Creek 

rocks are present just south and west of Trinity Mountain Lookout, and poor exposures were noted south of Bennett Creek 

basin (about 1.5 mi southwest of Dixie Summit). Gabbro has 

not been observed elsewhere in the Atlanta lobe. The gabbroic 

rocks are assigned a speculative Tertiary age, based on intrusive 

Geology
4 Geology and Mineral Deposits of Part of the Western Half of the Hailey 1° 2° Quadrangle, Idaho

relationships. Some of the exposures of the monzodiorite at

Lime Creek look very similar in outcrop to the gabbroic rocks.

As elsewhere in the Atlanta lobe, dike swarms of Eocene

age are common in the western half of the Hailey

quadrangle. Most of these dikes are related to the bimodal

Tertiary plutonic suite noted above and are described in Bennett and Knowles (1985). The dikes are mapped as rhyolite

(pink granite related) or rhyodacite dacite (quartz monzodiorite related).

Rhyolite dikes in the western half of the Hailey 1°×2°

quadrangle are relatively rare as compared to the swarms of

0 10 20 MILES

0 10 20 KILOMETERS

Kg

Kg

Kg

Kg

Kg

Kg

Kg

Kg

Kgd

Kgd

Kgd

Kgd

Kgd

Kgd

Kgd

Kgd

Kgd

Kgd

Kgd

Kgd

Kgd

Kgd

Kgd

Kgd

Kgd

Kgd

Tqm

Tqm

Tqm

Tqm

Qbb

Qbb

Qbb

Qf

Tcv

Tcv Tbb

Tbb

Q

Td

Tv Tv

Tv

Tv

_\

Tg

Tg

Tcv

Tg

Tg

Tg

Tg

Tg

Tg

Kt

Kt

Kap

Kap

Kap

Kap

Qsp

Kap

Kgd

Kgd

Anderson

Ranch

Res

Steel Mtn

Fairfield

Mountain Home

Idaho City Atlanta

Smoky

Dome

Chimney Peak

Smith Prairie

Western Snake River Plain

Extension of the Boise Front fault

Camas Prairie

Sheep Creek Batholith

Sawtooth

Batholith

Trans Challis fault system

Deer Park Fault

Montezuma Fault

Willow Cr Bear Cr fault

Cayuse Creek

dike swarm

E Willow Creek

fault

Trinity flt

West Willow Creek fault

North

Fork

Deep

Cr fault

Iron Mountain

segment

Moores Flat fault

Cow Creek

fault

Trinity Mtn

p

44°

43°

43°30'

116° 115°

Figure 2 (above and facing page). Generalized geologic map of the western half of the Hailey 1° 2° quadrangle, Idaho.

Dike Swarms

×

×

1°×2°
5

Quaternary rocks and deposits

Basalt, undivided (Pleistocene)

Alluvial fans and gravels

Smith Prairie Basalt (Pleistocene)

Undivided Quaternary deposits and other rocks

Tertiary rocks

Basalt, undivided (Miocene)

Idavada Volcanics (Miocene)

Challis Volcanic Group (Eocene)

Quartz monzodiorite

Granite (pink)

Diorite

Cretaceous rocks

Biotite granodiorite

Muscovite-biotite granite

Tonalite

Aplite/pegmatite complex

Paleozoic(?) and Precambrian(?) rocks

Metasedimentary rocks and roof pendants (age uncertain)

Qbb

Qf

Qsp

Q

Tbb

Tv

Tcv

Tqm

Tg

Td

Kgd

Kg

Kt

Kap

p

EXPLANATION FOR FIGURE 2 rhyolite dikes mapped in the Challis 1°×2° quadrangle. Swarms 

of dikes are present near Three Point Mountain, a swarm 

extends from Negro Creek to northeast of Chimney Peak, and a 

small dike or plug is present west of the townsite of Dixie. The 

numerous dikes just west of Smoky Dome are more of a pink 

granophyre than rhyolite and are unusually abundant. 

A major rhyodacite and dacite dike swarm hosted by Cretaceous granodiorite, the Cayuse Creek dike swarm (fig. 2) is 

present northeast of the granodiorite at Trinity Mountain. 

Numerous dikes in this swarm are exposed along the road from 

Featherville to Rocky Bar, along the Lincoln Creek road, and 

along Little Cayuse Creek (Slavik, 1987). To the north, the 

swarm ends abruptly at the divide between Lincoln Creek and 

Red Warrior Creek. The swarm strikes northeast, paralleling the 

Willow Creek-Bear Creek fault. Both Gunsight and Ross Peaks 

are outcrops of large dikes. The number of dikes increases to 

the east as basin and range faults are crossed. A few dikes are 

present west of the Iron Mountain segment of the Deer Park 

fault, more dikes are present between this segment and the Montezuma fault, and a great many more dikes are present east of the 

Montezuma fault, along the north-south segment of the South 

Fork of the Boise River north of the Big Smoky Guard Station 

(fig. 2) (Good, 1986).

Excellent examples of dike-pluton relationships were noted 

where basin and range faults have preserved older batholith 

rocks and Tertiary dikes on the downthrown side of the faults 

and exposed the corresponding parent plutons of the Tertiary 

dikes on the upthrown side. The granophyre-rhyolite dike 

swarm just west of the pink granite that forms Smoky Dome 

(separated by the Iron Mountain fault segment of the Deer Park 

Geology

Figure 3. Typical biotite granodiorite terrane in the Mayfield Peak 7.5-minute quadrangle, Idaho. View looking south across 

Willow Creek from near the head of Fornham Creek.
6 Geology and Mineral Deposits of Part of the Western Half of the Hailey 1°×2° Quadrangle, Idaho

Figure 5. Cat Creek summit, Idaho, looking north toward Wood Creek Mountain. Granodiorite at Cat Creek is in foreground. 

Wood Creek Mountain consists of aplite and pegmatite dikes in biotite granodiorite; small remnants of metamorphic pendants are 

preserved at higher elevations. A northeast-trending fault separates the two areas. 

Figure 4. Ridge north of Evans Creek, Anderson Ranch Reservoir area, Idaho. Vegetation patterns are controlled by pegmatite 

dikes in granodiorite just east of House Mountain Lookout. 
7

fault, fig. 7) is a good example. The alignment of the Little 

Cayuse Creek dike swarm and the Trinity Mountain granodiorite 

also indicates a dike-pluton relationship.

In addition to the bimodal suite described above, finegrained andesite(?) dikes are present in the study area. These 

dikes increase in number toward the Snake River Plain and 

commonly are oriented northwest, parallel with the trend of 

basin and range faults. The dikes are believed to be related to 

basalts of the Snake River Group or the Idavada Volcanics, but 

they could also belong to the lower part of the Eocene Challis 

Volcanic Group.

Challis Volcanic Group

Rocks of the Eocene Challis Volcanic Group are present in 

the vicinity of Anderson Ranch Reservoir (just west of the Lime 

Creek road) and just south of Windy Gap on U.S. Highway 20. 

These rocks are part of the lower, older andesite suite that is the 

most widespread part of the Challis volcanic field. Most of the 

andesite flows are thought to be from local vents rather than 

from large calderas, unlike the younger ash flows in the Challis 

Volcanic Group. An excellent description of the Challis Volcanic Group in the region is given in Moye and others (1988). 

Intercalated with the andesite units are fine-grained sedimentary rocks that may be lake- bed deposits similar to, but 

more indurated than overlying Miocene(?) age lacustrine deposits. Apparently, this part of the South Fork of the Boise River 

(now Anderson Ranch Reservoir) contained several large lakes 

intermittently during the past 45 million years. Perhaps Eocene 

volcanic activity dammed ancestral drainages, resulting in formation of the lakes in a manner similar to the manmade dam that 

today controls the reservoir. 

Idavada Volcanics

The southern part of the Atlanta lobe is covered in places 

by rhyolite of the Miocene Idavada Volcanics. In the Hailey 

1°×2° quadrangle, Idavada rocks are preserved in a triangularshaped wedge north of the intersection of the eastern and western Snake River Plains. The Camas Prairie (Cluer and Cluer, 

1986) is a crude northern boundary of the Idavada exposures. 

No attempt was made to subdivide the Idavada in this study; 

however, Wood (1989) and Wood and Gardner (1984) described 

the Idavada units on Bennett Mountain and at Danskin Peak. 

They noted two sequences of densely welded ash-flow tuff: the 

older rhyolites of Bennett Mountain and the younger rhyolites of 

the Danskin Mountains. These sequences are separated by a 

major fault that forms the west scarp of Bennett Mountain. 

Combined thickness of the two sequences is estimated at more 

than 3,280 ft. 

These tuffs are similar to tuffs in the southwestern part of 

the Snake River Plain (Owyhee County) described by Ekren and 

others (1984) and Bonnichsen and others (1989). Little or no 

pyroclastic fabric is preserved in these rocks, and the rocks must 

Geology

Figure 6. Tertiary monzodiorite containing inclusions (enclaves) near the Iron Mountain Lookout. Pen shown for scale.
8 Geology and Mineral Deposits of Part of the Western Half of the Hailey 1°×2° Quadrangle, Idaho

have been very hot when extruded. Some of the Idavada rocks in 

Owyhee County may have been giant rhyolite lava flows (Bonnichson and Kauffman, 1987). All authors agree that these are 

unusual rhyolites, and their genesis is still not fully understood. 

The age of the Danskin Peak-Bennett Mountain flows is not 

known, but, based on the assumed age progression of the Yellowstone hot spot (Leeman, 1989), they probably formed about 

10–8 Ma.

A series of basin and range faults (an older set trending 

north-northwest and a younger set trending northwest) cuts the 

Idavada Volcanics and Bennett Mountain. These faults have 

tilted blocks of the Idavada to the northeast. Numerous cold 

springs mark the location of these faults and are quite striking in 

their map pattern. The west and east forks of Long Tom Creek, 

Pony Creek, and Willowdale Creek-Pole Creek follow three of 

these structures. 

West of the last exposure of rhyolite at Danskin Peak, several very thick and persistent dikes are present that, in hand specimen, bear a striking similarity to Idavada ash flows. A few of 

these are exposed along the Blacks Creek road between the 

Snake River Plain and the divide between Blacks Creek and 

Wood Creek near Three Point Mountain. The great length of 

these dikes is clear from exposures of one of the Blacks Creek 

dikes that is visible about 2 mi east of the junction of the Blacks 

Creek-Foot Hills roads on the Foot Hills road. The best exposure of one of these dikes is on private land, about 1 mi north of 

the Thomson Ranch on Bowns Creek. These dikes strike northnorthwest, are very thick (as much as 100 ft), and have pronounced horizontal joints (fig. 8). One of the exposures at 

Thomson Ranch is a black vitrophyre that has very large (as 

much as 20 mm) sanidine phenocrysts. A whole-rock chemical 

analysis of a sample collected by Thor Kiilsgaard shows 63 percent SiO2 and 17 percent Al2O3. This analysis is significantly 

different from a typical analysis of Idavada rhyolite, which 

shows more than 70 percent SiO2 and less than 14 percent 

Al2O3 and indicates that the dikes are not related to Idavada 

lavas. These dikes do not resemble any of the Eocene or other 

dikes that have been observed in the Challis and Hailey studies. 

These would be the first dikes described in the Idavada, if they 

belong to this unit.

Lacustrine Deposits

In the Anderson Ranch Reservoir area a sequence of 

Miocene(?) lacustrine deposits overlie the Challis Volcanics. 

These deposits are widespread in Idaho (T.H. Kiilsgaard, oral 

commun., 1990) and are equivalent to the Latah Formation in 

northern Idaho and to the Payette Formation north and west of 

Boise. The beds range from fine-grained silt and clay to 

gravel;some contain pieces of plant fossils.

Figure 7. Looking northwest from just west of Smoky Dome, Idaho. Steel Peak is to the far left in the background. Higher peaks in 

middle and right background are on the east side of the Iron Mountain segment of the Deer Park fault. The rock east of the fault is 

granodiorite and some dikes. The center of the photograph is the downdropped western side of the fault; the rock is also mostly 

granodiorite. Light-colored rocks in the right corner are aplite and pegmatite dikes (part of the swarm just west of Smoky Dome).
9

Basalts and Gravel Deposits

In the South Fork of the Boise River Canyon and Anderson 

Ranch Reservoir area there are many exposures of flat-lying 

basalts, a number of which form rimrock along the river and 

above the reservoir. Howard and Shervais (1973) and Howard 

and others (1982) described the basaltic volcanic rocks of the 

Smith Prairie area in detail. Ten flows were recognized at Smith 

Prairie, Anderson Ranch Reservoir, and along the South Fork of 

the Boise River. The plateau at Smiths Prairie is formed of flows 

of the Steamboat Rock Basalt that erupted from a vent located 2 

mi south of the town of Prairie and flowed 37 mi down the South 

Fork to the Snake River Plain. The Steamboat Rock Basalt is 

dated at about 1.8 Ma by K-Ar methods and correlates with 

Pliocene and Pleistocene rocks of the Idaho Group (Malde and 

others, 1963). The basalt flows dammed the South Fork of the 

Boise River, and gravels were deposited on and behind the dam. 

Subsequently, a vent on the hillside above Smith Creek erupted 

the basalt of Smith Creek and then several smaller flows. Next, 

the Smith Prairie Basalt (about 0.2 Ma by K-Ar methods) and 

correlative in part with the Pleistocene and Holocene Snake 

River Group of Malde and others (1963) was erupted from vents 

on Dry Buck Creek. By this time, the South Fork had eroded 

deeply through earlier flows that had filled the canyon. Flows of 

the Smith Prairie Basalt went down Black Canyon and refilled 

500 ft of the South Fork Canyon and once again dammed the 

river. Some of these flows reached the present site of Arrowrock 

Dam. Gravel was deposited on the Smith Creek basalt dam, and 

remnants of these gravels are preserved along the river. 

Subsequent erosion has lowered the river course through both 

lava dams leaving remnants of the Prairie Basalt basalt that are 

now locally called the “Lower Bench” (fig. 9). The narrow canyon and associated rapids, so beloved by Boise rafters and drift 

boaters, are the result of the second canyon filling and erosion. 

Pillow basalts mark where basalts flowed into the river. An 

excellent example of pillow basalts is along the Anderson Ranch 

Reservoir road where it climbs from Fall Creek to the plateau 

rim above the reservoir on the way to Pine.

One of the most interesting areas in this study is located in 

upper Mennecke Creek west of the Danskin Bridge. Here 

numerous landslides and small slumps are developed in a thick 

sequence of gravels (fig. 10). There are at least two gravel units: 

a younger unit composed of loose gravel and an older indurated 

gravel. The older gravel is tilted about 45° to the east (fig. 11). 

The flat-lying younger unconsolidated gravel overlies the older 

indurated unit and, in places, flat-lying basalts overlie both 

deposits (fig. 12). The two gravel units may be related to the 

basaltic volcanism as described by Howard and Shervais (1973). 

The older gravel may have been deposited when the river was 

dammed by the Steamboat Rock Basalt and the younger gravel 

was deposited when the river was dammed by the Smith Prairie 

Basalt. The unconformity may record movement associated 

with the Cow Creek fault, which is exposed in Mennecke Creek 

(fig. 13). If this interpretation is correct, then the Cow Creek 

fault was reactivated between the eruption of the basalts, sometime between the Pliocene-Pleistocene and the Holocene. As 

noted earlier, basalt dikes in the Cow Creek fault are sheared and 

shattered, also implying relatively recent movement. Both 

Geology

Figure 8. Dike of unknown age, Thomson Ranch on Bowns Creek. Mayfield 15-minute quadrangle, Idaho.
10 Geology and Mineral Deposits of Part of the Western Half of the Hailey 1°×2° Quadrangle, Idaho

Figure 9. View into the South Fork of the Boise River near Dawes Creek, Idaho. Older basalt flows of the South Prairie Basalt 

form the high rim on the right side of the photograph, younger flows form the “lower bench.” Granodiorite of the Idaho batholith 

is on the left.

Figure 10. Landslides in gravels of Mennecke Creek west of the Danskin Bridge, Idaho. View looking south; tuffs of the Idavada 

Volcanics form back ridge.
Geology 11

Figure 11. Indurated tilted gravels on east side of Mennecke Creek, Idaho.

Figure 12. Gravels below basalt in Mennecke Creek, Idaho. 
12 Geology and Mineral Deposits of Part of the Western Half of the Hailey 1°×2° Quadrangle, Idaho

gravels obviously predate recent downcutting that has left gravel 

benches preserved above the present river and reservoir level.

Some of the gravel in Mennecke Creek may be older than 

the basalts. At several locations near the contact of the gravels 

with the Idavada Volcanics, it appears that some gravel lies under 

the volcanic rocks. These sediments are probably equivalent to 

the Miocene lacustrine deposits described earlier.

Just west of Mennecke Creek, a red scar is visible where a 

basalt dike cuts gravels. The dike is a feeder for basalt flows 

that cap the gravels in this area. Late Cenozoic basaltic dikes 

are common along the southern edge of the Atlanta lobe and are 

related to young Snake River Plain basaltic volcanism. Many 

such dikes are present in the southern part of Anderson Ranch 

Reservoir area, and they probably fed some of the flows that are 

preserved in the South Fork of the Boise River canyon (called 

the basalt of Anderson Ranch by Howard and others, 1982). 

Some dikes may also have followed basin and range faults, as 

evidenced by Red Mountain (fig. 2), a young basalt cinder cone 

that sits astride the Trinity Mountain fault (fig. 14). The basalt 

of Fall Creek (Howard and others, 1982) flowed from Red 

Mountain down Fall Creek to the South Fork of the Boise River 

(now Anderson Ranch Reservoir). Other examples of basalt 

apparently related to basin and range faulting are small patches 

of columnar basalt near the Iron Mountain fault just west of the 

Iron Mountain Lookout and basalt along the West Willow 

Creek fault.

Alluvial Deposits

All active streams in the study area contain alluvial deposits typical of this part of Idaho. Large quantities of silt and sand 

are being impounded behind Anderson Ranch Dam and may 

someday form a lacustrine deposit.

Structure

The structural history of the western half of the Hailey 

1°×2° quadrangle is relatively complex. Compression and 

extension in the Late Cretaceous and early Tertiary is indicated 

by the regional decollement(s) exposed at House Mountain and 

Chimney Peak. Two major periods of extension, one in the 

Eocene and another related to younger basin and range faulting, 

reactivated some older faults and formed new structures. The 

faulting has dissected the area into a series of complex rhomboid-shaped blocks that have all moved relative to each other.

Figure 13. Cow Creek fault (far right), older gravels (center), and younger gravels (left) in Mennecke Creek, Idaho. Smith Prairie Basalt

forms flat plain on both sides of the South Fork of the Boise River. Smith Prairie is in the center of the photograph and House Mountain 

is to the right in the background.
13

Cretaceous-Tertiary(?) Compression and Extension(?)

Below the other metamorphic rocks on House Mountain is

orthogneiss that I believe formed either as part of a CretaceousEocene decollement related to extension or during regional

thrusting. The orthogneiss crops out along the lower part of the

Cow Creek grade and along the road from South Fork to Prairie

road on the hill above Danskin bridge. The protolith for some of

the orthogneiss on Prairie Hill is biotite granodiorite of the

batholith. Just west of the first switchback at the bottom of the

hill is sheared granodiorite and to the west of this exposure are

the Cathedral Rocks, which are made up of undeformed granodiorite that underlies the decollement.

According to the extension hypothesis, the orthogneiss is

part of the decollement of an eroded core complex similar to

core complexes in the Pioneer Mountains east of Hailey and

near Priest Lake in northern Idaho, as well as elsewhere in the

western United States and in British Columbia, Canada (Jacob,

1985). That core complexes in Washington and British Columbia have a ductile component related to Late Cretaceous compression and a more brittle component related to Eocene

extension (Rhodes and Hyndman, 1984). The orthogneiss at

House Mountain may be the ductile component of the core complex and the highly shattered and broken rocks around Anderson

Ranch Reservoir the more brittle component.

According to the regional thrusting hypothesis, the orthogneiss represents a deep-seated decollement to one of a series of

major thrust sheets in eastern Idaho (Skipp, 1987). Laramide

thrusting in Idaho started before intrusion of the batholith and

probably continued through batholith formation, as indicated by

intrusion of several thrust faults by the batholith (Skipp, 1987).

Unloading the batholith by thrusting overlying sedimentary sequences to the east may have reduced lithostatic pressure on the batholith magma chamber and triggered the release

of volatiles represented by the abnormally high concentration

of aplite and pegmatite between House Mountain and Smoky

Dome. Undeformed aplite and pegmatite dikes cut the orthogneiss at House Mountain (fig. 15), but some pegmatite may be

the protolith for the orthogneiss. If the age of all of the aplite

and pegmatite is Cretaceous, then the decollement formed

during the Cretaceous and was intruded by its own aplite and

pegmatite dikes.

Metamorphic rocks in the pendant at Chimney Peak are

underlain by gneissic hornblende granodiorite. The foliation in

the gneissic rocks is so pronounced that outcrops appear like

stacked poker chips or playing cards (fig. 16). Hornblende

forms a strong lineation in the foliation plane that indicates

movement of the Chimney Peak metasedimentary rocks to the

southeast. I believe that the gneissic granodiorite is equivalent

Geology

Figure 14. Basalt lava flow from the Red Mountain vent along Fall Creek, Idaho, north of Fall Creek Lodge.

House Mountain Decollement

Chimney Peak
14 Geology and Mineral Deposits of Part of the Western Half of the Hailey 1°×2° Quadrangle, Idaho

Figure 15. Orthogneiss and sheared biotite granodiorite and aplite and pegmatite dikes that are intruded by undeformed aplite 

and pegmatite dikes. Top of the Prairie grade on the road from Danskin Bridge to Prairie, Idaho.

Figure 16. Sheared poker chip biotite-hornblende granodiorite north of Chimney Peak on Salix Creek, Idaho. 
15

to the orthogneiss at House Mountain and is part of the regional

decollement in this area. Pegmatite and aplite surrounding

Chimney Peak are foliated (Worl and others, 1991) and in

places, nonfoliated pegmatites intrude these foliated rocks.

Orthogneiss that has a protolith of granodiorite and aplite

and pegmatite is present about 1 mi south of the intersection of

the Pine to Dixie Gulch Hot Springs road on the east side of the

South Fork of the Boise River. The first gneissic outcrops going

south from the hot springs are where the road comes very close

to the South Fork (fig. 17). As on Prairie Hill, the orthogneiss is

cut by undeformed Cretaceous age aplite and pegmatite dikes

and younger Tertiary dacite and rhyolite dikes. Foliated granodiorite is exposed in a small hill just before the Dog Creek

campground on the Pine to Dixie Gulch road on the west side of

the river. At the southern intersection of the roads that traverse

the east and west sides of the river from Pine to Dixie Gulch,

just east of Pine, are outcrops and float from metamorphic rocks

that form small pendants and xenoliths all along the ridge east of

the South Fork and the reservoir, from Pine to Lime Creek. The

metamorphic rocks at Lime Creek were not subdivided during

this study, but there is orthogneiss in the sequence. All of these

exposures may be related to the House Mountain decollement.

A number of exposures at the top of the Cow Creek grade

show features that are typical of major faults in the Idaho

batholith (fig. 18). Granodiorite and pegmatite have been

ground to a white powder, and remnants of granodiorite are

present in the gouge. Basalt dikes of probable Pliocene-Pleistocene age cut the fault but are in turn sheared and shattered.

The Cow Creek fault is believed to be relatively flat. Exposures

similar to those on the Cow Creek grade are present in Mennecke Creek about 2 mi west of Cow Creek (fig. 19). The Cow

Creek fault was probably active during basin and range extension because it is similar to exposures of the Deer Park fault at

Big Elk Creek (fig. 22). The Cow Creek fault is, however, much

flatter than the typical basin and range fault and may be a more

complex structure related to the House Mountain decollement

that was later deformed during basin and range extension. The

Cow Creek-House Mountain decollement separates aplite and

pegmatite and included metasedimentary rocks east of Prairie

from monotonous granodiorite and two-mica granite of the

batholith to the west.

DeLong (1986) described three types of mylonite in

batholith rocks near Halls Gulch, south of the Camas Prairie.

He believed that formation of the mylonite was related to the

intrusion of the batholith.

Geology

Figure 17. Orthogneiss and sheared biotite granodiorite on the old Pine to Dixie Gulch Hot Springs road, Idaho.

Old Pine-Dixie Gulch Hot Springs Road Orthogneiss

Mylonite near Hall Gulch

Cow Creek Fault
16 Geology and Mineral Deposits of Part of the Western Half of the Hailey 1°×2° Quadrangle, Idaho

Figure 18. Cow Creek fault near the top of the Cow Creek grade. Light-colored exposures are biotite granodiorite gouge. Dark 

bands (left side of photograph) are sheared basalt dikes.

Figure 19. Outcrop between Mennecke Creek and Cayuse Creek, Idaho. The fault gouge in biotite granodiorite is interpreted as 

being part of the Cow Creek fault (see fig. 13).
17

Thrusting and the Batholith

In Idaho and western Montana, a pie-shaped wedge of continental crust lies between two major linear features, the Lewis

and Clark line to the north and the eastern Snake River Plain to

the south; the strontium isopleth in western Idaho marks the

western edge of old continental crust. This wedge of continental

crust includes the Helena salient in the overthrust belt in Montana and the major thrust sheets in eastern Idaho.

A possible explanation forthe salient is asfollows:Collision

of the accreted terranes in western Idaho moved the thrust plates

that are now in eastern Idaho and western Montana eastward. The

Lewis and Clark line and the Snake River Plain, old continental

plate boundaries, were reactivated and accommodated this compression by left-lateral movement on the Lewis and Clark and

right-lateral movement in the eastern plain. This thrusting was

maximum in the pie-shaped wedge. As thrusting continued,

thrust sheets stacked up and thickened the continental crust

between the Lewis and Clark line and the eastern Snake River

Plain. When subduction resumed following accretion, the greatly

overthickened continental crust contributed large volumes of

granitic magmas that eventually formed the Idaho batholith. A

similar scenario has been suggested by Skipp (1987).

Eocene Extension

The effects of a major extensional event during the Eocene

that affected Idaho from the Snake River Plain northwest into

central British Columbia is well documented (Ewing, 1980;

Bennett, 1986). Bennett (1986) noted that Eocene extension in

Idaho is confined to a crustal block bordered on the south by the

eastern Snake River Plain and on the north by the Lewis and

Clark line. He noted that both features could be much older than

Eocene and may represent platelet boundaries in the North

American plate. Extensional stress oriented northwest-southeast generated or reactivated northeast-trending faults. Best

known of these northeast-trending structures is the Trans-Challis

fault system, that extends across Idaho from Idaho City to Gibbonsville and into the alkaline province in Montana (Kiilsgaard

and others, 1986). In Montana, this structure is known as the

Great Falls lineament (O’Neill and Lopez, 1985). Along the

Trans-Challis fault system are numerous Tertiary rhyolite dike

swarms and granitic plutons. A significant number of gold

mines and prospects also are along this structure, including the

important mines at Boise Basin and the newly discovered

Beartrack deposit, the largest gold discovery in the State’s history. Major mines at Atlanta, Rocky Bar, and the Neal district

are along other northeast-trending shear zones. The age of the

deposits at Atlanta (69.1 Ma and 68.1 Ma on vein muscovite,

Snee and Kunk, 1989) and at Rocky Bar (58–57 Ma on vein

muscovite; Snee and Kunk, 1989) strongly suggest that there

was earlier movement (Cretaceous-Paleocene) on some of the

northeast structures that were reactivated in the Eocene. Most of

these districts are being explored today for heap-leach, bulkminable, low-grade gold deposits. The eastern Snake River

Plain may be another locus of Eocene extension, and the Pioneer

core complex (Wust and Link, 1988) and House Mountain

decollement (Jacobs, 1985a) may also be products of this

extension. In the western part of the Hailey quadrangle,

northeast-trending faults have been crosscut and dissected by

younger basin and range faults; however, radar imagery (fig. 20)

clearly shows the strong northeast structural grain.

Major northeast-trending faults in the western part of the

Hailey quadrangle include the Willow Creek-Bear Creek fault,

the Moores Flat fault, the Middle Fork of the Boise River fault,

the Trans-Challis fault system near Idaho City, the North Fork of

Deep Creek-Yellow Pine Creek fault, and a fault that separates

House Mountain from a hummocky area to the north along the

Deer Creek-Meadow Creek road. Note that there are three

Willow Creek faults: the northeast-trending Willow Creek-Bear

Creek fault; a northwest-trending basin and range fault along the

Willow Creek in the center of the Hailey quadrangle (East

Willow Creek fault, an extension of the Montezuma fault); and

another northwest-trending basin and range fault along the

Willow Creek that crosses the Blacks Creek road southwest of

Prairie (referred to herein as the West Willow Creek fault).

Another possible northeast-trending fault is along the upper

reaches of Lime Creek.

The Willow Creek-Bear Creek fault has a hot spring at its

southwestern end and is the locus of several mineral deposits on

Bear Creek including the Red Horse and El Oro mines. Granodiorite exposures just east of Shake Creek Ranger Station along

the South Fork road are strongly foliated and may be where the

Willow Creek-Owl Creek fault crosses the road. The Moores

Flat fault probably controlled the emplacement of several

Tertiary intrusions. It may also explain why the forks of Lime

Creek flow from north to south and then turn west, parallel with

the strike of the fault, and why the drainages south of the fault

all flow southward. The Moores Flat fault is also on the projection of the Dillon lineament and may be the structure that forms

the scarp on the west end of Bennett Mountain. The Middle

Fork fault is aligned with the northeast-trending southern

boundary of the Sawtooth Range, which may be fault controlled

(Kiilsgaard and others, 1970). Other smaller unnamed northeast

fault segments are shown on the geologic map of the Hailey

1°×2° quadrangle (Worl and others, 1991).

Eocene dikes and plugs were intruded along northeasttrending structures such as the Trans-Challis fault system. The

location of the gabbro plug and other Tertiary intrusions along

the Moores Flat fault indicates a similar relationship. This relationship does not mean that these northeast structures formed in

the Eocene, only that major movement occurred during the

Eocene. Several of these northeast structures are older than

Tertiary, as proven by the aforementioned Cretaceous-Paleocene

mineralized rock along some of these faults. The Trans-Challis

fault system and eastern Snake River Plain may represent even

older major intracontinental fractures.

The pronounced northeast structural grain in the Hailey

quadrangle can be described as a series of four

Geology

Eocene and Older, Normal Northeast-Trending Faults

Regional Northeast Structures and Trends

1°×2°

1°×2°
18 Geology and Mineral Deposits of Part of the Western Half of the Hailey 1°×2° Quadrangle, Idaho Boise Front Fault West Willow Creek Fault Trinity Fault Iron Mt. segment Deer Park Fault Montezuma FaultATLANTA ROCKY BAR Figure 20. Radar image of the Hailey 1°

×2° quadrangle, Idaho.
19

northeast-trending belts characterized by different rock types.

The four belts from south to north are the eastern Snake River

Plain, an extension of the Dillon Cutoff, the Twin SpringsSawtooth lineament, and the Trans-Challis fault system.

The eastern Snake River Plain is the southern limit of

Eocene extension. It is interpreted as the trace of the passage of

the Yellowstone hot spot (Miocene to present), the driving force

for at least part of present-day seismic activity in the basin and

range province in this part of Idaho and Montana. The eastern

Snake River Plain is separated from the next Eocene belt to the

north by younger Idavada Volcanics, basalts, and sedimentary

rocks.

The next Tertiary belt to the north is broad and contains a

number of Tertiary granites including rocks near the Blackstone

mine, outcrops near Hill City, Smoky Dome, and other exposures to the northeast. The pink granite at Mormon Reservoir,

the southernmost exposure of Tertiary granite in the Hailey

quadrangle, and is part of this belt. Farther to the northeast, the belt includes Tertiary granite exposures on Big Smoky

and Prairie Creeks, the Boulder batholith north of Ketchum, and

small Tertiary stocks at Glassford and Ryan Peaks (Fisher and

others, 1983). The granite in Copper Basin, and the Mackay

stock (Idaho Falls quadrangle), and perhaps the Pioneer

core complex may be part of this system. The belt coincides

with the southwest extension of a lineament first referred to by

Ruppel (1982) near Horse Prairie in Montana. This lineament

was recently studied by O’Neill and others (1990), who named

it the Dillon cutoff. In Montana, the Dillon cutoff marks the

contact between thin-skinned thrust sheets in the frontal fold and

thrust belt and block-uplifted older basement rocks to the east in

the Lima recess. Ruppel (1982) noted that the Dillon cutoff in

the Dubois quadrangle in Idaho is a broadly defined zone

that roughly separates Paleozoic rocks south of the lineament

from Precambrian rocks to the north in the Beaverhead and

Lemhi Ranges. The Dillon cutoff also forms the drainage

divides between major streams and rivers in east Idaho including

the Lemhi River-Birch Creek, Pahsimeroi-Little Lost River, Big

Lost River-Warm Springs Creek (Salmon River), and Big Wood

River-Salmon River divides. O’Neill and others (1990) suggested that the Dillon cutoff coincides with the Great Falls tectonic zone. They stated “the Great Falls tectonic zone

apparently first formed as a Proterozoic linear orogen that now

marks the northwest margin of the Wyoming Archean province.”

North of the Dillon cutoff in the study area, a northeasttrending belt, defined by the Sheep Creek-Trinity Tertiary complex and the Sawtooth batholith, is referred to as the Twin

Springs-Sawtooth lineament in this paper. The Twin SpringsSawtooth lineament is separated from the Dillon cutoff by a

wide band of granodiorite that extends across the Hailey quadrangle from Mayfield to the Sawtooth Valley. The Twin SpringsSawtooth lineament is shorter than the Dillon cutoff or the

Trans-Challis fault system and appears to end at the Sawtooth

Valley. The gap between the Sawtooth batholith and the Sheep

Creek batholith in the Twin Springs-Sawtooth lineament is a

basin and range graben formed between the Montezuma and

Deer Park faults (fig. 2). The graben contains Cretaceous

batholith rocks and younger dike swarms. It also contains the

ore deposits at Atlanta Hill, one of the most productive mining

areas in this part of the Hailey quadrangle.

The fourth northeast belt is the Trans-Challis fault system

in the Idaho City area; it is separated from the Twin SpringsSawtooth lineament by a band of granodiorite and two-mica

granite. The Trans-Challis fault system, as noted previously,

extends all the way across Idaho and into Montana where it

merges with the Great Falls tectonic zone. It should be noted

that the granodiorite belts between the Tertiary belts contain

numerous Tertiary dikes and therefore probably overlie Tertiary

plutons at depth.

The spacing between the four northeast-trending belts is

too regular to be coincidental. Recent work in the Elk City and

Hamilton quadrangles in north-central Idaho shows that a

similar pattern of belts continues north of the Trans-Challis

fault system. A major northeast-trending band of Tertiary

granite is roughly coincident with the Bargamin fault (Lewis

and others, 1990) in the Elk City quadrangle and a newly

described northeast-trending graben containing Tertiary

intrusive rocks is in the Hamilton quadrangle (R.S.

Lewis, unpub. mapping, 1991).

The number of pegmatite and aplite dikes and the brittle

deformation (fig. 21) in the Anderson Ranch Dam area are striking. A very large, almost flat fault is exposed at the top of the

road that goes down to the dam. Directly above this fault is the

open pit from which fill for the dam was obtained. The material

in the pit looks in places to be highly sheared granodiorite and

pegmatite. The pit and other examples of cataclasis noted in

many exposures of granitic rocks around the reservoir may be

products of Eocene extension. A younger basin and range

extensional event may be superimposed on the Eocene event.

Basin and Range Extension

Regional basin and range extension from the Miocene

through the present is well documented in the study area (Bennett, 1980). This extensional event occurred at about right

angles to the Eocene extension and produced or reactivated

major northwest-trending structures. These structures extend

from eastern Idaho (including the Beaverhead, Lemhi and Lost

River Ranges) ( Ruppel, 1982) across the southern Atlanta lobe

to the most westerly structure, the Boise front fault (northeast

edge of the western Snake River Plain). Faults of this type in the

western part of the Hailey quadrangle area include the

Montezuma fault (includes East Willow Creek fault), the Deer

Park fault (Anderson, 1934) (including the Iron Mountain segment), the Trinity fault, the West Willow Creek fault, and the

extension of the Boise front fault that separates the batholith

from the Snake River Plain. As noted, a small basalt vent is on

the Iron Mountain segment of the Deer Park fault, just west of

the Iron Mountain Lookout, and Red Mountain, a recent basalt

vent, is on the Trinity Mountain fault. Basin and range structures do not show well on the radar imagery, but the graben

between the Deer Park fault and the Trinity fault is visible on

figure 20.

Geology

Brittle Deformation

1°×2°

1°×2°

1°×2°

1°×2°

1°×2°

1°×2°

1°×2°
20 Geology and Mineral Deposits of Part of the Western Half of the Hailey 1° 2° Quadrangle, Idaho

A spectacular cross section of the Deer Park fault is

exposed where the road crosses a small bridge at Elk Creek

about 4 mi north of Rocky Bar up Blake Gulch (fig. 22). From

this location, the lineament associated with the Iron Mountain

segment of the Deer Park fault is obvious, extending off to the

southeast to Iron Mountain and Smoky Dome. Biotite granodiorite is totally sheared for about 100 ft on either side of the Elk

Creek bridge and appears as an unconsolidated bright-white

powder containing fragments of batholith rocks. The trace of the

fault ascends Elk Creek across the east side of Steel Mountain

and then descends Hot Creek (contains hot springs) on the north

side of the mountain (fig. 23). The fault separates Eocene pink

granite on Steel Mountain from Cretaceous biotite granodiorite

northeast of the fault at Bald Mountain. The ridge that parallels

this fault from Bald Mountain to Cayuse Point to Iron Mountain

is mostly biotite granodiorite containing Tertiary dikes.

A number of hot springs along or near some of the Eocene

faults indicates relatively recent movement along these segments, probably in response to basin and range tectonics. As

noted, some of these faults moved during the Cretaceous and

Paleocene. The crosscutting of northeast-trending Eocene (or

older) structures by northwest-trending Miocene or younger

structures has broken the study area into a series of rhomboidshaped blocks that have moved relative to each other in response

to basin and range extension. This rhomboid pattern greatly

complicates the tectonic chronology for this area and makes it

difficult to decipher what type of movement occurred and when

on any of these faults.

This rhomboid pattern is similar to that described for the

shape of the Boulder batholith in Montana (Schmidt and others,

1990). Emplacement of the Boulder batholith was controlled by

northeast-trending and east-trending fault sets. Satellite plutons

associated with the batholith were emplaced along northwesttrending faults. The Boulder batholith was emplaced at about

78-70 Ma and therefore is older than the Tertiary intrusions in

Idaho. This Cretaceous age adds further support to the idea that

in Montana and Idaho some northeast and northwest faults are

older than Tertiary and have a long history of movement.

A number of north-trending faults were mapped or inferred

in the western part of the Hailey 1°×2° quadrangle. One of

these, the Pine-Featherville fault, north of Dog Mountain, separates aplite, pegmatite, and metamorphic rocks to the east of

Pine from granodiorite to the west. The road follows the fault

from Pine to Featherville. The pinnacles near Tollgate Creek

that are visible just west of the Pine-Featherville road are highly

sheared granodiorite believed to be related to the faulting. Several hot springs, including a spring at the bridge over the South

Fork at Dixie Gulch, Paradise Hot Springs, and hot springs on

Warm Springs Creek northeast of Featherville, are on the trace

of the fault. The age of the north-trending faults is unknown but

the faults are probably very young and are perhaps the same age

as the east-trending faults shown on the geologic map of the

Figure 21. Anderson Ranch Dam, Idaho. Pegmatite and aplite dikes in granodiorite are the main rock unit, and a number of

basalt dikes crosscut the granitic rocks.

North-Trending Faults

×
Geology 21

Figure 22. Elk Creek fault (segment of the Deer Park fault) on the James Creek road from Rocky Bar to Atlanta, Idaho. Lightcolored outcrop is gouge from faulted biotite granodiorite. Fault trace is in the middle of Elk Creek. Note the similarity to the Cow 

Creek fault shown on figure 8.

Figure 23. Hot Creek fault, just north of the Elk Creek segment of the Deer Park fault, Idaho. Steel Peak, composed of Tertiary 

granite, is to the right of hot Creek and biotite granodiorite to the left.
22 Geology and Mineral Deposits of Part of the Western Half of the Hailey 1°×2° Quadrangle, Idaho

EXPLANATION FOR FIGURE 24

A

B

C

D

E

F

G

H

I

J

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

Mining districts

Neal

Yuba-Atlanta Hill

Skeleton Creek

Roaring River

Rocky Bar—Includes Red Warrior and

Bear Creek mining districts

Featherville

Pine (Pine Grove)

Lime Creek

Dixie

Volcano

Mines and other properties

Homestake-Hidden Treasure

Daisy

Sunbeam-Sunshine

Twin Springs placer

Sheep Creek placer

Hermada

Atlanta Hill

El Oro

Red Horse or Frazier

Old Sam or Turner

Decker Horstenstine

Rinebold

Avalanche-Richmond

Vibrator

Vishnu (Clifton Bell)

Morning Star (Canada mill)

Ada-Elmore

Independence

Mountain Goat

Ophir

Spanish Town

Wide West

Bonaparte mine

Marsh Creek mine

Shake Creek prospect

South Park Dredging Company

Franklin

Mountain View

President, Hawthorne, Jingo, Hornet

Highland Mary

Copper King

Mountain View tungsten

King shaft

Index

Cat Creek mine

Bowerman group

Blackstone

Volcano

Revenue

Index group

Hailey 1°×2° quadrangle (Worl and others, 1991). Some of 

these structures such as the Pine-Featherville fault, are oriented 

about 45° to the northwest-trending basin and range faults and 

may be tangential shears between two such basin and range 

structures.

Geologic Summary

The western half of the Hailey 1°×2° quadrangle is dominated by rocks of the Idaho batholith that are overlain by metamorphic rocks of uncertain age. Compression during the 

Cretaceous may be recorded by decollements at House Mountain and Chimney Peak. A complex sequence of faults that 

formed or were reactivated during Late Cretaceous to middle 

Tertiary extension have broken the area into a series of rhomboid-shaped blocks that have been complexly tilted. Formation of Eocene and Miocene volcanic and plutonic rocks 

accompanied extensional activity. This faulting and associated 

plutonic and volcanic activity are related to the ore deposits in 

the area.

Mineral Deposits

The purpose of the Hailey CUSMAP program was to evaluate the mineral potential of the Hailey 1°×2° quadrangle. The 

western half of the Hailey quadrangle contains several hundred 

mines and prospects in 18 mining districts. The following sections describe the major deposits in nine of these districts (fig. 

24), including the Skeleton Creek, Lime Creek, Rocky Bar, 

Neal, Pine, Volcano, Dixie, Featherville, and Roaring River mining districts and several deposits that are outside these district 

boundaries. The important deposits near Idaho City and Atlanta 

(Yuba district) are discussed by Kiilsgaard, Scanlan, and Stewart (in press) and Kiilsgaard and Bacon (in press).

Periods of Mineralization

Mineral deposits in the western part of the Hailey 1°×2°

quadrangle can be divided into three main groups: Late Cretaceous-Paleocene deposits, Eocene deposits, and possible 

Miocene and younger deposits. The distinction between Late 

Cretaceous-Paleocene deposits and Eocene deposits, if one 

exists, is not totally clear at this time. It is possible that mineralization was almost continuous from 70 to 40 Ma. The division is 

based on several Ar40/Ar39 dates on sericite from mines and 

more dating and study is needed to solve this problem. 

Late Cretaceous-Paleocene Deposits

The age of mineralization at Rocky Bar and Atlanta has 

been debated for many years. New Ar40/

39 dates for these 

deposits (Snee and Kunk, 1989) indicate a Late CretaceousPaleocene age for the mineralization at both locations. Deposits 

in these areas are within northeast-trending shear zones that 

were assumed to be Eocene. Therefore, some of the northeast 

structures had movement prior to the Eocene. Deposits in the 

Yuba district (Atlanta Hill) are hosted in Cretaceous granodiorite preserved in a graben between the Montezuma and Deer Park 

faults. The mines at Rocky Bar are just west of this graben and 

are also hosted in Cretaceous granodiorite.

Some deposits known to be Eocene in age in the TransChallis fault system are associated with rhyolite intrusive rocks 

of Eocene age. Rhyolite dikes are rare at Rocky Bar and at 

Atlanta Hill. At Rocky Bar, a thin rhyolite dike crosscuts a mineralized shear zone and is definitely younger than the mineralized rock (Dave Cockrum, GEXA, oral commun., 1989). 

Anderson (1943) noted a similar relationship near old Spanish 

Town in the Rocky Bar district. By inference with rhyolite of 

known age elsewhere, the mineralization is pre-Eocene. 
23

1 2

3

4

5

6

7

8

9

10

11

12 13 14

15

16

17

1819

20

21

22 23

24

25

26

27 28

29 30

31

32

33

34

35

37 36

38 40 39

A

B C

D

E

F

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H

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J

0 2 4 MILES

0 2 4 KILOMETERS

20

84

FOOTHILLS

ROAD

Boardman Cr

Mountain Home

Dixie

Mayfield

Prairie

Twin Springs

Rocky Bar

Atlanta

Featherville

Hill City

Fairfield

Idaho

City

Pine

Bennett

Mountain

Cathedral

Rocks

Arrowrock Dam

Anderson Ranch Dam

Windy Gap

Smith Prairie

Moores Flat

Camas Prairie

Danskin

Bridge

Bennett

Creek

Basin

Iron Mtn

Bald Mtn

Gunsight Pk

Cayuse Pt

Rose Pk

Steel Mtn

Three

Point

Mtn

Boise

Blakes Creek Road

Thomson Ranch

Dog Creek

Campground

Big Smoky

Guard Sta

Trinity Mtn

Smoky Dome

House Mtn

Wood Creek Mtn

Chimney Peak

Danskin

Peak

Lime Cr

Willow Cr

Fall Cr

Bowns Cr

Mannencke Cr

Cow Cr

Ear Cr

Sheep Cr

Mormon Reservoir

Grimes Cr

Mores Cr

River Roaring

Hot Cr

Bear Cr

Elk Cr

South Fork Boise River

South Fork Boise River

Middle Fork Boise River

Middle Fork Boise River

Feather R

Willow Cr

44°

43°

116°

Work in the Elk City 1°×2° quadrangle to the north (Lewis 

and others, 1990) suggests that gold deposits near Elk City are 

probably Cretaceous-Paleocene in age and are similar to deposits in the Gospel Hump area dated as Cretaceous by (Lund and 

others, 1986). As noted, mineralization at Rocky Bar, Atlanta, 

and in other districts may also be Cretaceous in age. 

Eocene Deposits

The Trans-Challis fault system (Kiilsgaard and others, 

1986, 1989) contains many gold mines, including the mines at 

Idaho City (about 3 million ounces, the largest gold producing 

area in Idaho) and the recently discovered Beartrack property 

Mineral Deposits

Figure 24 (above and previous page). Map showing location of selected mineral deposits and mining districts in the western part of the 

Hailey 1°×2° quadrangle, Idaho modified from Gustafson (1987) and Ross (1941). The Neal and Lime Creek districts (informal) were not included in Ross’s map and, the Dixie district, which was shown incorrectly on Ross’s map is shown in its correct location. 
24 Geology and Mineral Deposits of Part of the Western Half of the Hailey 1°×2° Quadrangle, Idaho

north of Salmon (probably the largest single lode gold discovery 

in the State’s history). Northeast-trending structures are important controls for deposits elsewhere in the western part of the 

Hailey quadrangle. Several mines in the Willow Creek-Bear 

Creek drainage, including the Red Horse and the El Oro, are 

directly on a northeast-trending structure. Likewise, the mines 

in the Lime Creek district and several adjacent prospects are on 

the northeast-trending Moores Flat fault. 

The association of rhyolite and northeast-trending structures that is so dominant in parts of the Trans-Challis fault system may also be true for the Hailey 1°×2° quadrangle. The Gold 

Hill mine in the Centerville district (Boise Basin) is hosted in a 

rhyolite contained in a northeast-trending shear zone. Deposits 

in the Neal mining district are in northeast-trending shear zones, 

and Three Point Mountain, just west of the deposits, contains a 

rhyolite dike swarm. A rhyolite dike is also exposed just west of 

the King shaft in the Dixie mining district.

Possible Miocene and Younger Deposits

Elsewhere in Idaho and Oregon, for example, the DeLamar 

mine in Owyhee County, the Tolman mine in Cassia County, the 

Idaho Almaden mine in Washington County, and several new 

prospects in Malheur County, Oregon, epithermal basin and 

range mineralization is well documented. These “hot springs”

deposits are hosted in sandstone, other sedimentary rocks, and 

rhyolite intrusive rocks but not in batholith rocks. The low grade 

and apparent paucity of basin and range deposits in the batholith 

suggest that granitic rocks are a poor host for this type of ore 

deposit. Basin and range related mineralization probably was 

not very important in the study area.

Several mines or prospects including the Marsh Creek 

mine, the Shake Creek prospect, and the Bonaparte mine (and 

prospects north of the mine), are astride or close to the Iron 

Mountain segment of the Deer Park fault, which is believed to be 

a basin and range structure. None of these deposits have had 

substantial development, based on the size of mine dumps and 

production figures available in the literature. Adularia from the 

Marsh Creek mine (R.E. Sanford, oral commun., 1991) was 

dated by Ar40/Ar39 methods at 39.3 Ma (Eocene). The Hermada antimony mine (described by Popoff, 1953) (not visited by 

the author), on the East Fork of Swanholm Creek, is also very 

close to the Deer Park fault. An Ar40/Ar39 date of 61.2 Ma (Snee 

and Kunk, 1989) indicates that mineralization at the Hermada 

mine is older than basin and range extension. If the Marsh 

Creek and Hermada mines are in some way related to the Deer 

Park fault, then there was pre-basin and range movement along 

this structure. 

Neal Mining District by Thor H. Kiilsgaard

and Earl H. Bennett

The Neal mining district is about 15 mi east of Boise, east 

and southeast of Three Point Mountain. The northern part of the 

district is along the divide between Wood Creek and Blacks 

Creek (figs. 24, 25). Access is from Interstate 80 via the Blacks 

Creek exit or by dirt road south from the town of Prairie. The 

only published geologic description of the district is by 

Lindgren (1898).

Production

Lindgren (1898) estimated a value of $200,000 for gold 

produced from the district through 1897. Using a value of 

$20.67 per ounce of gold, the price paid for 1000-fine gold dring 

the period of production, the $200,000 represents a production 

of 9,675 ounces. Unpublished data from the U.S. Bureau of 

Mines, for 1901 to 1991 show production of 20,135 ounces of 

gold and 15,428 ounces of silver (table 1). Placer production 

from the district has been minimal. Assuming some error in the 

records and no production data for the years 1898, 1899, and 

1900, it is reasonable to believe the district has produced at least 

30,000 ounces of gold.

The most productive mines in the district have been the 

Homestake-Hidden Treasure, the Golden Eagle and the Daisy; 

smaller producers include the Sunset and the SunshineSunbeam. Of these mines, the Homestake-Hidden Treasure and 

the Daisy are on the same vein zone.

History

Lindgren’s (1898) description of veins in the district is 

based on notes by F.D. Howe, who was superintendent of the 

Hidden Treasure mine. Veins of the district have a common N. 

70°–83° E. trend and the same general dip to the south. Based 

on form, the veins can be differentiated into three classes: (1) 

veins filling larger fault fissures, on which are located the principal mines; (2) veins along minor shearing planes of the granite, 

more or less irregular, but generally containing high-grade ore; 

and (3) veins of hard white quartz that do contain precious metals. The major veins are displaced by north-trending faults. 

Much of the gold is free, but some is in pyrite. The veins also 

contain minor accessory sulfide minerals, including sphalerite 

and galena.

Lindgren (1898) described the country rock of the district 

as gray granite cut by numerous dikes. He called attention to 

large syenite porphyry dikes that cross Blacks Creek about 2.5 

mi southwest of the Daisy shaft and to narrow lamprophyre 

dikes that follow along the vein at the Homestake and the High 

Five mines. He thought that the lamprophyre dikes probably 

antedate the veins.

Wells (1983) provided a brief overview of early discoveries 

in the Neal mining district. In December 1888, Arthur Neal, 

enroute to Boise with his pack string, discovered mineralized 

float. He found the mineralized source the following year and, 

with his partner George House, began mine development. 

These and other early workers were hampered by a lack of 

capital and water in the dry region. Similar to other districts in 

Idaho, most of the mines in the Neal mining district were 

financed and operated by eastern capitalists.

The following historical summary of mining activity in the 

Neal mining district was taken from annual reports on the 

mining industry of Idaho by the Idaho State Mine Inspector, 
25

0 1000 FEET

Daisy

Mine

Confidence

Mine

Homestake

Mine

Workings

Mine roads

Mineralized

outcrops Hidden

Treasure

Mine

Wood Creek road

Blacks Creek road

Pass

EXPLANATION

Adit

Mine workings

Structure

N

Figure 25. Location map of the Neal mining district, Idaho. Location of mining district is shown on figure 24.

Table 1. Gold-silver production from mines of the Neal mining district, Idaho, 1902–1991.

 [Compiled from U.S. Bureau of Mines unpublished production records]

1

May be mislocated. Production form shows that mine is in the Neal mining district, but section, range and township 

location figures, also on the production form, indicate that the ore was mined from the Rocky Bar area.

Property or operator Tons of ore Gold

(ounces)

Silver

(ounces)

Production

years

Homestake-Hidden Treasure 35,644 13,961 10,219 1902–1941

Daisy 1,888 1,121 1,260 1902–1906

Golden Eagle 11,911 4,138 2,864 1902–1915

Sunset 75 68 32 1923–1939

Sunshine-Sunbeam 100 45 50 1902

Flat Creek 26 8 2 1938

Elmore1 702 768 951 1902–1904

Various operators 75 54 50 1908–1939

Total--------------------------------- 50,421 20,163 15,428 —

Mineral Deposits
26 Geology and Mineral Deposits of Part of the Western Half of the Hailey 1° 2° Quadrangle, Idaho

(1902–1979), from U.S. Geological Survey reports on mineral

resources of the United States (1903-1924), from U.S. Bureau of

Mines reports on mineral resources of the United States (1924–

32), and from U.S. Bureau of Mines mineral yearbooks (1924–

1989).

In 1902, New York capitalists planned on building a new

mill at the Hidden Treasure mine. Ore from this mine previously

had been processed in an old Balbach mill. The Daisy mine was

sold by George Bredhoeft to a Chicago and Wisconsin interest

for $225,000. In 1903, the Hidden Treasure, Homestake, and

Ella Hill mines were all operating. The Homestake had a 200-ft

deep vertical shaft and several thousand feet of crosscuts.

In 1902–03, the Ella Hill mine was being developed by a

long tunnel, and ore was found at the bottom of a 55 ft shaft in

the No. 13 mine. The Overlook mine was being developed by

eastern interests under the direction of J.W. Murphy.

In 1904, considerable work was done at the Homestake

mine, and progress was made at the Ella Hill, South Star, and

Badger properties. Good ore was discovered at the Daisy. In

1907, the Daisy and Homestake mines were operated by the

George F. Roth Company of Rochester, New York. This company also has been referred to as the Homestake and Mountaineer Mining Company. The company employed 20 men and had

constructed a 10-stamp mill. Mine workings included a 2,000-

foot adit and two shafts, 200 and 400 ft deep. The company

did 1,500 ft of development work. A 30-ton-per-day cyanide

plant was added in 1908 and another 2,000 ft of underground

work completed. A new 10-stamp mill and a 60-ton-per-day

cyanide plant were installed in 1910. By then, the main shaft

was 600 ft deep.

By 1911, the Daisy, Homestake and Hidden Treasure

mines (referred to by the U.S. Bureau of Mines as the Roth

property) were connected by underground workings. A 3,000-

foot adit connected underground workings with the mill, which

was on the Hidden Treasure property. Veins were persistent to

a depth of 500 ft and contained refractory ore (gold in pyrite)

and some galena and sphalerite. Sixty-five men worked in the

mine and mill. The stamp mill was upgraded by installation of

new plates, and Pachuca tanks were added. The year 1911, a

record year for mine and district production, 17,292 tons of ore

were mined.

Mining continued at the Roth property until 1915, but the

heyday of operation was past and the property never again

approached the production rate of 1911. Very little ore has

been produced from the property since l915. The mill burned

in May 1913, but was rebuilt. About 440 tons of ore were

mined in 1923–24 and a total of 15 tons of ore in 1925 and in

1938–41.

In 1936, the Cordova Mining Company did 500 ft of

development work at the Homestake-Hidden Treasure mine,

using a crew of six men. The company opened the main adit for

515 ft and did 192 ft of additional underground work the following year. In 1938, Cordova leased the property to H.D.

Languille, but no further development activity was reported.

The Golden Eagle mine, one of the older mines in the Neal

mining district, is about 5 mi southwest of the Homestake mine.

Little evidence of the surface plant of the mine was recognizable

in 1990; however, the caved, inclined shaft that led to the principal underground workings is located S. 88 W. and 1,500 ft distant from the intersection of the Blacks Creek and the Mayfield

roads.

The Golden Eagle produced 3,000 tons of ore in 1902. By

1903, the mine was developed by a 300-foot shaft from which

three levels were driven. A new company was incorporated in

1904 to take over the mine, and an 80-ton Chilean mill was

built. A new shaft, the one referred to in the preceding paragraph, was started several hundred feet west of the old one. The

new inclined shaft eventually was sunk to a depth of more than

375 ft and several levels were driven from it. Ore shoots ranged

from 45 to 105 ft in strike length and extended both east and

west from the shaft. The vein ranged from 5 to 20 ft in width

and had average gold values of $10 to $15 per ton (with gold at

$20.67 per ounce). In 1906, its most productive year, the mine

produced 6,170 tons of ore. There is no record of production

from the mine after l915.

Several prospects and small mines in the Neal mining district sporadically produced small amounts of ore. These include

the Sunset, from which 75 tons of ore were produced during the

period 1922–1938; Flat Creek, from which 26 tons were mined

in 1938; Sunshine; Elmore; and Badger. Minor tonnages of ore

from these and other properties are recorded under the name of

the operator, who may have been a lease holder who produced

ore from one of the better known mines such as the Homestake.

The location of such minor productive sites cannot be ascertained from existing records.

Geologic Setting

The Neal mining district is underlain by biotite granodiorite of the Idaho batholith that has been intruded by a variety of

Tertiary dikes, most common by rhyolite. Most of the dikes

strike northeast and dip steeply, generally conforming in attitude

to other swarms of dikes exposed elsewhere in the Hailey

quadrangle (Worl and others, 1991). Gouge along the walls of

some of the dikes exposed in bulldozed cuts suggests that the

dikes were intruded along pre-existing faults.

The most conspicuous dikes in the Neal mining district

are large, long, north-striking, brownish dikes that cross Blacks

Creek road about 2.5 mi southwest of the Daisy shaft. In hand

specimen the dike rock appears to be rhyolite, but analytical

determinations of three samples indicate an average SiO2 content of about 65 percent, too low for rhyolite. The rock also

has an unusually high K2O content, an average of 4.86 percent, and it contains hornblende. The dike rock was classed as

syenite porphyry by Lindgren (1898), but modern terminology

suggests that it is quartz trachyte. Northeast-striking dikes of

Homestake, Hidden Treasure, and Daisy Mines

Golden Eagle Mine

Other Properties

1°×2°

×
27

similar chemical composition crop out in the vicinity of the old 

mine workings.

A discontinuous series of lamprophyric dikes extend along 

the Daisy-Homestake-Hidden Treasure vein zone from the Confidence mine in the southwest to beyond the Homestake claim in 

the northeast. The dike rock is dark green to black and dense 

and contains conspicuous phenocrysts of biotite. Where seen in 

bulldozed cuts, the dike rock is sheared and hydrothermally 

altered along northeast-trending faults, as is the contiguous, 

biotite granodiorite. At most exposures, the dikes range from a 

few inches to 3–4 ft in thickness; however, about 250 feet north 

of the Daisy shaft, several strands of lamprophyric dike make up 

an aggregate thickness of 25 ft. At that location, small pods of 

mineralized quartz in the lamprophyre indicate that the dike is 

pre-ore, similar to a lamprophyre dike observed by Lindgren 

(1898) in the middle of a 4-foot vein at the Homestake mine. 

There are no age data for these lamprophyric dikes; they may be 

Cretaceous in age and related to the Idaho batholith rather than 

Tertiary in age, similar to other dikes of the district.

Bounding the more mineralized part of the northern part of 

the Neal mining district are two high-angle northeast-striking 

faults, one of which, the Blacks Creek fault, has been traced for 

several miles of strike length. The faults probably formed 

before the dikes, and, in part, may have guided emplacement of 

the dikes.

Principal Veins

Principal veins of the Neal mining district strike N. 

65°−85° E. and dip 40°–45° SE. Clear vitreous quartz is the 

chief vein mineral, and at the outcrop it is stained a rusty color 

by oxidized pyrite. Pyrite casts in quartz are common, and 

auriferous pyrite on lower levels of the Homestake-Hidden Treasure mines was mentioned by Lindgren (1898). The mineralized 

quartz is discontinuous along the vein zone. In places no quartz 

is visible, but in other places the mineralized shoots are as thick 

as several feet. Much of the vein material is altered, sheared 

biotite granodiorite. Fault gouge, generally a few inches thick, 

is common along the veins, although 4 ft of gouge and clay is 

present along the hanging wall of the Golden Eagle vein.

Two northeast-trending veins crop out in the vicinity of the 

Daisy shaft and continue northeast through the Homestake patented claim. The veins are subparallel with the northeast-trending faults and the dikes in the area. The location of the veins 

probably was controlled by the northeast-trending shears. The 

southernmost of the two veins may to have been the principal 

vein worked in the Daisy-Homestake-Hidden Treasure mines. 

The vein is well exposed on the ridge 300 ft northeast of the 

Daisy shaft and projects very close to the collar of the shaft, 

which was obliterated by bulldozing in 1989. The vein continues northeast of the claim-block boundary, and prospect pits 

indicate that it or a nearby subparallel vein continues for more 

than 2,000 ft to the northeast beyond the patented claim-block 

boundary. Old workings have obliterated the vein outcrop at the 

High Five mine, although field evidence indicates that the vein 

explored at that mine strikes northeast, and probably is a continuation of the Daisy-Homestake-Hidden Treasure vein or another 

vein of that pattern. The northernmost of the two veins may be 

en echelon in nature because, although it crops out on the ridge 

northeast of the Daisy shaft, it was not found in holes drilled 

near the east end of the claim block and probably had pinched 

out by that point.

Two other northeast-trending veins, about 2,000 ft south of 

the Daisy shaft, have been tested by underground workings and 

prospect pits. Pieces of mineralized quartz on the dump of an 

old caved adit suggest that the adit was driven on a vein that may 

be traced on the outcrop, but no recorded ore production can be 

associated with the workings. Surface exposures of the vein 

pass close to the northern edge of the Ella Hill claim and may be 

the vein that was explored from that claim.

The Golden Eagle vein crops out about 5 mi southwest of 

the Daisy shaft. The vein strikes N. 70° E., dips about 45° SE, 

and has been traced along the outcrop for more than 1,000 ft. 

Country rock of the vein is biotite granodiorite of the Idaho 

batholith, that is intenively hydrothermally altered as far as 15 ft 

from the vein. Feldspar in the granodiorite has been altered to 

sericite or various clay minerals. Drill holes through the vein 

indicate that as much as 4 ft of clay extends along the vein hanging wall. According the Idaho State Mine Inspector’s report for 

1904, the gold-bearing width of the vein zone ranged from 5 to 

25 ft and had average gold values of $10 to $15 per ton (price of 

gold $20.67 per ounce).

A northeast-striking vein is exposed in a bulldozed open 

cut about 2.4 mi southwest of the Daisy shaft, north of the 

Blacks Creek road, SW1/4 sec. 23, T. 2 N., R. 4 E. The vein 

strikes N. 70° E., dips southeast, and consists of sheared biotite 

granodiorite and iron-stained quartz. Casts of sulfide minerals 

are present in the quartz, but the minerals themselves have been 

oxidized and removed. The vein plots along the southwest projection of the Daisy-Homestake-Hidden Treasure vein pattern. 

Judging from the dump, the bulldozed open cut may have obliterated an adit that formerly explored the vein.

In the Neal mining district there are many old prospect pits 

and small dumps, on some of which are fragments of mineralized quartz, where no vein outcrops could be seen and no vein 

attitudes determined.

Other Veins

Although the principal veins in the northern part of the 

Neal mining district strike northeast, subparallel with the major 

faults and dikes of the district, other, smaller veins intersect the 

northeast-trending structures at acute angles. These veins strike 

northwest and may be gash veins; that is, veins that formed 

along tensional fractures created by differential strike-slip 

movement along the regional northeast-trending faults. Typical 

of these gash veins is the vein at the Sunshine property that was 

being explored in 1989. That vein strikes N. 75° W., dips 55°

SW., is about 4 ft thick, and consists of sheared and altered 

biotite granodiorite.

Two other northwest-striking gash veins, both only a few 

inches thick, are exposed in prospect pits east of the patented 

claim block. Because of their small size, neither is shown on 

figure 24.

A more conspicuous example of a gash vein of this pattern 

crops out northwest of Three Point Mountain, on the north side 

Mineral Deposits
28 Geology and Mineral Deposits of Part of the Western Half of the Hailey 1° 2° Quadrangle, Idaho

of Charcoal Creek, NW1/4 sec. 9, T. 2 N., R. 4 E. That vein,

which was explored by an adit that was caved at the portal in

1987, strikes N. 60° W. and dips 55° NE. Where exposed, the

vein is about 1 ft thick and consists of sheared biotite granodiorite and iron-stained quartz.

Comparison of Veins in the Neal Mining District With

Those of the Quartzburg and Yuba Mining Districts

The principal veins of the Neal miningdistrict are similar in

many respects to the main veins in the Quartzburg and Yuba

mining districts (fig. 24). The veins strike northeast, subparallel

with regional northeast-trending faults that probably exerted

structural control on the location of the veins. The veins also

are subparallel with Tertiary dikes that have been intruded along

shears related to the regional faults. Quartz is the principal mineral of the veins, which have been worked primarily for gold,

although more silver has been mined than gold. Minerals from

which copper, lead, and zinc have been extracted also are

present in the veins but in negligible amounts. Both DaisyHomestake-Hidden Treasure vein of the Neal mining district

and the Atlanta lode of the Yuba mining district follow premineralization lamprophyric dikes that may be of Cretaceous

rather than Tertiary age.

At Quartzburg, the veins cut across rhyolite dikes that

intrude quartz monzodiorite of Eocene age; thus, the veins can

be no older than Eocene. By comparison, in the Neal mining

district at the Jackson prospect on Charcoal Creek, west of Three

Point Mountain, Lindgren (1898) noted that gold ore occurred as

joint coatings and impregnations in a quartz porphyry dike.

Based on our examination of the Jackson prospect, we describe

the dike as rhyolite, one of the many Tertiary rhyolite dikes in

the area. Our classification places the gold ore as post-dike, or

Tertiary, in age. A somewhat similar comparison was made from

findings on a dump south of the Daisy shaft. There, a dump

fragment of dacite porphyry dike contained a section of an ironstained quartz veinlet. There was insufficient quartz for a sample, but the quartz was obviously mineralized and was similar in

appearance to quartz on mine dumps of the Neal mining district.

Similar dacite dikes elsewhere in the Hailey 1 2 quadrangle

are no older than Eocene; thus the Neal ore probably is no older

than Eocene. On the other hand, if the lamprophyric dikes along

the Daisy-Homestake-Hidden Treasure vein and along the

Atlanta lode in the Yuba mining district are of Cretaceous age,

the ore in the veins at both locations could be of Cretaceous age.

Mineral Exploration of the Neal Mining District

in the 1980’s

Centennial Mine Company, a subsidiary of Meyer

Resources, began an exploration program in the northern part of

the district in February 1989. The program consisted of drilling

reverse circulation holes and was confined mostly to the Daisy,

Homestake, and Mountaineer patented claims in the northern

part of a block of patented claims (fig. 25). It concentrated on

exploration of the Daisy-Homestake-Hidden Treasure vein zone

and was confined mostly to the area extending northeast from

the vicinity of the Daisy shaft to the claim block boundary.

Some holes were drilled on the north-trending ridge that is

3,000 ft northeast of the Daisy shaft. A total of 205 holes were

drilled.

According to James Carver, Project Geologist, Centennial

Mine Company, the objective of the exploration program was to

determine whether a large block of ground could be outlined

that would be amenable to open-pit mining. Because much of

the southeast-dipping vein zone traverses a southeast-dipping

hillside, it was reasoned that a minimum of barren overburden

would have to be removed to reach mineralized ground.

Drilling results indicated that mineralized bodies along the

vein zone are discontinuous. Some holes were essentially barren, whereas others had mineralized intercepts of as much as 40

ft. Whether such intercepts represented one vein or more than

one vein was indefinite. Lamprophyric dike intercepts were

found all along the vein zone. Neither the drill-hole data nor

surface geologic mapping confirmed the existence of northtrending offsetting faults, as reported by Lindgren (1898).

Instead, the mineralized orebodies probably are en echelon

along the vein zone and swell and pinch out.

According to Donald Blow, lease holder of the patented

claim block while the exploratory work was underway, the drilling confirmed a mineralized block of 356,000 tons that averaged 0.076 ounces of gold per ton. The drilled resources were

deemed inadequate for the open-pit, heap-leach mining and processing operation planned by Centennial Mine Co., which terminated its exploration program in 1990 and dropped its Neal

property holdings.

Ten holes, the aggregate length of which totals 12,000 ft,

were drilled on the Golden Eagle vein in 1986–87 by the Yanke

Company, Boise, Idaho (Dan Yanke, oral commun.,1991). The

holes were drilled on both sides of the caved shaft of the Golden

Eagle mine, extending for about 200 ft northeast and southwest

from the shaft. Drilled intercepts showed a 3- to 4-foot-thick

zone of clay, gouge, and altered granodiorite along the hanging

wall of the Golden Eagle vein zone, a zone that ranged from 3 to

20 ft in thickness. One hole contained 13 ft of material that

averaged 5 ounces of gold per ton, and another hole contained 4

ft of 0.50 ounces of gold per ton. A hole that extended well into

the vein footwall encountered a small, parallel vein about 60 ft

into the footwall of the Golden Eagle vein.

The Confidence mine, 1,500 ft southwest of the Daisy

shaft, west of the Blacks Creek road, and immediately southwest of the block of patented claims, was developed on what is

probably the southwest extension of the Daisy-HomestakeHidden Treasure vein zone. The J and D Placer and Lode

Daisy-Homestake-Mountaineer Area

Golden Eagle Mine

Confidence Mine

×
29

Mining Co. conducted development work at the mine in 1987.

A short inclined winze was sunk to the southwest in the vein,

from which a short drift was driven to the collar of another

inclined winze in the vein, from the base of which a short drift

was driven to the southwest. These workings were driven

beneath an old inaccessible adit that followed the vein and from

which high-grade ore reportedly had been mined. The face of

the lower drift was about 125 ft from the portal of the upper

winze and an estimated 50 ft below the ground surface. The

mine workings were driven along the hanging wall of a lamprophyre dike, although the final 10 ft of the lower drift was entirely

within the dike. A few hundred pounds of mineralized quartz

and granodiorite was obtained from pockets along the vein

which was processed in a small mill at the mine portal. The

mining program was unsuccessful and work at the mine terminated in l987 or early l988.

In 1989, a northwest-striking vein on the Sunshine claim

was being explored by E. Loveland of Boise, who was using a

small front-end loader to excavate an open cut on the vein. The

open cut was only a few feet long. There was no evidence of

additional work at the site in 1990.

The Blacks Creek prospect is near the junction of the

Blacks Creek and the Mayfield (Foot Hills) roads, about 100 ft

west of the Blacks Creek road and about an equal distance north

of the Mayfield road. In 1987, Dan Yanke of Boise sank a shaft

to a depth of about 15 ft at the prospect to test some small veinlets of mineralized quartz in the biotite granodiorite. The work

was not encouraging, and as of 1991 no further work had been

done at the site.

Pine (Pine Grove) Mining District

The Pine (Pine Grove) mining district is just south of the

town of Pine at the north end of Anderson Ranch Reservoir. A

good dirt road connects U.S. Highway 20 to a paved road that

goes from Lime Creek to Pine. The only published descriptions

of this district, including the Franklin mine, the most significant

producer, are in Ballard (1928) and in various yearly reports of

the Idaho State Mine Inspector.

Franklin Mine

The Idaho State Mine Inspector (1919) noted that the

Franklin mine had produced some $400,000 in gold by 1919.

The U.S. Bureau of Mines indicated that the mine produced

18,384 ounces of gold and 12,611 ounces of silver from 29,692

tons of ore and 1,001 tons of tailings from 1902 until the mine

closed in the 1930’s. Ballard (1928) gave the production at

$750,000, based on U.S. Mint records.

According to the Idaho State Mine Inspector (1909), the

Franklin vein is in a fissure in granite; the vein strikes N. 20

W. and dips steeply east. Numerous aplite and pegmatite dikes

are 275 ft to the west of the mine (the mine is near the northern edge of the aplite and pegmatite zone described previously). The lowest level of the mine was 450 ft below the apex

and 900 ft of drifting on this level found good ore. The inspector continued, “The main ore shoot has a pitch between the surface and the No. 2 level of 45 degrees to the south. This pitch

necessitated drifting north a considerable distance to find the

ore from a point vertically under where it was struck in No. 1

level.” In 1928, Ballard noted that the mine had been added to

the nearby W.R. Deckard property that contained the Objective

vein. The Objective vein is 645 ft east of the Franklin and parallel with it. Ballard noted that both veins were fissures that

contained quartz and pyrite and occasional “kidneys” of galena

and sphalerite. High-grade gold in the upper workings (to a

depth of 450 ft at the No. 3 level) concentrated in an oxide

zone similar to other deposits in the area. Below the No. 3

level, sulfide ores were dominant.

The following account of the early development of the

Franklin mine and other mines near Pine is from Wells (1983).

Gold was discovered in a blind tunnel at the Franklin mine on

May 16, 1887, by prospectors working for Oliver Sloan, who

lived in Pine Grove. By 1888, a gold rush was underway and a

10-stamp mill had been constructed at the mine by a St. Louis

company. Sloan sold his interest and developed the town of

Pine to serve the miners. British investment spurred the development of these mines in 1892. In 1897, the Franklin mine

was sold.

The following history from 1902 to date is taken from

Idaho State Mine Inspectors reports (1902-1979), the U.S. Geological Survey (1905-1923), and U.S. Bureau of Mines (1924–

1989) yearbooks, and various reports by the Idaho Bureau of

Mines and Geology and the Idaho Geological Survey.

In 1902, the Franklin mine had two drifts, and a 10-stamp

mill was running. In 1903, the Idaho State Mine Inspector

described a remarkable gold discovery at the Franklin mine,

owned by Robert P. Chattin. The inspector noted that the mine

had been developed 10 years previously by a company that

failed and had been equipped with a 10-stamp mill. Chattin

obtained the property in 1902 and had driven a 207-foot-long

crosscut into an area where rich float had been found. The ore

was in a shear zone in granite that included a green dike. Chattin extracted 3,000 tons of ore averaging $25 per ton in free

gold. A new crosscut tunnel, started in August, 145 ft below the

original tunnel, found the ore. The company planned on driving

another 700-foot-long tunnel at the base of the hill. In 1904, the

mine produced $70,000 in gold from the 10-stamp mill, despite

the fact that the mill was inoperative about half of the time.

About 2,000 ft of new drifts were completed during the year. At

the No. 2 crosscut, a 1,000-foot-long drift was developed with

700 ft in ore. The new 700-foot-long tunnel (planned 2 years

before) was completed from the valley level, 204 ft below the

No. 2 and 600 ft below the apex. Little ore was discovered on

this level despite of 900 ft of drifting done during the next few

years. In 1905, a new 100-ton-per-day cyanide plant was constructed for processing tailings from the stamp mill (15,000 tons

had accumulated during the previous 2.5 years). The Franklin

Mineral Deposits

Sunshine Mine

Blacks Creek Prospect
30 Geology and Mineral Deposits of Part of the Western Half of the Hailey 1°×2° Quadrangle, Idaho

produced a record 4,718 ounces of gold and 2,276 ounces of silver from 8,700 tons of ore and 1,000 tons of old tailings. Sixteen men worked the property, which reported large reserves.

In 1906, C.H. Gold Mines Company operated the Franklin 

mine with 35 men for part of the year. Although the water-powered mill was closed in the fall by an early freeze, the operation 

grossed $50,000 in 5 months. The next year, the mine operated 

with a force of 30 men and was developed to a depth of 400 ft. 

The ore in the lower workings was more refractory. A setback 

occurred in May 1908, when fire destroyed the stamp mill and 

cyanide plant. The mine was idle in 1909 but reopened the following year with a new 25 ton-per-day, 5-stamp mill and plant 

that had cyanide capability. Most of the production was from the 

middle tunnel level because, as noted, there was no ore in the 

lower level. A tramway carried the ore to the valley bottom, and 

the ore was then hauled one-third of a mile to the mill. The mill 

was enlarged to 10 stamps in 1910, and bullion was shipped 

from May to December. The Franklin mine operated for a short 

time in 1911. Lessees processed some ore by cyanide extraction 

in 1914.

In 1925, the Franklin Consolidated Gold Mines Company 

acquired the mine. The following year, the company rehabilitated old workings and started new development but suspended 

operations late in the year due to litigation. Some cleanup ore 

from the mine worth $1,400 was shipped in 1931 to Midvale, 

Utah. Lessees drove a new tunnel at the mine in 1932. In 1935, 

the Gold King Mining and Milling Company rehabilitated the 

property with a crew of 10 men and planned a 30–50 ton-per-day 

mill, but this operation was idled by the following year. There 

has been little activity at the property since the 1930’s, although 

some surface work was reported at the lower adit in 1988. 

Mountain View (Bonnie Anna) Mine

In 1904, the Mountain View mine, across the South Fork 

(reservoir) from the Franklin mine, was under development, and 

several shipments of high-grade ore were made. The following 

year, a new 10 stamp, 50 ton-per-day mill was built by the Provident Investment Company. The mill used electric power generated at Lime Creek. The mill shut down after a short time 

because of a lack of ore, however a new 1,500-foot-long adit was 

started from just above mill level. In 1906, the mill burned 

down, but work continued on the adit. In 1919, the LeBarr mine 

(the Mountain View mine) was taken over by George R. Colvin 

of Spokane. The mine was developed by a long tunnel that supposedly missed the ore because of faulting. Colvin believed that 

the fissure was faulted off and could be reached by a 500-footlong tunnel from the main adit. He planned to process ore at the 

Franklin mill. In 1927, Omo Mines Corporation developed the 

Mountain View mine, and the S.E. Mining Company also 

worked at Pine. There is no more information about the Mountain View mine. According to the U.S. Bureau of Mines, production since 1902 has been minimal (51 ounces of gold and 19 

ounces of silver from 31 tons of ore).

Ballard (1928) said the production from the Mountain View 

mine was $5,500, mostly from gold. Major production was from 

the Big Vein that strikes N. 65° E. and dips 60° SE. The best ore 

was at the intersection of the Big Vein with a north-striking 

structure called the Little Vein. 

Skeleton Creek Mining District

The mines on Bear Creek in the Skeleton Creek mining 

district are accessible from the South Fork of the Boise River 

Road from Big Smoky Guard Station. In 1992 access was on a 

rough road west along Bear Creek to the El Oro, Red Horse, and 

other mines just south of the Red Horse, and a very rough road 

north from Bear Creek to the Tip Top mine.

According to the U.S. Bureau of Mines, the Red Horse 

mine produced 1,118 ounces of gold and 544 ounces of silver 

from 302 tons of ore from 1902 to date. El Oro mine, the largest 

mine in the area, produced 4,776 ounces of gold, 2,492 ounces 

of silver, and some copper and lead from 10,841 tons of ore. 

The Tip Top and Bear Creek mines have had only minimal production, less than 100 ounces of gold each. Other mines in the 

district that have had production were not visited during this 

survey and are not shown in figure 24. These include the Old 

Sam mine, 1.5 mi northeast of Newsome Peak, the Jolly Roger 

claims between the El Oro and Red Horse mines (just south of 

Bear Creek), and the Gold Mountain mine (Remington and 

other claims), 2 mi southwest of the Red Horse. These properties are described by Federspiel and others (1992).

The Red Horse mine is astride the Willow Creek-Bear 

Creek fault. The El Oro mine is on the south side of the fault, 

and the Tip Top mine is about 1.2 mi north of the fault. Most of 

the mines in this area are in shear zones parallel with Bear 

Creek in granodiorite and are associated with northeast trending 

Tertiary dikes.

In 1901, Robert Chattin, Martin King, and others made the 

initial discovery of ore on Skeleton Creek in the vicinity of the 

Red Horse mine. In 1903, Chattin ran a test batch of ore mined 

from a shear zone in granite and dikes through his mill at Pine. 

By the following year, the Red Horse group (known as the Chattin mine) had several hundred feet of workings on a fissure vein 

in granite. There was little further work until 1981, when a twoman crew added 70–80 ft of drift to the 800-foot-long adit at the 

mine. The Galey Construction Company opened the mine the 

following year but dropped the property after a disappointing 

exploration program. 

In 1904 a new 700-foot-long tunnel was started at the Old 

Sam or Turner mine that had been previously developed by a 

230-foot-long tunnel. The Frazier mine (owned by the Drake 

Mines Development Company of Chicago) was being developed, and the Nellie F. and Mary Glen were worked by Lincoln, 

Nebraska interests. 

In 1907, the Frazier mine was incorporated as the El Oro 

Gold Mining and Milling Company by Erv Johnson, who 

planned on building a 10-stamp mill. According to Federspiel 

and others (1992), “The mine operated seasonally and intermittently from 1911 to 1942.” Underground development consists 

of about 8,000 feet of crosscuts, drifts, and raises on three levels 

(Idaho State Mine Inspector’s Report, 1937, p. 139). Workings 

are now inaccessible due to caving. A 30-ton per day, gravity 

reduction mill was erected about 1930 and was powered by a 
31

pelto wheel driven by water diverted from Bear Creek by a ditch 

situated along the north side of Bear Creek Canyon. The mill 

was converted in the 1930’s to steam power and a flotation 

recovery process. Ore was transported to the mill by an aerial 

tramway from mine level 2. Fire destroyed the mill in the late 

1940’s. Some work was reported at the El Oro mine in 1981 and 

1988 (Idaho State Mine Inspector).

In 1939, E.G. Platt and Aaron G. Carlson of Montana, representing Gold Hill Mining Corporation, did some development 

work at a quartz mine on Skeleton Creek. The mine had a 25 

ton-per-day mill.

Featherville Mining District

Placer mining is an important part of the mining history in 

the study area. The largest operation in the area was the South 

Park Dredging Company which operated on the Feather River 

and on the South Fork of the Boise River near Featherville. 

Dredge spoils are obvious along the rivers and near the town, 

and part of the old dredge is sunk in a pond just east of the town. 

In 1919, the Hammon Company (named for W.P. Hammon) 

of California obtained 1,100 acres of placer ground on the 

Feather River and announced plans for a major gold dredging 

project. In 1921, the South Park Dredging Company completed 

a power line to Featherville and started construction of a large 

dredge at a cost of a half million dollars. The company began 

dredging on August 21, 1922. In 1923, the dredge processed 

gold worth $200,000. In 1924, the dredge treated 1.6 million 

cubic yards of gravel and, with a capacity of 4,000 yards per 

day, was one of the largest gold dredges in Idaho. The 520 

horsepower electric Yuba dredge had 67 9-ft3 buckets that 

weighed 2,000 lbs each. The hull was built of Oregon fir; it was 

105 ft long with a 44 ft 7 in. beam and drew 7 ft of water. The 

digging ladder was 75 ft long and weighed 50 tons. The tailing 

stacker was 124 ft long. Twenty men were employed to run the 

dredge plant, which was the largest gold producer in Idaho in 

1924, 1926, and 1927 and the second largest in 1923 and 1925. 

Operations were suspended in June 1928.

Although not as large as the South Park venture, there were 

other placer operations on the Feather River. The S.G. Brendel 

operated in 1938 and the Feather Placers from 1959 to 1961; 

total production of the two operations was 36,917 tons of gravel 

yielding 375 ounces of gold and 136 ounces of silver.

Rocky Bar Area (Rocky Bar, Spanish Town,

Bear Creek, and Red Warrior Mining Districts)

Anderson (1943) described the geology and ore deposits in 

the Rocky Bar area in detail. Readers are referred to this publication and to Ballard (1928) for an early history of the area. The 

following discussion updates Anderson’s work.

Production

Anderson (1943) noted that peak production from mines in 

the Rocky Bar area was from 1875 to 1885 and had all but 

ceased in the next decade. Ballard (1928) estimated production 

from discovery to 1881 as $5,380,000 from lodes and 

$2,000,000 from placers. The U.S. Bureau of Mines noted 

minimal production from 1902 to date (table 2).

Table 2. Gold and silver production from mines in the Rocky Bar area, Idaho, 1902–present. 

[Compiled from U.S. Bureau of Mines unpublished production figures]

Property Tons

of Ore

Gold

(ounces)

Silver

(ounces)

Years of 

Major Production

Independence 142 89 43 Unknown

Vibrator 150 75 40 Unknown

Vishnu 232 360 204 Unknown

Wide West 210 50 18 Unknown

Avalanche/Richmond 1,950 124 623 1939–1943

Clifton Bell 159 274 82 1904–1905

Hearts Content 100 4 8 1937

Morning Star 2,200 310 137 1932–1935

Mineral Deposits
32 Geology and Mineral Deposits of Part of the Western Half of the Hailey 1°×2° Quadrangle, Idaho

Geologic Setting

Mines in the Rocky Bar area account for most of the lode 

production discussed in this paper, most of which was occurred 

before 1900. The geology of all of the deposits is similar; fissures in granodiorite contain gold-bearing quartz veins. The area 

from Red Warrior Gulch to Spanish Town is now being actively 

explored for bulk minable gold deposits. 

The age of mineralization in Rocky Bar area has been 

argued over the years; geologists are divided as to whether the 

deposits formed in the Cretaceous, Paleocene, Eocene. The same 

arguments apply to the gold deposits in the Atlanta area. There 

are very few dikes of Eocene age in the Rocky Bar area. Recent 

Ar40/39 plateau dates (58–57 Ma) on sericite from mineralized 

samples from the Vishnu dump indicate a Paleocene age.

History

Readers are referred to Anderson (1943) and Ballard (1928) 

for a review of the early development and history of the mines in 

the Rocky Bar area. There has been very little significant work in 

the Rocky Bar area from 1943 to recent times. In 1986, a placer 

operator found several large blue-quartz cobbles containing thick 

bands of native gold in a test pit just west of the area. These samples are similar to the descriptions of ore mined at Rocky Bar 

before 1900 (Anderson, 1943). If the samples are typical, then 

the rich ore necessary to account for the early gold production in 

the district is believable, in spite of the lack of mineralized samples on the mine dumps today.

Marsh Creek Mine

The Marsh Creek mine, south of the Rocky Bar area shown 

on figure 24, is described in Ballard (1928). The principal working was a 400-foot-long adit that cut a large quartz vein about 30 

ft wide inside the adit. In 1941, Marsh Creek Mining Company 

patented two claims on Marsh Creek. About 30 ft of crosscut 

was done in 1944. In 1947, the total workings consisted of two 

tunnels (150 ft and 180 ft long). A sample of adularia collected 

at the mine by R.F. Sanford in 1987 gave an Ar40/Ar39 date of 

39.3 Ma that indicates an Eocene age for this deposit.

Prospects North of the Bonaparte Mine

The Bonaparte mine is described in Anderson (1943). In 

1986, trees about 8 in. in diameter were growing on the old 

dumps of the mine and there was no sign of recent activity. 

North of the mine, at the end of the mine road, two open adits 

appeared to be relatively recent, but no further information on the 

property was available.

Ophir Mine

In 1952, Western Mines Inc., rehabilitated 400 ft of tunnel 

and 200 ft of shaft at the Ophir group in Blakes Gulch north of 

Rocky Bar. Four men were employed. At the time, the property 

was developed by 5 tunnels (the longest was 500 ft long) and a 

300-foot-deep shaft. There was a mill at the site. All assets of 

Western Mines, Inc. were transferred to Western Consolidated 

Mines in April 1952. In 1954, Western Consolidated Mines, Inc., 

employed 7 men at the Ophir who completed 110 ft of drifting 

and 60 ft of crosscuts and made surface improvements. There 

was little work after this.

Other Occurrences in the Rocky Bar Area

In the early 1980’s, Galli Exploration optioned a large 

claim block in the Red Warrior, Rocky Bar, and Hardscrabble 

Gulch area. In 1986, the company drilled about 20 holes in 

Hardscrabble Gulch. Later that year, Royal Apex Silver, Inc., 

acquired Galli. In 1987, when Coeur d’Alene Mines Corporation merged with Royal Apex Silver, what was Galli Exploration 

was spun off as a separate company called GEXA Gold. An 

additional 26 reverse circulation holes totalling 7,450 ft were 

drilled in 1987 and 25 more holes were drilled in 1988. Most of 

this work was in Hardscrabble Gulch. Estimated reserves at this 

time were 275,000 tons of 0.037 ounces per ton gold in Hardscrabble Gulch and 313,000 tons of 0.046 ounces per ton gold in 

Wide West Gulch for a total of about 0.5 million ounces of gold. 

In 1989, GEXA signed an agreement with Newmont Exploration 

Limited to evaluate and develop the GEXA’s 179 claims in the 

Rocky Bar area. Newmont drilled 19 reverse circulation holes in 

1989, 30 holes in 1990, and 11 holes in 1991, including a deep 

hole at the Ophir mine. The drilling program increased both 

open-pit and underground reserves but not enough for Newmont’s needs and the property was returned to GEXA in 1991. 

Lime Creek Mining District

The Lime Creek mining district is an informal district, not 

listed in Ross (1941). It is near the junction of Hunter Creek and 

Hawk Gulch, about 2 mi south of Lime Creek. Access is by the 

Hunter Creek-Cow Creek dirt road from the Cow Creek Reservoir or by a rough road from Moores Spring to the Hunter Creek 

road.

All of the deposits in the district mines are located very 

close to the northeast-trending Moores Flat fault and are in 

quartz veins hosted in biotite granodiorite that was intruded by 

aplite and pegmatite dikes.

Work began at the President and Hawthorne claim groups in 

1903, a late discovery in this part of Idaho. Seven men worked at 

the President, and the Hawthorne was developed by a 200-ft-long 

tunnel. During the same time period, the Jingo and Hornet mines 

were operated by a Salt Lake City company with 10 men and the 

mines had 600 ft of workings on a fissure vein. By 1904, the 

President mine (operated by the Lime Creek Mining Company) 

was equipped with a 25-ton roller mill that processed some gold 

ore. Plans called for a 1,000-foot-long tunnel. A tunnel was 

started at the Hawthorne on a 350-foot-long vein. In 1907, some 

ore was shipped that had been stockpiled several years before at 

the Jingo and Hornet. There was little further activity in the district until 1933 when 153 tons of stockpiled ore was shipped 
33

from the Jingo mine; the ore yielded 190 ounces of gold and 997 

ounces of silver. About 22 tons of ore were mined the same year 

at the President by E.O. Binyon. There was no further record of 

work in the district until 1988 when MVC Resources drilled 

three holes totaling 1,500 ft near the Jingo, Hornet, and President mines. 

The U.S. Bureau of Mines lists production from the Jingo 

and Hornet mines from 1902 to date as 257 ounces of gold and 

1,537 ounces of silver from 211 tons of ore. 

Volcano Mining District

The heart of the Volcano district is about 5 mi south of 

Highway 20. Access is by dirt road from the highway. The 

major property in the district is the Blackstone mine. DeLong 

(1986) and Allen (1940, 1952) described the geology of the 

Blackstone and other mines in the district. 

From 1902 to the present, the Blackstone mine produced 

838 ounces of silver and unspecified amounts of lead and copper from 81 tons of ore; the Bowerman group produced 1,416 

ounces of silver from 41 tons of ore; and the Index group produced 240 ounces of silver from 60 tons of ore (U.S. Bureau of 

Mines). None of the mines produced more than a few ounces 

of gold. 

There are two types of ore deposits in the Volcano district 

(DeLong, 1986). The Revenue and similar mines are in goldbearing quartz veins in complex fracture zones, whereas the 

Blackstone mine is an epithermal to mesothermal silver telluride, base-metal, manganese oxide deposit. The Bowerman 

mine has characteristics of both types of deposits (DeLong, 

1986). Mineralized rock in the Blackstone open pit is a central 

stockwork hosted in granodiorite; disseminated mineralization 

is present outside the stockwork. Delong (1986) suggested that 

the gold veins and the stockwork may either be independent of 

each other or represent different levels of the same system. A 

number of rhyolite dikes strike east-west across the area and a 

typical pink granite (biotite granite) of probable Eocene age 

crops out near the mine. 

In 1914, a trial shipment of silver ore was made from the 

Bower prospect (Bowerman group?) near Hill City, and, in 

1915, some silver-gold ore was shipped. There is little record of 

further development until 1929 when Consolidated Mines Syndicate started driving a tunnel on the Revenue group. According 

to Bell (1930), the Revenue tunnel penetrated 400 ft of decomposed granite and crossed a series of aplite dikes in decomposed 

granite. A number of rhyolite dikes and an andesite dike were 

exposed in the tunnel. The tunnel was 1,400 ft long by 1931, 

when Consolidated completed an additional 165 ft of workings. There was little work in 1932, but a small section of tunnel 

was completed the following year. A 2,000-foot-long tunnel 

was started in 1936, and work continued sporadically at the 

mine through 1939. All activity ceased by 1942. In 1948, 

Apache Mines Company optioned the Blackstone, Volcano, 

Index group, Mammoth group, Middlesex group, Independence 

mine, Hoffman mine, and the Revenue mine. There is no record 

of any substantial development by this company. 

The Blackstone claims were located by J.J. Rich and J.H. 

Hawley in the 1890’s. According to Bell (1930), the deposit was 

a “sheared quartz fissure richly stained with manganese oxide 

and copper carbonate” and was developed by a 100-foot-long 

tunnel. In 1984, Circa, Inc., began small shipments of concentrates from a mill built at Mountain Home to process about 

10,000 tons of ore from the Blackstone open pit that had been 

mined since 1982. Circa optioned the mine from the Blackstone 

Mining Company. Five men were employed at the mill, and 

about $1 million was reportedly spent on the mine and mill. 

Hambro Resources optioned the property from Circa in 1985 

and drilled nine holes at the mine. Richwell Resources conducted more drilling in 1987 at the Blackstone and reportedly 

found mineralized rock outside of the pit area. The company 

announced plans for constructing a mill at Fairfield, and a 20-

ton-per-day pilot plant was reportedly tested in 1988. There has 

been no activity since then.

Dixie Mining District by Thomas M. Jacob

The location of the Dixie mining district is incorrectly 

shown on the mining district map of Idaho by Ross (1941) as on 

House Mountain; instead, it is just south of Anderson Ranch 

Dam. The approximately 6 mi2 area that contains the district is 

easily accessible by paved road from U.S. Highway 20 by taking 

the Anderson Ranch Dam turnoff. The dumps of the King shaft 

are visible from this road across from the borrow pit from which 

fill for the dam was quarried. A cross section of the mine workings accessed by the King shaft is shown in figure 26.

Geologic Setting

Granodiorite of the Idaho batholith is the host rock for the 

abundant quartz veins in the Dixie district. The district is characterized by an abnormally high concentration of aplite and pegmatite dikes and by severe deformation, similar to the Anderson 

Ranch Dam area. Granitic rocks exhibit pervasive argillic and 

sericitic alteration. A number of dacite and rhyodacite dikes are 

in the area, and a rhyolite dike or small stock is exposed in the 

hill just west of the King shaft. Mineralization is milkey white 

quartz veins. Free gold was reported in the upper workings, but 

primary sulfide minerals including pyrite, galena, sphalerite, 

chalcopyrite, and molybdenite were encountered below 300 ft. 

Fluorite was observed on the mine dumps.

History and Production

The initial discovery of mineralized rock in the Dixie district is not documented but probably coincided with staking of 

the first claims. An anonymous 1933 report (perhaps authored 

by a mine shareholder) indicates that three claims were located 

in 1891 by Daniel H. Reber and two partners. These were the 

original King claim, site of the King shaft, and King vein, the 

major prospect and ore zone, respectively, of the district. Reber 

soon bought out his partners and remained the prominent mine 

developer until his death in 1929.

Mineral Deposits
34 Geology and Mineral Deposits of Part of the Western Half of the Hailey 1°×2° Quadrangle, Idaho

0 100

0

100

FEET

FEET

UNDERGROUND WORKINGS

KING "B" (KING SHAFT)

DALEY CONSOLIDATED MINING COMPANY

DRAWN BY R. N. ANDERSON

MARCH, 1935 AND FEBRUARY, 1961

MODIFIED BY T. M. JACOB 1985

40 FOOT LEVEL

100 FOOT LEVEL

100 FOOT LEVEL

150 FOOT LEVEL

150 FOOT LEVEL

250 FOOT LEVEL

250 FOOT LEVEL

300 FOOT LEVEL

300 FOOT LEVEL

150' Winze

400 FOOT LEVEL

450 FOOT LEVEL

192' West 426' East

390' West 580' East

168' West

312' East

172' West 150' East

HANGING WALL

HANGING WALL

HANGING WALL

HANGING WALL

HANGING WALL

HANGING WALL NOT DEFINITE

FOOT WALL

FOOT WALL

FOOT WALL

FOOT WALL

FOOT WALL

FOOT WALL

FOOT WALL

SIDE ELEVATION

PLAN

END ELEVATION

$10 Values

0.50 oz

12" wide $35

1.75 oz Water Level (1942)

18 oz Au pocket

Caved

Dump

Old mill and bins

100'

150'

250'

300'

400'

450'

485'

Top of

sulphide

ore zone

2' at $75 3.75 oz

balance 12" at

$30 1.5 oz

2 car loads mined here

assayed 3.25 oz/ton

Assays from last work

ran 1.6 oz/ton

4700' drain tunnel

to Rex millsite

400'

Winze caved

WINZE

FALSE FOOT

WALL

BLACK SCHIST

Figure 26. Mine workings of the King shaft in the Dixie district, Idaho. Modified from drawings by R.N. Anderson (March 1935 and February 1961), 

modified by T.M. Jacob (1985).
35

Newspaper accounts of activity in the district date as early

as July 24, 1892, when “remarkably rich finds” were reported by

several miners prospecting in the hills near the Dixie stage station. The Eddy mine, about 2 mi west of the station, was excavated to a depth of 60 ft; the face displayed a vein of ore 34 in.

wide and assayed as much as $1,128 per ton in gold (at $20 per

ounce). The Twin Hills mine consisted of two shafts exposing a

vein of quartz 8 ft thick that averaged approximately $30 per ton

in gold. Gold nuggets as large as a pea were reported as common in the vein of the Lone Jack mine. The Gold King mine,

located on the King claims, was developed by a winze sunk

along a vein of “very rich quartz.” Identification of these various

prospects, except for the Gold King mine (King shaft), is now

uncertain.

A 5-stamp mill was constructed at the Eddy mine and

began operation July 7, 1893. In 1894, a boarding house and

store were erected to serve approximately 40 men employed in

the mines. Daniel Reber sold a half interest in the mill and five

mining claims for $50,000, reinvesting the money in lumber and

mining equipment, and doubling the stamp capacity of the mill.

Reber reportedly deposited 200 ounces of gold in the Salt Lake

City mint during October 1895, the results of a 15-day mill run.

Difficulty in ore beneficiation became apparent in 1895

when roasting pans and furnaces were ordered for the mill.

Mining was probably progressing below an upper oxide ore

zone containing abundant free gold into a zone where the gold

was intimately associated with sulfide minerals.

In 1896, the Gold King mine was incorporated as Golden

King Mining and Milling Company with capital of $1,000,000

and holdings of 13 claims. New hoisting equipment was erected

at the King shaft, and a pump was installed for dewatering.

Early in 1897, the shaft reached a depth of 250 ft and there were

numerous drifts and crosscuts. The stamp mill proved totally

unsatisfactory for processing the ore, and in 1898 a 25 ton-perday capacity cyanide reduction plant was installed. Milling of

1,700 tons of ore from the 150-foot level indicated a recovery

rate of approximately 60 percent with returns of $6.50 per ton.

Difficulties encountered late that year due to inadequate crushing in the ball mill eventually resulted in abandonment of the

cyanide mill. In 1899, the property was reorganized as Crown

Point Mining Company.

During 1900 as many as 22 men were employed in the

King shaft, which was then 300 ft deep and exposed an ore zone

16 ft wide. An 8-foot thickness of footwall ore averaged $16 per

ton and an 8-foot thickness of hanging wall ore averaged $4-$7

per ton. Late that year the ore zone was delineated as 212 ft

long, ranging along strike from 6 to12 feet in thickness and

assaying from $28 to $200 per ton. By 1901, approximately

2,350 ft of drifts and crosscuts had been developed. A brief tonnage report by Boise, Idaho, metallurgist J. A. Pack dated “prior

to 1902” (probably early 1901) outlined proven ore from the

250-300 foot levels and estimated ore reserves from the 300-350

foot levels (table 3). Pack also estimated the tonnage of ore previously mined from the surface to the 250-foot level. Ore mined

until that time was reported to be in an oxide zone; primary sulfides were encountered only after work had extended below 315

ft.

A lease for continued work on the King shaft was granted

in 1901. Contrary to that agreement a winze was sunk from a

crosscut on the 300-foot level just south of the shaft. After 70 ft

of unproductive development, the lease was transferred to

another party who extended the winze to the 400-foot level

where ore was encountered. Samples collected from a vein 18

in. wide averaged $150–$200 per ton in gold. Because of the

problems with the on-site mill, the ore was high-graded and

shipped to Salt Lake City, Utah, for smelting, netting $55 per

ton. In 1902, the upper part of the winze caved, exposing ore

that the former lessees had missed by only 5 ft. Three carloads

of ore were shipped and assayed as shown in table 4.

Crown Point Mining Company, apparently having absorbed

adjacent properties and extending the boundaries of their claim

group, now included 58 lode claims, placer claims, and a

millsite. The company developed plans contingent on financial

backing, to sink the King shaft to a depth of 600 ft, then drive a

long crosscut-drain tunnel from within the Boise River canyon

to intersect the shaft. Such a tunnel would eliminate the need

for hoisting ore and pumping water.

The State Mine Inspection’s report contains the first public

record of work in the Dixie mining district. Reference is made

to the Crown Point claims and to the plan of driving a crosscut

tunnel from the Boise River to intersect the King shaft at depth.

This crosscut-drain tunnel, called the Cumberland tunnel, was

Table 3. Tonnage and grade calculations for the King shaft, Dixie mining district, Idaho.

[Includes estimates of previously mined ore and reserves to a depth of 350 ft. From J.A. Pack report inferred to date from 1901]

Ore

category

Vertical

footage

Dimensions

(length height

thickness, in feet)

Ft

3

/

ton

Tonnage Price

per ton

Value

Mined 0–150 ? ? 10,000 $ 9 $ 90,000

Mined 150–250 410 100 7.5 14 21,964 $13 $285,532

Proved 250–350 410 50 7.5 13 11,287 $17 $201,059

Reserves 300–350 410 50 7.5 12 12,812 $22 $281,864

Total Value $858,455

Mineral Deposits
36 Geology and Mineral Deposits of Part of the Western Half of the Hailey 1°×2° Quadrangle, Idaho

begun in 1904. The Crown Point claims and Cumberland tunnel 

were apparently unrelated to the claim group containing the 

King shaft, which was idle at this time due to legal problems. 

Rather than trending south, directly toward the King shaft, the 

Cumberland tunnel was driven east, thus avoiding property 

under litigation. Postulated ore zones in the easterly direction 

were apparently inferred from surface exposures; the anticipated 

Cumberland vein was regarded as an eastern extension of the 

King vein and the Crown Point vein, a parallel system approximately 3,000 ft to the north.

By 1906, legal problems with the claim block containing 

the King shaft were resolved. Daniel Reber obtained a loan to 

redeem the property and in 1913 negotiated for control of the 

Crown Point claims and Cumberland tunnel. The Daley Consolidated Mining Company was formed, and work focused on the 

Cumberland tunnel.

The King shaft was reopened in 1917, a new shaft house 

erected, and new pumping equipment installed. Attempts to 

reopen the old winze, which had previously been developed to a 

depth of 450 ft, failed due to bad ground and it was abandoned. 

Six men were hired to continue the main shaft, which was in 

good ground, downward from the 300-foot level.

Poor segregation of ore from waste during early development of the mine permitted direct smelter shipment of material 

collected on the dumps in 1917 and again in 1920. Results of 

these shipments are shown in table 5.

An agreement was signed in 1919 whereby $50,000 was 

paid for stock interest in Daley Consolidated. Forty feet of new 

shaft was excavated, and 51 claims were surveyed for patent. 

The remaining money was allegedly squandered, work ceased, 

and no patents were granted. Underground workings then 

totaled approximately 4,500 ft, including the King shaft and 

adjacent winze, five intermediate levels, and the Cumberland 

tunnel (contemporary length unknown). Further development 

was sporadic and minimal, generally consisting only of assessment work. 

In 1925, the King shaft hoisting facilities burned and the 

shaft caved. In 1929, a quitclaim deed was issued to Idaho Delaware Mines Corporation, and Daniel Reber died while on a 

money-raising venture. William and Henry Green took control 

of the property under lease as the United Gold Mining Trust. 

Active operations resumed in 1932 with rehabilitation of buildings, installation of a new boiler, and miscellaneous improvements to the mine entrances and equipment.

In 1935, United Gold Mining Trust contracted Rex Anderson to restore the King shaft. Problems with caving and dewatering halted work at the 300-foot level, and efforts were shifted 

to the Cumberland tunnel. By 1940, the tunnel was driven an 

additional 180 ft. Dimensions of the Cumberland tunnel during 

development are unrecorded, but the tunnel is reported to have 

been driven a total of 1,860 ft, and the Cumberland vein is postulated to lie approximately 900 feet beyond that point. A blind 

ore body intersected at approximately 1,400 ft and 46 ft wide, 

and contained small stringers of sulfide ore assaying 1.2 ounces 

per ton gold and 6 ounces per ton silver.

In 1942, a range fire swept over the property destroying the 

old mill and outbuildings and all mining records contained 

therein, including the scant documentation of mining in the 

Dixie district. Also in 1942, the properties were deeded to Rex 

Anderson in lieu of payment for his work on the King shaft and 

Cumberland tunnel.

Construction of Anderson Ranch Dam was begun in 1941 

at a site 1.5 mi upstream from the Cumberland tunnel. Approximately 9 million cubic yards of highly altered granitic rock, 

Table 4. Assay results of ore mined in the King shaft winze, Dixie mining district, Idaho, near the 300-ft level in 1902.

Date Tonnage Gold

 (ounces per ton)

Silver

 (ounces per ton)

Lead

(percent)

Zinc

(percent)

Copper 

(percent)

1902 19 1.6 6.5 6.3 3.2 —

1902 36 3.1 4.2 3.5 — —

1902 22 3.2 7.1 8.5 4.5 1.1

Table 5. Assay results of material gleaned from the dumps of the King shaft, Dixie mining district, Idaho, 1917 and 1920. 

[Leaders (—) indicate no data]

Date Tonnage Gold

(ounces per ton) 

Silver

(ounces per ton)

Lead

(percent)

Zinc

(percent)

Copper

(percent)

1917 14 1.27 4.73 4.50 4.30 0.82

1917 16 1.39 4.70 4.60 — 0.88

1920 2 cars 2.55 4.55 6.01 9.68 1.31
37

obtained from pits located east of Dixie Creek on Daley Consolidated claims, was used in the project. At completion in 1950, 

the Anderson Ranch Dam was the world’s highest earthfill dam 

(456 ft).

Daley Consolidated Mines granted a lease to Index-Daley 

Mines Company for construction of the Anderson drain tunnel 

in 1952. From a point just west of the Cumberland tunnel, a 

crosscut 4,800 ft long was constructed. Unlike the Cumberland 

tunnel, the Anderson drain tunnel trends directly beneath the 

King shaft workings. Upon completion of the crosscut, a raise 

was constructed that eventually intersected the King shaft winze 

at the 450-foot level. No ore was shipped, and, for reasons 

unspecified, operations were discontinued. The mine has been 

idle since 1955, and only the first 960 ft of the Anderson drain 

tunnel are accessible. The U.S. Bureau of Mines reports that 

some gold ore was shipped by Index-Daley Mines Company to 

Midvale, Utah, in 1956.

In the early 1960’s, Rex Anderson was granted patent for 

two millsites along the Boise River and for the King B lode 

claim. Daley Consolidated Mines Company currently consists 

of 58 claims, including the patented claims. 

Other Mines In or Near the Dixie Mining District

The only description of other mines in the Dixie district is 

a mention by the Idaho State Mine Inspector in 1905 that the 

Gold Pan claims, owned by the North American Exploration 

Company and on Big Water Creek above Baskams ranch, were 

being developed. A 110-foot-long tunnel was being driven on a 

quartz vein.

Roaring River Mining District

Two molybdenum deposits on Roaring River, the DeckerHortenstine and the Rinebold, were described by Schrader 

(1924). The molybdenum is hosted in quartz veins and in Tertiary granite of the Sheep Creek batholith. There has been no 

work on the deposits since Schrader’s report. Bennett (1980) 

noted that Tertiary granite in Idaho contains a high background 

amounts of molybdenum, and this is true for the Sheep Creek 

batholith. During a reconnaissance geochemical study of the 

area, Bennett noted that 84 percent of stream samples considered anomalous in molybdenum (equal to or greater than 3 ppm) 

were collected from stream segments draining the batholith. In 

1981, Inspiration Resources staked a large claim block that covered most of the Sheep Creek batholith. The company was 

rumored to be interested in molybdenum, uranium, and possibly 

tin in the granite. Little work was done to evaluate the area and 

the claims were dropped. 

Other Mines in the Study Area

Over the years, the U.S. Bureau of Mines and Idaho State 

Mine Inspector have noted small mines or prospects that were 

active in the study area (fig. 24).

•In 1904, several discoveries were made on Moores Flat or 

nearby and were developed. One of these, the Highland 

Mary, was worked in 1905 by seven men. Southwest of 

the Highland Mary, the Copper King group was being 

developed on Wood Creek at the same time. The Copper 

King property was in granite that contained porphyry 

dikes.

•In 1906, the Cat Creek mine was developed on a fissure in the 

upper drainage of Cat Creek a few miles east of Dixie.

•In 1921, a test shipment of rich silver ore was mined from the 

Worlds Fair mine near Mountain Home.

• From 1938 to 1940, Charlie Ford, Joe Babington, and John 

May developed the Mountain View tungsten mine, 3 mi 

from Corral.

•In 1938, the Sheep Creek Mining Corporation operated a placer 

mine northeast of Twin Springs. President and manager 

was John J. Kinsella.

•In 1941, Boise King Placers began operating a 7.5 ft3 bucketline dredge at Twin Springs. The operation employed 27 

men in 1942 but had shut down by the next year. Prior to 

this venture, a hydraulic placer on the Sun Flower claims 

(J.D. McGinnis) recovered 141 ounces of gold from 

42,650 yards of terrace gravels from 1934 to 1941. 

•In 1947, Herman Miller staked claims on an antimony prospect 

on the East Fork of Swanholm Creek. Later in the year, the 

Hermada Mining Company was formed. The vein was first 

worked in short adits and later from an open pit. The mine, 

described by Popoff (1953), is unusual because it contains 

an abundance of stibnite and no precious metals. Total 

production according to Popoff was 643 tons of antimony 

extracted from 5,048 tons of ore from 1947 to 1950. The 

ore was treated at a mill at Atlanta owned by Talache 

Mines, Inc. The stibnite is in quartz veins in north-northwest-trending fractures in the batholith. These structures 

are parallel with the Deer Park fault, which is about a mile 

west of the mine. An Ar40/Ar39 date of 61 Ma indicates 

that this deposit is Paleocene.

References

Allen, R., 1940, Geology and ore deposits of the Volcano district, Elmore 

County, Idaho: Moscow, University of Idaho, unpublished M.S. 

thesis, 43 p. 

Allen, R., 1952, Geology and mineralization of the Volcano District, Elmore 

County, Idaho: Economic Geology, v. 47, no. 8, p. 815–821.

Anderson, A.L., 1934, A preliminary report on recent block faulting in 

Idaho: Northwest Science, v. 8., no. 2, p. 17–28.

Anderson, A.L., 1943, Geology of the gold bearing lodes of the Rocky Bar 

district Elmore County, Idaho: Idaho Bureau of Mines and Geology 

Pamphlet 65, 39 p.

Armstrong, R.L, Taubeneck, W.H., and Hales, P.O., 1977, Rb-Sr and K-Ar 

geochronometry of Mesozoic granitic rocks and their Sr isotopic 

composition, Oregon, Washington, and Idaho: Geological Society of 

America Bulletin, v. 88, p. 397–411.

Ballard, S.M., 1928, Geology and ore deposits of the Rocky Bar 

quadrangle, Idaho: Idaho Bureau of Mines and Geology Pamphlet 

26, p. 41.

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38 Geology and Mineral Deposits of Part of the Western Half of the Hailey 1°×2° Quadrangle, Idaho

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References