Happy Jack Mine 

White Canyon Area 

San Juan County, Utah

GEOLOGICAL SURVEY BULLETIN 1009-H

This report concerns work done on 

behalf of the U. S. Atomic Energy 

Commission and is published with 

the permission of the Commission

A CONTRIBUTION TO THE GEOLOGY OF URANIUM

GEOLOGY OF THE HAPPY JACK MINE, WHITE CANYON 

AREA, SAN JUAN COUNTY, UTAH

By ALBERT F. TRITES, JR., and RANDALL T. CHEW, III

ABSTRACT

The Happy Jack mine is in the White Canyon area, San Juan County, Utah. 

Production is from high-grade uranium deposits in the Shinarump conglomerate 

of Triassic age. The Shinarump strata range from 16% to 40 feet in thickness 

and the lower part of these beds fills an eastward-trending channel that is more 

than 750 feet wide and 10 feet deep.

The Shinarump conglomerate consists of beds of coarse- to fine-grained quartzose sandstone, conglomerate, siltstone, and claystone. Carbonized wood is 

abundant in these beds, and in the field it was classified as mineral charcoal and 

coal.

Channels within the Shinarump, cross-stratification, current lineation, and 

slumping and'compaction structures have been recognized in the mine. Steeply 

dipping fractures have dominant trends in four directions, N. 65° W.t N. 60° E., 

N. 85° E., and due north.

Uranium occurs as bedded deposits, as replacement bodies in accumulations 

of "trash," and as replacements of larger fragments of wood. An "ore shoot" 

is formed where the three types of uranium deposits occur together; these ore 

shoots appear to be elongate masses with sharp boundaries.

Uranium minerals include uraninite, sooty pitchblende(?), and the sulfates 

betazippeite, johannite, and uranopilite. Associated with the uraninite are the 

sulfide minerals covellite, bornite, chalcopyrite, and pyrite. Galena and sphalerite 

have been found in close association with uranium minerals.

The gangue minerals include limonite and hematite (present in most of the 

sandstone beds throughout the deposit), jarosite that impregnates much of the 

sandstone in the outer parts of the mine workings, gypsum that fills many of 

the fractures, and barite that impregnates the sandstone in at least one part 

of the mine. Secondary copper minerals, mainly copper sulfates, occur throughout 

the mine, but' are most abundant in the outermost 30 feet of the workings. The 

bulk of the country rock consists of quartz and feldspar, and clay minerals.

The amount of uranium minerals deposited in a sandstone bed is believed to 

have been determined by the position of the bed in the channel, the permeability 

of the sandstone in the bed, and the amount of carbonized wood and plant remains 

within the bed. Not all of these features can be demonstrated in the Happy Jack 

mine itself. The beds considered most favorable for uranium deposition contain 

an abundance of claystone and siltstone both as matrix filling and as fragments.

Suggested exploration guides for uranium ore bodies include interbedded silt235
236 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

stone lenses, claystone and siltstone cement and pebbles, concentrations of 

"trash," covellite and bornite, chalcopyrite, and carbonized wood.

INTRODUCTION

SCOPE AND PURPOSE

The Happy Jack mine contains the largest known uranium deposit 

in the White Canyon area, San Juan County, Utah (fig. 38). A detailed study was started by the U. S. Geological Survey to determine

the mode of occurrence of the uranium minerals, and the structural 

and lithologic features useful as ore guides at the Happy Jack mine 

and elsewhere in the White Canyon area.

This report gives preliminary results of detailed mapping done 

during the 1952 field season, summarizes habits of the uranium deposits, and presents guides that may be useful in exploring for additional deposits. A map of the Happy Jack mine is shown in figure 39. 

The large-scale map (pis. 8, 9) of part of the mine was prepared 

by Trites and Renzetti from June 15 to July 4. Between August 7 

and October 2 Trites and Chew mapped the walls of about 750 feet 

of drifts in the northeast part of the mine on a scale of 1 inch = 5 feet. 

The fracture map (pi. 8) was prepared from the information on the 

wall maps by projecting all fractures to a waist-high datum plane.

The work described in this report was done on behalf of the Division 

of Raw Materials of the U. S. Atomic Energy Commission.

LOCATION

The Happy Jack mine is on the southwest rim above White Canyon 

in the western part of the White Canyon area, San Juan County, Utah.

The mine is about 15 miles by road east of Hite, Utah, and 75 miles 

west of Blanding, Utah (fig. 38) ; it is reached either from Hite or 

Blanding by Utah Highway 95, a- graded dirt road that connects 

Blanding with Hanksville, Utah.

PREVIOUS WORK

A report on the Happy Jack mine and the contiguous area has been 

written by Benson, Trites, Beroni, and Feeger (1952). Unpublished 

information concerning the mine and surrounding area has been furnished by the following geologists: B. P. Fischer and E. U. King

(1948), S. K. Smyth (1949), P. H. Dodd (1950), H. C. Granger and

E. P. Beroni (1950), J. W. Gruner and Lynn Gardiner (1950), and

L.J. Miller (1952).

MINE WORKINGS

Mine workings consist of slightly more than 3,000 feet of drifts 

and crosscuts. Four main adits have been driven into the hillside and
HAPPY JACK MINE, SAN JUAN COUNTY, UTAH 237

42°'

410-

114' 113 112

50

111° 110° 

100 Miles

109°

FIGURE 38. Index map showing location of the Happy Jack mine, San Juan County, Utah.

have been connected by crosscuts. About one-quarter of the mine has 

been mapped and is discussed in this paper.

GENERAL GEOLOGY

Rocks cropping out near the Happy Jack mine range from the 

Cutler formation of Permian age to the Kayenta formation of Jurassic (?) age and total more than 2,700 feet thick (see generalized section 

below). These beds are on the west flank of the Monument upwarp
238

EXPLANATION

v/////////////////////////////,.

Workings mapped in 

this report

°BC

Survey station

FIQDBB 39. Map of the Happy Jack mine showing the workings, July 1952.

that extends from northeastern Arizona to Elk Ridge in southeastern 

Utah near the northeastern corner of the White Canyon area. The 

fteds near the Happy Jack mine have a regional dip of 2°-3° SW. The

nearest exposures of igneous rocks are about 17 miles west of the

Happy Jack mine in the Henry Mountains.

Only the uppermost Moenkopi strata, the Shinarump conglomerate.

and the lowermost beds of the Chinle formation are described in detail in this report because only these three formations are present

in the immediate vicinity of the Happy Jack mine.
HAPPY JACK MINE, SAN JUAN COUNTY, UTAH 239

Generalized section of the rock formations near the Happy Jack mine, 

San Juan County, Utah

Age

sic).

Trlasslc (Early and

Middle Triassic).

Formation or member

Chinle formation: 

Upper member... ___ .

Unconformity

Unconformity

Organ Rock Tongue ....

Cedar Mesa sandstone 

member.

Thickness 

(feet)

200±........

300±... .....

107..........

304..........

224..........

0-40.. .......

195..........

306...-.. 

1,000 (estimated).

Description

Sandstone, dark-red, thin-bedded.

crossbedded. 

Sandstone, reddish-brown, thinbedded, calcareous; siltstone and 

mudstone. 

Mudstone and siltstone, variegated,

calcareous and bentonitic. 

Claystonc, gray and purple; sandstone

and conglomerate, gray to brown, 

lenticular.

fine-grained; conglomerate, orange; 

laminated siltstone and clay; lenticular.

Siltstone, dark reddish-brown to pale

red, laminated; shale, brown; sandstone, brown, fine-grained; and conglomerate.

Siltstone, reddish-brown, micaceous; 

and very fine-grained sandstone. 

Sandstone, cream-colored, crossbedded; 

shale, red, local, near top.

MOENKOPI FORMATION

In the White Canyon area the Moenkopi formation of early Triassic 

age is 195 feet thick and consists of interlayered beds of brown siltstone, fine-grained sandstone, and shale; locally, it has a bed of conglomerate at the base. The Moenkopi strata just beneath the Shinarump conglomerate consist of brown micaceous sandy siltstone that 

has been bleached to grayish green. This siltstone is laminated, the 

laminae averaging 3 mm thick.

The contact of the Moenkopi formation with the overlying Shinarump conglomerate is an erosional unconformity produced by the 

flowing water that deposited the sediments of the Shinarump conglomerate.

SHINARUMP CONGLOMERATE

In the White Canyon area the Shinarump conglomerate is discontinuous, occurring in lenticular beds that have exposures ranging 

from a few hundreds of feet to more than 5 miles in length. A section 

of the Shinarump as much as 40 feet thick may pinch out within a 

distance of 2,000 feet.

340735 55 2
240 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

The Shinarump strata at the Happy Jack mine are about 16 feet 

thick at the outcrop and thicken to 40 feet behind the rim. The outcrop of the Shinarump strata forms a ledge that extends y2 mile 

northwest and 1^4 miles southeast of the mine. Beyond these points 

the Shinarump pinches out.

The lower beds of the Shinarump conglomerate fill a channel more 

than 750 feet wide and 10 feet deep cut into the upper part of the 

Moenkopi formation. Diamond drilling by the U. S. Atomic Energy 

Commission indicates that the channel trends about due west but 

that the channel apparently bends rather abruptly beyond the southwestern limit of the underground workings and continues southwest. 

Diamond drilling further indicates that the channel is not well-defined, 

and that the bottom is marked by numerous scours.

Channels in the Shinarump are common within the mine and range 

from a few inches to 10 feet in width. This channeling is indicated 

by the presence of pinched-out beds and of abrupt lithologic changes 

both laterally and vertically. Three channels have been mapped in 

the Shinarump rocks (pi. 8).

The Shinarump conglomerate is comprised of beds of coarse- to 

fine-grained quartzose sandstone, conglomerate, siltstone, and claystone. Many of the conglomerate beds grade laterally into coarsegrained sandstone; gradation also has been noted between beds of 

fine-grained sandstone and siltstone.

The sandstone beds range from 1 to 100 feet in length and from a 

few inches to 4 feet in thickness. A large number of these beds have 

poorly developed internal stratification, the clarity of this stratification depending upon the type of cross bedding and the angle at which 

the unit has been transected by the mine working. Most of the 

stratified units are lenticular, although some tabular units are present. 

Nearly all of the units have erosional lower surfaces as described by

McKee and Weir (1953).

Structural features within the beds include cross-stratification and

contortion of the strata. Cross-stratification is very common in tke

sandstone beds; most of the sets of cross-strata have planar surfaces

of erosion as their lower bounding surfaces. These planar sets nave

resulted from beveling of the underlying beds and Subsequent deposition. Nearly all of tlie croSS-stratification sets are lenticular, that is, 

are bounded by converging surfaces, the lower of which are commonly

curved, Most Of the CrOSS-Strata arch downward and may be described as concave upward, The cross-strata in the part of the mine

mapped dip from less than 10° to more than 20° ; the general direction of dip is about N, OD° w, The dip of the cross-strata suggests that

the flow of streams here was from the southeast. Most of the crossstrata are termed high angle because the average maximum inclination 

is greater than 20° (McKee and Weir, 1953). Both medium-scale
HAPPY JACK MINE, SAN JUAN COUNTY, UTAH 241

and small-scale cross-stratification are present, but the medium-scale 

cross-strata, 1 to 10 feet in length, is more abundant.

Horizontal bedding is common only in sandstone beds and conglomeratic sandstone beds that immediately overlie siltstone beds in 

the lower part of the Shinarump conglomerate. These conglomeratic 

sandstone beds contain abundant interstitial clay and silt.

Many beds have been contorted by slumping that has resulted from 

the collapse of steep channel sides shortly after consolidation. Such 

slump features are especially common in fine-grained sandstone and 

siltstone beds where units as much as 1 foot thick have been distorted. 

A fault with reverse movement near station R. (pi. 9) has a displacement of 2 feet and is believed to have been caused by rupture and 

movement at the time the sediments were deposited. Current lineation was observed in the siltstone in the-channel crossing the drift 

near station 0. .....

The sandstones are poorly sorted and consist predominantly of 

grains of quartz, from a trace to 5 percent microcline, and a trace of 

mafic accessory minerals. Mica seems to be absent in most of the 

sandstones although it is conspicuous in the sandstone of the Shinarump in most of the White Canyon area. The quartz grains range 

from angular to subangular, the degree of angularity depending 

largely upon the amount of authigenic quartz surrounding the original 

grains. The microcline grains are pale yellow to red, and are commonly subangular. The sandstone is cemented by. clay, iron oxides, 

and jarosite.

Larger granules and pebbles of quartz, quartzite, siltstone, and 

claystone comprise from 1 to more than 10 percent of many of the 

sandstone beds. The pebbles of quartz and quartzite are as much as 1 

inch in diameter and are commonly well-rounded. The siltstone and 

claystone pebbles are most abundant in the lower parts of the sandstone beds and are as much as 4 inches across.

Siltstone occurs in beds ranging from 1 to 4 feet thick and from 

10 to 100 feet in length; it is also in small stringers from one-eighth 

to one-half inch thick and from 1 to 6 feet long. The siltstones are 

gray, greenish-gray, yellow, pink, or combinations of these colors. 

Most of the siltstones are sandy, and many grade laterally into sandstones. Horizontal contacts, however, are very sharp and vertical 

gradations through large ranges in grain size have not been found.

The conglomerate occurs in poorly defined units that are lateral 

gradations of coarse-grained sandstone. The conglomerate consists 

largely of pebbles of siltstone and claystone with few pebbles of quartz 

and quartzite.

Carbonized wood is abundant in the Shinarump conglomerate. Two 

forms of carbonized woody material have been recognized, a soft black 

mineral charcoal and a vitreous coal. The wood occurs both as logs
242 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

and as accumulations of smaller fragments which have been called 

"trash deposits." These trash accumulations tend to be near the 

bottom of the sandstone beds, and commonly the contact between two 

cross-stratified beds will be marked by a thin trash deposit from 

less than 1 inch to 6 inches thick. Carbonized vegetal material is 

abundant as partings and fragments in many of the siltstone beds. 

The largest logs mapped are 2 to 3 feet long and 4 to 6 inches in 

diameter. Many of the logs have been replaced by sulfide minerals, 

pitchblende, hematite, limonite, and secondary copper minerals. 

Many smaller pieces of carbonized wood have been replaced by pyrite.

LOWER MEMBER OF THE CHINLE FORMATION

Thinly laminated beds of gray sandy claystone of the lower member of the Chinle formation overlie the Shinarump conglomerate at 

the Happy Jack mine. This member is about 225 feet thick, and contains several lenticular beds of sandstone. It is capped by a bed of 

resistant sandstone and conglomerate about 20 feet thick.

STRUCTURAL FEATURES

The rocks at the Happy Jack mine dip 2°-3° SW and have been cut 

by four sets of steeply dipping fractures. These fractures strike N. 

65° W., N. 60° E., N. 85° E., and due north (pi. 9), listed in order of 

decreasing prominence. Besides the reverse fault noted above, only 

one other fault, about 30 feet south of Station A, (pi. 9) has been 

mapped. This fault strikes N. 69° W., dips almost vertically, and has

had the north side apparently moved 1.7 feet westward relative to the 

south side. No vertical movement is apparent.

Some clay seams occurring at lithologic contacts are apparently abnormally thickened over very short distances and may have rolled 

up into thicker masses as a result of bedding-plane movement. Elsewhere along many of these contacts a finely divided clayey material, 

similar to fault gouge, has been observed. These features could be

the result of penecontemporaneous deformation similar to that described by Fairbridge (1946).

Many of the quartz and quartzite pebbles of the more conglomeratic

sandstones are fractured and are easily broken along the fracture

planes. This fracturing is not believed to have resulted entirely from 

blasting in the mine because the shattering is very unif orm and general

in distribution, and pebbles in the outcrop of the Shinarump have

also been fractured.

The relation of the fracturing to the ore deposits has not been determined, but the fracturing is believed to have occurred after ore 

deposition. The ore trends seem to have no relation to the fractures.
243

No fractures are filled with ore material although many fractures contain secondary sulfates and limonite, especially near the surface.

Early studies by the U. S. Geological Survey in the White Canyon 

area during 1951 suggested that fractures may have played a dominant 

role in the emplacement of many of the uranium deposits (Benson, 

Trites, Beroni, and Feeger, 1952, p. 6 and 8). The present study shows 

no such structural control of the ore deposits in the Happy Jack mine.

URANIUM DEPOSITS

MODE OF OCCURRENCE

The uranium in the Happy Jack mine occurs as bedded deposits, 

as replacements of "trash" accumulations, and as replacements of 

larger wood fragments.

The bedded deposits occur in siltstone beds and along the contacts 

between sandstone beds and between beds of sandstone and siltstone. 

Uranium minerals extend upward into the crossbeds of some of the 

sandstone above these deposits. The bedded deposits range from a 

knife-edge to more than 1 foot in thickness.

Emplacement of "trash" accumulations is one of the most widespread 

occurrences of uranium in the mine; about 40 to 50 percent of the 

trash has been replaced by uranium and copper minerals in the part 

of the mine studied. The replaced material appears to have been small 

wood fragments, other plant remains, and organic material consisting 

of fragments too small to identify. Deposits of this type range from 

a fraction of an inch to 3 feet thick. Some of these areas also contain 

coal seams, but replacement of the coal appears to have been negligible.

Wood fragments are replaced by uranium and copper minerals near 

uraniferous areas. The largest replaced wood fragment found so far 

is about 3l/2 feet long and 3 inches in diameter. Wood more than 2 or 

3 feet from uraniferous areas is replaced by iron oxides or altered 

to charcoal.

MINERALOGY

The principal uranium mineral at the Happy Jack mine is pitchblende. Some of the pitchblende is of such high specific gravity (9.1) 

and such purity (greater than 90 percent U02 ) that, according to 

A. D. Weeks (written communication, 1952) it should be called uraninite. This uraninite has replaced plant remains, larger fragments of 

wood, and seams and pebbles of claystone and siltstone. In places the 

uraninite partly fills the interstices between quartz grains and fills 

microscopic fractures cutting the grains.

A soft black material believed to be sooty pitchblende is contained 

in many of the bodies of uraninite. Also closely associated with the 

uraninite, and commonly deposited on the mine walls, are the uran-
244 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

iferous sulfates betazippeite, johannite, and uranopilite (Weeks and 

Thompson, 1954).

Sulfide minerals are closely associated with the uraninite. Pods 

of the most radioactive material commonly contain abundant covellite 

and minor bornite. Chalcopyrite, pyrite, bornite, and covellite have 

replaced wood fragments and impregnated sandstone beds adjacent 

to uraniferous material. Many fragments of charcoal and seams of 

carbonaceous claystone and siltstone that have been replaced by uraninite are rimmed by concentrated impregnations of chalcopyrite in the 

sandstone. Chalcopyrite also occurs in stringers and small masses 

and blebs in siltstone above or below uraniferous sandstone.

Galena has been found in the southeastern part of the mine workings where it has impregnated sandstone containing abundant uraninite replacements of plant fragments. Sphalerite has also impregnated the sandstone in the same area, but is associated with charcoal 

that has not been replaced by uraninite.

Secondary quartz has been a'dded as overgrowths on the detrital 

quartz grains of many of the more coarse-grained sandstones. This 

authigenic quartz forms crystal faces on many of the grains.

In addition to the quartz, clay minerals, and feldspar contained in 

the ore-bearing sandstone, the principal gangue minerals are chalcedony, limonite, hematite, gypsum, jarosite, and minor barite.

Limonite occurs in many of the sandstone beds, especially in the 

more oxidized parts of the mine. Zones of limonite, such as are 

found in the eastern part of the mine workings, surround zones of 

sulfide minerals and may indicate the boundary of the ore body. The 

limonite, much of which has been identified as goethite by T. G. Lovering (oral communication, 1953), occurs as impregnations in sandstone, as replacements of plant remains and larger pieces of wood, as 

impregnations and replacements of claystone and siltstone seams and 

fragments, and as fillings of many of the fractures. Limonite impregnations in sandstone beds range from sparsely distributed spots, 0.2 to 

2 mm across, to strongly concentrated impregnations from less than 

1 inch to 1 foot thick. Strongly concentrated limonite impregnation

zones occur around many of the plant remains, larger pieces of wood,

and claystone and siltstone seams that have been replaced by uraninite 

and sulfide minerals. Some of the more heavily concentrated limonite 

impregnating sandstone is abnormally radioactive; much of this radioactivity is believed to be due to disintegration products from the radioactive decay of uranium.

In the oxidized part of the mine hematite has replaced some of the 

larger wood fragments where it is associated with limonite and secondary copper minerals.

Locally chalcedony has cemented the quartz and feldspar grains of
HAPPY JACK MINE, SAN JUAN COUNTY, UTAH 245

some of the sandstone beds. Some of the chalcedony is in fibers that 

are in parallel orientation over areas as much as 2 inches across.

Some of the fractures cutting Moenkopi and Shinarump strata are 

filled with gypsum which is believed to have impregnated the sandstone adacent to sulfide bodies in the more oxidized parts of the mine.

Locally jarosite has impregnated the sandstone beds in the mine and 

seems to be associated with carbonaceous material.

Barite is rare in the Happy Jack mine, but in the southeastern part 

of the mine white tabular crystals, 1 mm long, have been found associated with sphalerite that has replaced carbonized wood.

Secondary copper minerals, mostly the hydrous copper sulfates, 

occur mainly in the outer 30 feet of the mine, but have been found as 

much as 250 feet behind the portals. A small amount of malachite 

has been found near the surface. These minerals have impregnated 

the sandstone beds, siltstone and claystone seams and pebbles, and 

replaced larger wood fragments.

LOCALIZATION

Apparently most of the uraninite has been localized by sedimentary 

features. Localization by megascopic structural features cannot be 

shown, although uraninite locally has filled fractures in quartz grains; 

bedding-plane movement, by fracturing the rocks and increasing their 

permeability, is a possible structural control but the existence of such 

movement has not been proved.

The amount of uranium contained in a sandstone bed is believed to 

depend mainly upon the position of the bed in the channel, the 

permeability of the sandstone, and the amount of carbonized wood and 

plant remains within the bed.

Most of the uranium deposits in the White Canyon area, as at the 

Happy Jack mine, are in the lower sandstone or conglomerate beds 

of the Shinarump conglomerate. Most of these ore-bearing sandstone 

and conglomerate beds immediately overlie impermeable siltstone beds 

of either the Moenkopi formation or the Shinarump conglomerate. 

This circumstance is believed to be the most important factor in the 

localization of the uranium ore deposits. These ore-bearing sandstone 

beds are believed to have been rather flat tabular conduits through 

which subsurface solutions migrated. Whether solution movements 

along these conduits took place above or below the water table has not 

been determined, but if the uranium deposition was of early Tertiary 

age, several thousands of feet of overlying sediments of Jurassic and 

Cretaceous ages may have been present when the minerals were deposited. The solution flow seems to have been similar to groundwater 

movement but the reduced state of the iron as the sulfide suggests 

that reducing conditions were present instead of oxidizing conditions 

that are prevalent in most ground-water circuits. The amount of
246 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

carbonaceous material in these beds is believed to be insufficient to 

maintain a reducing environment for the great volume of solutions 

that must have migrated and deposited the sulfide minerals, and it is 

believed that the solutions themselves must have been reducing in 

nature. Solution movement is known to be possible below the water 

table (Tolman, 1937, p. 305-307). Water, flowage below the water 

table has occurred.in many mines, and deep wells have brought forth 

artesian flow from aquifers far below the present water table. Flow 

of this type might well explain the unoxidized condition of the ore 

deposits. The underlying impermeable beds would suggest a perched 

subsurface flow, and siltstone beds locally overlying the ore-bearing 

sandstone may have acted further to confine the solutions to the 

sandstone.

The grade of the uranium deposits seems to be independent of the 

thickness of the sandstone bed containing them. In the White Canyon 

area, the thickness of sandstone beds containing more than 0.20 percent UsOg is a few inches to 4 feet. Zones as much as 7 feet thick have 

been mined, but most of these are believed to be composed of two or 

more beds of ore-bearing sandstone. Deposits of this type have 

been found at the Happy Jack mine.

The permeability of the sandstone is believed to be the second important factor in determining the amount of uranium contained in 

a sandstone. Permeability conditions within the Shinammp strata 

are believed to range between extremely wide limits; siltstone beds 

probably are nearly impermeable, sandstone and conglomerate beds

containing significant amounts of clay and silt cement may be moderately permeable, and sandstone beds with little cement are probably

highly permeable. Most of the uranium deposits in the Happy Jack

mine occur in beds having the intermediate permeability; these beds 

contain abundant seams and pebbles of claystone and siltstone and 

abundant claystone or siltstone cement. The amount of claystone

and siltstone in a sandstone bed is also dependent upon the lithology 

of the underlying bed; sandstone beds immediately overlying siltstone 

beds contain a greater abundance of clay and silt particles than sandstone beds overlying other sandstone beds. Perhaps the more permeable sandstone beds have had the uramferous solutions pass 

through them too rapidly to permit precipitation within them,

whereas the silty and clayey sandstones had a much slower solution 

movement allowing sufficient time for the deposition of uranium. 

Control of the ore deposits by the permeability of the beds is suggested in many of the deposits in the White Canyon area, but is not 

clearly seen at the Happy Jack mine.

Carbonized wood and plant remains are believed to be less important than position or permeability in determining the total amount
HAPPY JACK MINE, SAN JTJAN COUNTY, UTAH 247

of uranium deposited in a sandstone bed, but are believed to localize 

the uranium within the bed. Sandstone beds containing significant 

amounts of carbonized vegetal material also tend to contain abundant 

claystone and siltstone cement and fragments. Carbonized wood is 

replaced in areas of abundant uraninite, and trash accumulations 

form the center of most uranium mineral concentrations that grade 

out into and impregnate the host rock. In beds containing relatively 

small amounts of uranium minerals, the trash lenses contain most 

of the uranium, and the host rock is apparently barren. The carbonaceous material near the base of some sandstone beds has associated 

sulfide and uranium minerals, whereas similar material higher in 

the bed is barren of such minerals.

Locally the three types of deposits bedded, trash replacement, and 

wood replacement occurring in close proximity form definite areas 

or "ore shoots" of high-grade uranium ore. These ore shoots in many 

places have sharp borders, and appear to be elongated. The best 

evidence for this is in the drift between stations A and C (pi. 8). 

A narrow band of sulfide and limonite concentration can be traced 

along the walls for most of the distance between E and O. The face 

at C contains an irregular lenticular area, about 6 feet wide and 4 feet 

thick, of concentrated sulfide minerals. The area is highly radioactive. The drift is believed to have been driven along an ore shoot 

that trends approximately parallel to the drift. This belief is supported by the rapid decrease in radioactivity in drifts B-D and E-F.

ORE GUIDES

Guides believed to be useful for exploration for uranium ore bodies 

in the Happy Jack mine area, in order of importance, are as follows:

1. Interbedded siltstone lenses. Uranium ore is apparently concentrated in the lower parts of sandstone beds overlying this type of 

lens. The Shinarump conglomerate contains several of these lenses, 

one above the other, separated by sandstone. At least three of these 

lenses have been exposed in the mine workings. Drifts floored in 

the Moenkopi formation should be driven with the idea in mind 

that ore can occur anywhere, vertically, in the lower part of the 

Shinarump conglomerate. The back of the drift should be explored 

at intervals close enough together to determine the presence or absence 

of siltstone lenses overhead.

2. Presence of claystone and siltstone as cement, seams, and pebbles. 

This type of lithology is favorable for uranium occurrence in sandstones immediately overlying lenses of siltstone.

3. Presence of concentrations of carbonaceous trash in sandstone.

4. Presence of covellite, either massive or disseminated, in the
248 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

sandstone. A similar occurrence of bornite is favorable, but covellite 

is believed to be a better guide.

5. Presence of chalcopyrite. Chalcopyrite occurs everywhere 

in the ore zones but also occurs in high concentrations as much as 

40 feet from high-grade ore.

6. Presence of carbonized wood. Carbonized wood indicates favorable lithology, but in mineralized zones it is replaced by copper and 

uranium minerals.

LITERATURE CITED

Benson, W. E., Trites, A. F., Jr., Beroni, E. P., and Feeger, J. A., 1952, Preliminary report on the White Canyon area, San Juan County, Utah: U. S. Geol. 

Survey Circ. 217.

Fairbridge, R. W., 1946, Submarine slumping at the location of oil bodies: Am. 

Assoc. Petroleum Geology Bull., v. 30, p. 84-92.

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