A Comparison Among CaliperLog, Gamma-Ray-Log, and 

Other Diamond-Drill-Hole Data

GEOLOGICAL SURVEY BULLETIN 1052-G

This report concerns work done in cooperation with the U. S. Bureau of Mines 

on behalf of the U. S. Atomic Energy 

Commission and is published with the 

permission of the Commission

A Comparison Among CaliperLog, Gamma-Ray-Log, and 

Other Diamond-Drill-Hole Data

By C. M. BUNKER and H. C. HAMONTRE

EXPERIMENTAL AND THEORETICAL GEOPHYSICS

GEOLOGICAL SURVEY BULLETIN 10S2-G

This report concerns work done in cooperation with the U. S. Bureau of Mines 

on behalf of the U. S. Atomic Energy 

Commission and is published with the 

permission of the Commission

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1959
UNITED STATES DEPARTMENT OF THE INTERIOR 

FRED A. SEATON, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

The U. S. Geological Survey Library has cataloged this publication as follows;

Bunker, Carl Maurice, 1915-

A comparison among caliper-log, gamma-ray-log, and 

other diamond-drill-hole data, by C. M. Bunker and H. C. 

Hamontre. Washington, U. S. Govt. Print. Off., 1959.

iii, 241-255 p. map, diagr, tables. 25 cni. (U. S. Geological 

Survey. Bulletin 1052-G. Experimental and theoretical geophysics)

1. Borings. 2. Radioactivity Measurement. i. Hamontre, 

H. C., joint author, n. Title. (Series: U. S. Geological Survey. 

Bulletin 1052-G. Series: U. S. Geological Survey. Experimental 

and theoretical geophysics)

622.3493

For sale by the Superintendent of Documents, U. S. Government Printing Office 

Washington 25, D. C. - Price I5f (paper cover)
CONTENTS

Page

Abstract__________________________________________________._._ 241

Introduction._____________________________________________________ 241

Location.__-____--___---_____-__________-,__--_____-___________-- 242

Caliper logging____________-_-_____--______^..-___--_______--_____-_ 243

Equipment _-_-____--____-___________-__________-_____-__-__.._ 243

Procedure ___-____--____-____-_-_-___-___-__________-_-_____-_ 243

Results-..__.-_______-_-_-_______-_-__,_____..-____________ 245

Comparison of diameter with, percentage core recovery _____________ 246

Comparison of drill-hole diameter with rock type __________________ 247

Comparison of drill-hole diameter with equivalent UsOg content-____ 247

Comparison of core recovery with equivalent UsOg content---------- 247

Conclusions_ -___-_-__-____-________________.-_____-___---___---_ 248

ILLUSTRATIONS

FIGUBE 66. Index map of part of the Colorado Plateau showing the location of the Jo Dandy area, Montrose County, Colo_______ 242

67. Well-bore caliper in well________-__-_--____-_-_---_--_--_ 244

TABLES

TABLE 1. Relation between drill-hole diameter and core recovery.______ 246

2. Relation between drill-hole diameter and rock type and texture 247

3. Physical, geologic, and radioactivity data for six drill holes, Jo

Dandy area, Colorado.________-__--____-____-.._-_---_ 249

m

EXPERIMENTAL AND THEORETICAL GEOPHYSICS

A COMPARISON AMONG CALIPER-LOG, GAMMA-RAYLOG, AND OTHER DIAMOND-DRILL-HOLE DATA

By C. M. BUNKER and H. C. HAMONTRE*

ABSTRACT

To obtain comparative data on the variation in gamma-ray intensity accompanying possible variation in the diameter of small-diameter diamond-drill holes, 

six drill holes in the Jo Dandy area, Montrose County, Colo., were caliper logged 

using a well-bore caliper developed by the II. S. Bureau of Mines. The caliper 

logs show that within radioactive-ore zones the variation in drill-hole diameter 

is insufficient to cause significant variation in the gamma-ray logging measurement, that with increasing particle size in the ore-bearing sandstone the drillhole diameter tends to increase slightly, and that with increase in hole diameter 

the core recovery tends to decrease slightly.

INTRODUCTION

In the investigation of gamma-ray logs, particular emphasis has 

been placed on the calibration of the logs in terms of the thickness 

and grade of radioactive ores. One factor in such calibration is 

variation in drill-hole diameter. Controlled experimental gammaray logging measurements have shown that an increase in the diameter 

of a drill hole might either increase or decrease the measured radiation 

intensity, depending upon the geometry of a particular measurement. 

Thus, sufficient variation in the hole diameter where overbreaking, 

sloughing, or swelling has occurred in the drill hole might lead to 

erroneous estimation from the gamma-ray log of the thickness and 

grade of ore. Although few or no data existed on the variation of 

hole diameter in actual exploratory drilling for carnotite deposits in 

the Colorado Plateau region before the present study, overbreaking 

or sloughing of drill-hole walls was suspected to occur in the higher 

grade ore zones.

The need for caliper logs of drill holes has long been obvious, but 

the small diameter of the customary diamond-drill holes in the 

Colorado Plateau region most are AX and BX size has heretofore 

prevented such logging. Recently, a caliper designed to pass through 

a 2-inch ID pipe was developed by the U. S. Bureau of Mines. By 

cooperative agreement between the U. S. Bureau of Mines and the

*TJ. S. Bureau of Mines.

241
242 EXPERIMENTAL AND THEORETICAL GEOPHYSICS

U. S. Geological Survey, six selected drill holes were caliper logged 

in October 1953. This work was done on behalf of the Division of 

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

LOCATION

The drill holes (JD-327, JD-329, JD-339, JD-341, A, and B) are 

part of the Jo Dandy drilling project in Montrose County, Colo, the 

general area of which is shown on the index map (fig. 66). The first

Grand Junction^

Whitewg

Thompson

GRAND

\

MESA

O

ateway 

f\ '

iMoab

R 0 S

._.

La Sal Junction^

\

SAN J IT A N

/ I

Monticellol R ' i u

M I G U E L

0 L 0 R E S

J)ove Creek

20 Miles

FIGURE 66. Index map of part of the Colorado Plateau showing the location of the Jo Dandy area, Montrose

County, Colo.
CALIPER-LOG, GAMMA-RAY-LOG, OTHER DRILL-HOLE DATA 243

four holes were drilled by a contractor for the Geological Survey. 

Holes A and B were drilled by the Climax Uranium Co., Grand Junction, Colo.

CALIPER LOGGING

EQUIPMENT

The Bureau of Mines well-bore caliper was designed to provide an 

instrument that could pass through 2-inch tubing. It is suspended 

from a single-conductor armored electrical cable (Amergraph, type 

1-H-O). The instrument differs from other well-bore calipers in 

that it measures four equispaced radii of the hole with an accuracy of 

one-fourth inch. The measuring arms can be opened and closed 

when the instrument is at any depth in the well. The well-bore 

caliper is 1% inches in diameter and approximately 6 feet long. The 

measuring arms are forced outward simultaneously by an electrohydraulic system but move independently so that each arm can take 

any position to follow the shape of the well bore. Each arm is linked 

mechanically to a variable resistor so that the degree of arc of the 

arm can be measured with an ammeter at the surface. The ammeter 

is calibrated to read directly in inches the distance the arm tip is 

extended from the longitudinal axis of the probe. The position of 

each of the four arms is determined by using a mechanism to switch 

current through each resistor. The diameter of the drill hole is then 

determined by adding the readings from opposite arms.

Figure 67 shows the caliper probe and the auxiliary equipment 

used in making well-bore measurements. The caliper is lowered into 

the well on the cable from a reel mounted in a laboratory truck. A 

3-kilowatt 110-volt alternating-current generator supplies power for 

operation of the instrument. Contact between the control panel and 

the conductor of the cable is made through the hub of the cable reel 

by a slip-ring contact, giving the operator full control of the probe 

throughout the depth of the well, allowing him to open and close the 

measuring arms and observe the reading on the meter in the control 

panel.

The cable reel is driven by a gasoline engine which is coupled to the 

reel through a hydraulic drive in order to prevent overloading the 

cable if the instrument sticks in the hole while it is being withdrawn. 

A weight indicator shows the tension of the cable at all times. The 

cable runs through a depth indicator at the surface which indicates 

the depth of the caliper probe to within one-half foot.

PROCEDURE

The initial step in caliper logging is to turn on the electric current 

and to allow about 20 minutes for the warmup and stabilization of 

the electrical components in the circuit. To calibrate the caliper before
244 EXPERIMENTAL AND THEORETICAL GEOPHYSICS

1 CONTROL PANEL

2 CABLE REEL

3 CABLE

4 DEPTH INDICATOR

5 SWIVEL HEAD

6 WELLHEAD

7 TUBING

8 CALIPER PROBE

FIGURE 67. Well-bore caliper in well.
CALIPER-LOG, GAMMA-RAY-LOG, OTHER DRILL-HOLE DATA 245

logging, the measuring arms are expanded to the full open position 

(18 inches) and the measuring circuit is checked with a calibration 

ring of that diameter. When the measurements are correct at fully 

open and fully closed positions, the circuit has been stabilized and 

the instrument is ready for use. The measuring arms are closed, the 

probe is lowered to the bottom of the hole, and the measuring arms 

are reopened. Measurements are made at selected points as the wellbore caliper is drawn up. The instrument is suspended at each position at which a reading is made, and measurements are recorded for 

each of the four measuring arms. Depths at observation points in 

the hole are recorded, together with the corresponding well-bore 

measurements. A reading can be made, recorded, and the instrument moved to the next position in approximately 20 seconds when the 

depth increment is 1 foot or less.

The procedure in calipering the drill holes on the Colorado Plateau 

was to start approximately 10 feet below the ore body and log at 

1-foot increments up to the ore zone, at 6-inch increments through 

the ore zone, and at 1-foot increments for 10 feet above the ore. Some 

of the logs show the diameters to be smaller than the diameter of the 

drill for 3 or 4 feet (for example, JD-339, 681.0-684.0 ft; JD-341, 

173.0-175.0 ft). This is believed to have been caused by failure of the 

measuring arms to penetrate mud on the walls. Penetration could 

have been achieved by raising and lowering the instrument for a short 

distance after the arms were opened and before starting to log, but 

this was not done for fear of dislodging material from the walls and 

causing the instrument to jam. All holes were gamma-ray logged, 

then immediately caliper logged in order to determine the hole size 

when the gamma-ray log was made.

As this caliper probe is a prototype and the only one built before 

this work, maximum precaution was taken to prevent its loss. Badly 

caved holes in which there was chance of wedging the probe and losing 

it were not logged.

RESULTS

The data compiled for the 6 holes include the depth at which the 

various data were obtained; the average diameter of the hole determined by taking one-half the summation of the 4 radii; percentage 

core recovery; the percent equivalent U3O8 of the pulverized core; 

the percent chemical U3O8 of the pulverized core; the counts per 

minute derived from the core by a radiometric core scanner; the 

thickness and percent equivalent U3O8 for radioactive zones as determined from the gamma-ray log (Barnaby); and, the rock type 

and its texture. These are given in table 3.

484267 59 2
246 EXPERIMENTAL AND THEORETICAL GEOPHYSICS

COMPARISON OF DIAMETER WITH PERCENTAGE CORE 

RECOVERY

Analysis of the measurements of drill-hole diameter with the 

corresponding percentage core recovery shows only a slight tendency 

for the hole diameter to increase as the percentage of core recovery 

decreases. Table 1 shows the comparison of the measured drill-hole 

diameters with the corresponding percentage core recovery. Before 

the caliper measurements, it had been thought that factors causing 

low core recovery might also cause a corresponding increase in hole 

diameter.

TABLE 1. Relation between drill-hole diameter and core recovery

Drill hole

JD-327 

JD-329- ....

JD-339 

JD-341...... _

A... 

B._ ............

Diameter 

of bit 

(in.)

3.00 

2.32 

3.00 

3.00 

3.00 

2.32

Drill hole

JD-327....... . ..........

JD-329 . .. __ ....

JD-339. ..............

JD-341..................

A....... .............

B._ ..................

Avg 

diameter 

of hole 

(to.)

3.38 

3.26 

3.50 

3.59 

4.32 

4.45

Diameter 

of bit 

(in.)

3.00 

2.32 

3.00 

3.00 

3.00 

2.32

Drill-hole diameter (in.) where core recovered ' (percent) was 

7.5

3.46

Avg 

diameter 

of hole 

(to.)

3.38 

3.26 

3.60 

3.59 

4.32 

4.46

10

3.35

4.64 

4.34

20

3.69 

4.72

30

2.78

4.21 

4.11

44

3.19

46

2.88

48

3.26

60

6.60

Drill-hole diameter (in.) where core recovered ' 

(percent) was 

51

3.87

60

3.97

72

3.02

88

3.85

92

3.62

99

3.48

100

3.38

3.49 

3.48

' The percentage of core recovered is derived from the ratio of the length of the core recovered to the length 

of the run.

Causes of core loss include excessive bit pressure and drilling 

speed which in turn cause the rod to whip, thereby increasing the 

size of the drill hole by a reaming action. It was the observation 

of the Bureau of Mines engineer that the high-core-recovery holes 

JD-327 (NX bit) and JD-339 (NX bit) were drilled with a high 

drilling speed, a low bit pressure, and only slight visible whipping 

of the drill stem. Hole numbers JD-329 (BX bit) and JD-341 (NX 

bit) were drilled with greater pressure and low drilling speed. The 

drill stems were observed to be whipping to the extent that the core 

was probably broken and pulverized as it was cut. In addition, 

JD-329 and B were drilled with a smaller size bit (BX), which is 

 conducive to greater core loss.
CALEPER-LOG, GAMMA-RAY-LOG, OTHER DRILL-HOLE DATA 247

COMPARISON OF DRILL-HOLE DIAMETER WITH ROCK TYPE

The rock types penetrated by the six holes are sandstones of various 

grain size and mudstone. The ore zones are chiefly sandstone with 

carnotite as an interstitial material. The friability of the sandstone 

increases with increasing carnotite content. Kesults of previous 

drilling projects indicated that core loss through high-grade ore 

zones is occasionally serious; however, there was no appreciable core 

loss due to this cause in the six holes described here.

Analysis of the comparison between the measured drill-hole diameter 

and the corresponding rock type indicates that the drill-hole diameter 

increases with increasing gram size of the rock (table 2). This might 

well be expected as the abrasive action is reduced with a reduction 

in particle size.

TABLE 2. Relation between drill-hole diameter and rock type and texture

Drill hole

JD-327.. ___ 

JD-329__-_. __.____ 

JD-339.. ... ....--

JD-341 __ ..........

A..... ... ... ... ...

B..._ ....

Diameter of bit 

(in.)

3.00 

2.32 

3.00 

3.00 

3.00 

2.32

Avg diameter 

of hole 

(in.)

3.38 

3.26 

13.50 

«3.59 

4.32 

4.45

Sandstone

Drill-hole diameter (in.) where grain size was 

Fine to 

medium

3.56

Fine

3.52 

3.28

3.81

Fine to 

medium 

fine

3.41

3.52 

3.18

Fine to 

very fine

3.40

3.41

Very 

fine

3.37

Mudstone

3.14 

2.75 

3.24 

3.80

' Excluding bottom]4 feet, where arms of caliper were not fully extended to drill-hole wall.

COMPARISON OF DRILL-HOLE DIAMETER WITH EQUIVALENT

U3O8 CONTENT

Analysis of data in table 3 indicates lack of correlation between 

the measurements of drill-hole diameter and the corresponding 

UaOg content of the core samples. It is highly probable that there 

is an increase hi hole size with an increase in UaOg content due to the 

increase in friability, but the instrument error in the caliper and 

perhaps lack of sufficient data obscure the correlation.

COMPARISON OF CORE RECOVERY WITH EQUIVALENT U3O8

CONTENT

Analysis of data on drill-hole diameter and percentage core recovery 

as shown in table 3 indicates a lack of correlation between the core 

recovery and equivalent U3O8 content. Although significant core loss 

in thin, high-grade ore zones is suspected to occur because of occasional discrepancies indicating high activity on the gamma-ray log 

and relatively low equivalent uranium in the recovered ore samples, 

the present data in table 3 do not include any information on thin,
248 EXPERIMENTAL AND THEORETICAL GEOPHYSICS

high-grade ore zones. Thus, no data are available on the possible 

correlation between increasing equivalent uranium content and decreasing core recovery.

CONCLUSIONS

Evaluation of the relationships among data is limited by the accuracy of measurement of the caliper-logging equipment. The use of 

long measuring arms in small-diameter holes causes the angle through 

which the measuring arms move to be small, thus utilizing an undesirable part of the characteristic curve of the tubes in the measuring 

circuit. Use of shorter arms would increase the arc, thereby increasing 

the accuracy of the measurements from the present tolerance of plus 

or minus one-fourth inch.

The following generalized conclusions can be drawn:

1. Variation in drill-hole diameter, particularly through uraniumbearing mineralized zones, is relatively small, in general amounting to 

an increase of less than one-half inch. Such a change in diameter 

would have little effect on the gamma-ray logging measurement, 

probably causing a difference of less than 1 percent in the measurement.

2. The diameter of a drill hole tends to increase with increase in 

particle size.

3. As the diameter of a drill hole increases, the amount of core 

recovered tends to decrease slightly.
TABLE 3. Physical, geologic, and radioactivity data for six drill 

[Analyses of pulverized core by S. P. Furman, Hollis Bivens, James Wahl

Depth 

(ft)

Average 

diameter 

(in.)

Core

Recovered 

(percent)

U3 08 

(percent) 1

Counts per 

minute 2

eU8O8 

(percent) 1

Thickness 

of ore zone 

(ft)

Gamma-ray log

eUaOs 

(percent)

Thickness 

of ore zone 

(ft)

DRILL HOLE JD-327 

[Drill-bit diameter, NX (3.0 in.); total depth, 744

696.0

697.0

RQQ [\

699 0

700.0

701.0

702.0

703.0

704.0

705.0

705.5

706.0

706.5

707.0

707.5

708.0

708.5

709.0

710.0

711.0

712.0

713.0

714.0

715.0

716.0

717.0

71 a n

720.0

721.0

722.0

722.5

723.0

3.75

3.37

3.50

3.12

3.37

3.62

3.37

3.50

3.37

3.25

3.25

3.25

3.25

3.37

3.37

3.50

3.50

3.50

3.50

3.50

3 <?n

3.37

3.50

3.50

3.87

3.37

3.50

3.37

3.50

3.50

3.50

3.12

3.37

100

100

100

100

100

100

100

100

100

100

100

IHfl

100

100

100

100

inn

100

100

100

100

100

100

100

100

100

100

100

100

100

100

0.20

375

Mf\

390

375

<=R(\

1,500

480

410

0.006

.006

.018

.018

.005

.005

nn<?

.007

.007

.007

.007

.007

.007

.003

.012

.15

.018

.005

} "

1 16

J "

\ 1 R

) 1 ' 6

. /

1.7

.6

.6

.6

1.3

<0. 010

.010

.010

.11

0.8

1.7

.8

 

 

 

 

 

 

 

 

 

 

 

 

 

_

 

 

 

 

 

 

 

See footnotes at end of table, p. 255.
TABLE 3. Physical, geologic, and radioactivity data for six drill holes, J

[Analyses of pulverized core by S. P. Furman, Hollis Bivens, James Wabl

Depth 

(ft)

Average 

diameter 

(in.)

Core

Recovered 

(percent)

U3 08 

(percent) 1

Counts per 

minute 2

eU3O 8 

(percent) '

Thickness 

of ore zone 

(ft)

Gamma-ray log

eU308 

(percent)

Thickness 

of ore zone 

(ft)

DRILL HOLE JD-327 Continued

723.5

724.0

79/1 K

726.0

727.0

728.0

729.0

730.0

731.0

7QO fi

733.0

734.0

Q Kf)

3.37

3.37

3.37

3.37

3.37

3.37

3 19

3 

OK

3.25

3.12

3.12

3.00

100

100

100

100

100

100

100

100

100

100

100

100

100

0.034 1.0

_ 

 

. 

_

 

.

 

DRILL HOLE JD-329 

[Drill-bit diameter, BX (2.32 in.); total depth, 550

4(17 n

408 0

409.0

410.0

411.0

412.0

414.0

415.0

416.0

416.5

417.0

417.5

418.0

418.5

419.0

419 a

3

Kn

3 

Eft

3

Q7

3

07

o m

3 

en

3 

OK

0 Kn

3.50

3 

OK

3 

OK

3 

OK

3.37

3.25

3.50

7.5

7.5

7 <?

7.5

7.5

7.5

7 K

7.5

10

10

10

10

10

10

10

10

10

 

.

.

.

 

.

 

 

.

 

. 
420.0

420.5

421.0

421.5

422.0

422.5

At)*> n

424.0

425.0

426.0

427.0

428.0

490 n

/nn n

431.0

432.5

3.37

3.37 3

Q7

3.25

3 

OK

3.25

3.12 3 19

3.00

3.00

3.00

3.00 2

Q7

2.87

2.62

48

48

4Q

48

48

/ta

48

48

79

72

79

72

72

30

30

30

0.011

<-010

<.010

0.6

.8

 

 

 

 

 

 

 

 

DRILL HOLE JD-339 

[Drill-bit diameter, NX (3.0 in.); total depth, 732

650.0

651.0

652.0

653.0

654.0

655.0

656.0

657.0

658.0

659.0

fifin n

661.0

662.0

663.0

663.0

664.0

664 5

665.0

fifi<? <?

666.0

666.5

667.0

667.5

668.0

668.5

669 0

fiftQ 5

670.0

670.5

3

jrn

3 *ft 3

00

3 fi9

3.87

3.62

3.62

O fiO

3.75

3.75

3.62 3 m

3.62

3.62 3

cn

3

07

3.62

3.50

3.50 3

cn

3

m

3.50 3

cn

3.50 3

KA

3.60

3.50

3.50

92

92

Q9

92

92

inn

100

100

100

100

100

100

100

100

100

99

99

99

99

QQ

QQ

99

QQ

99

QQ

QQ

99

99

 

 

 

 

 

 

 

See footnotes at end of table, p. 255.
TABLE 3. Physical, geologic, and radioactivity data for six drill holes, J

[Analyses of pulverized core by S. P. Furman, Hollis Bivens, James Wahlb

Depth 

(ft)

Average 

diameter 

(in.)

Core

Recovered 

(percent)

U3 08 

(percent) 1

Counts per 

minute 2

eUs08 

(percent) 1

Thickness 

of ore zone 

(ft)

Gamma-ray log

eU3 08 

(percent)

Thickness 

of ore zone 

(ft)

DRILL HOLE JD-339 Continued

671.0

671.5

672.0

672.5

673.0

673.5

674.0

674.5

675.0

676.0

677.0

678.0

679.0

680.0

681.0

682.0

683.0

684.0

3.37

3.50

3.37

3.62

3.62

3.50

3.37

3.25

3.50

3.50

3.25

3.00

3.00

3.37

2.75

2.87

2.50

2.50

99

99

99

99

99

99

99

99

100

100

100

100

100

100

100

100

100

100

0.26

.98

2.82

.91

.065

.045

1,229

6,000

6,000

7,000

800

860

630

575

0.21

.73

1.8

.77

.060

.049

0.3

.9

.3

.5

} '

.3

1.30

1.30

1.30 I-----

.012

.012

1.6

1.3

 

 

 

 

 

 

.

 

 

 

 

 

 

 

 

DRILL HOLE JD-341 

[Drill-bit diameter, NX (3.0 in.); total depth, 195

140.0

141.0

142.0

143.0

144.0

145.0

146.0

147.0

148.0

149.0

150.0

3.87

3.87

4.00

3.75

3.75

3.62

3.62

3.75

3.75

3.75

3.75

88

88

88

88

88

51

51

51

51

51

51

.

 

 

 

 

 

 

 

 
151.0

152.0

153.0

153.5

154.0

154.5

155.0

155.5

1P6.0

156.5

157.0

158.0

159.0

160.0

161.0

162.0

163.0

164.0

165.0

166.0

168.0

169.0

170.0

171.0

172.0

173.0

174.0

175.0

3.75

4 19

3.87

4.12

4.25

4.12

3.62

3.75

3.62

3.62

3.37

3.37

3.00

3.12

3.12

3.00

3.12

3.12

3.25

3.37

3.37

3.25

3.25

3.00

2.75

2.87

2.50

51

51

51

51

51

51

51

100

100

100

100

100

100

100

44

44

44

44

44

44

44

44

44

46

46

46

46

46

<0. 010

< .010

1.8

_ 

_

. 

.

.

.

.

.

.

.

 

. 

.

.

 

.

 

 

.

 

 

.

 

.

.

. 

DRILL HOLE A

[Drill-bit diameter, NX (3.0 in.)]

253.0

254.0

255.0

256.0

257.0

258.0

259.0

259.5

260.0

260.5

261.0

262.0

262.5

263.0

263.5

264.0

264.5

4.25

4.12

4.25

4.25

4.12

4.62

9.12

6.62

5.50

4.25

4.12

4.12

4.50

3.87

3.87

3.87

3.75

30

30

30

10

10

10

10

10

10

10

10

10

10

10

10

10

10

<0. 010

<.010

<.010

<.010

<.010

<.010

.03

.03

<.010

<.010

<.010

<.010

1.4

3.0

.8

3.0

.

.

 

 

.

 

. 

.

 

.

.

.

 

.

 

See footnotes at end of table, p. 255.
TABLE 3. Physical, geologic, and radioactivity data for six drill holes, Jo 

[Analyses of pulverized core by S. P. Furman, Hollis Bivens, James Wahlbe

Depth 

(ft)

Average 

diameter 

(in.)

Core

Recovered 

(percent)

U3 08 

(percent) i

Counts per 

minute s

eU3 08 

(percent) l

Thickness 

of ore zone 

(ft)

Gamma-ray log 

eU3 O8 

(percent)

Thickness 

of ore zone 

(ft)

DRILL HOLE A Continued

265.0

266.0

267.0

268.0

269.0

270.0

271.0

272.0

273.0

3.75

3.62

4.00

3.75

3.62

3.62

3.62

3.75

3.50

10

20

20

20

20

20

20

20

20

<0. 010

<0. 010 . 

 

.. 

 

. 

..

.. 

DRILL HOLE B

[Drill-bit diameter, BX (2.32 in.); total depth, 375.0 

260.0

261.0

262.0

263.0

264.0

265.0

266.0

267.0

268.0

269.0

270.0

271.0

272.0

273.0

274.0

275.0

276.0

277.0

278.0

278.5

279.0

4.25

4.12

6.87

7.62

11.00

5.12

4.87

4.87

4.62

4.50

4.50

4.12

4.87

4.62

4.87

5.37

5.25

5.12

4.25

4.25

4.25

50

50

50

50

50

50

20

20

20

20

20

20

20

20

20

20

10

10

10

10

10

<0. 010 1.2

 

 

 

 

 

 

 

_. 

M

 

 

 

..

 

.. 

 

 
CALIPER-LOG, GAMMA-RAY-LOG, OTHER DRILL-HOLE DATA 255

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