GEOLOGICAL SURVEY CIRCULAR 127 0 F 

GEOCHEMICAL AND MINERALOGICAL 

METHODS OF PROSPECTING 

FOR MINERAL DEPOSITS 

Translated from Russian by Lydia Hartsock and A. P. Pierce 
r 

1 
UNITED STATES DEPARTMENT OF THE INTERIOR 

Oscar L. Chapman, Secretary 

GEOLOGICAL SURVEY 

W. E. Wrather, Director 

GEOLOGICAL SURVEY CIRCULAR 127 

Academy ur Science, U. S. S. R. 

GEOCHEMICAL AND MINERALOGICAL METHODS OF PROSPECTING 

FOR MINERAL DEPOSITS 

CHAPTER IV, SPECIAL METHODS OF PROSPECTING 

By A. Ye. Fersman (with articles by S. A. Borovik, G. V. Gorshkov, S. D. Popov, and A. F. Sosedko) 

Published by the Academy of Science Moscow, 1939, Leningrad 

Translated from Russian by Lydia Hartsock and A. P. Pierce, U. S. Geological Survey 

Washington, D. C., 1952 

Free on application to the Geological Survey, Washington 25, D. C. 
FOREWORD 

Fersman's book "Geochemical and mineralogical methods of prospecting 

for mineral deposits" (Geokhimicheskiye i mineralogicheskiye metody poiskov 

poleznykh iskopayemykh) covers all petrographic, mineralogical, and geochemical 

techniques that are used either directly or indirectly in mineral exploration. 

Chapter IV is of particular interest because it describes certain geochemical 

methods and principles that have not been widely applied outside of the Soviet 

Union. 

The original contained a number of photographs that have been omitted; 

the titles of the photographs are given in the body of the text. 

Wherever possible, bibliographic references have been checked, and 

the full titles given. References given in footnotes in the original have been 

collected and added at the end of each section as a bibliography. 

The transliteration of Russian letters follows the form adopted for 

official use by the Board on Geographic Names. This form differs 

from that in common usage for the following Russian letters: 

Russian letter Transliteration 

e e, following a consonant 

ye, at beginning of word and following 

a vowel or soft sign 

r yu 

ya 
CONTENTS 

Page 

Introduction 1 

Methods of geochemical correlation 1 

Methods of studying dispersion 3 

Secondary dispersion halos 3 

Saline dispersion halos 3 

Syngenetic salt halos . 3 

Superimposed salt halos 3 

Mechanical dispersion halos 3 

Syngenetic mechanical 

halos 4 

Buried mechanical halos 4 

Gaseous dispersion halos 4 

General characteristics of 

secondary dispersion • 4 

Examples of studies of 

secondary dispersion halos 5 

Prospecting for salts on the 

lower Volga 5 

Prospecting for primary tin 

deposits 5 

The formation of cassiterite 

dispersion halos 6 

Primary dispersion halos 6 

Example of a mineralogical map 6. 

Kounrad copper deposit 6 

Practical significance of 

Kounrad mineralogic map 7 

The theoretical analysis of 

primary dispersion halos 7 

Combined primary and secondary halos 7 

Appendix: Study of natural emanations 

of dispersed systems of solutions 

and salts 7 

References cited 8 

Heavy-mineral method, by S. D. Popov 8 

Short history and significance of the 

study of heavy concentrates , 8 

Types of placers and the paragenesis 

of minerals in black sands, 10 

Methods of field investigation 11 

The study of heavy minerals in the 

field .. 14 

Page 

Heavy-mineral method, by S. D. Popov--Continued. 

The separation process 14 

Determination of the mineral content 

of heavy concentrates 

Determination of heavy-mineral 

content of the sample 

Bibliography 

The necessary instruments and 

reagents for field work 

Spectroscopic methods, by S. A. Borovik 

Bibliography • • 

Examples 

Fluorescent methods, by A. F. Sosedko, 

with a supplement by A. Ye. Fersman 

Bibliography 

Special methods 

Prospecting based upon the study of 

oxidation processes 

Prospecting by thermal effects 

Prospecting by the chemistry of 

secondary processes 

Prospecting for salt deposits on the 

basis of secondary migration 

The use of redox, or rH (oxidationreduction potential) 

The use of pH determinations 

Botanical methods 

Bibliography 

Visual aerial-survey methods . 

Geophysical methods of prospecting 

Bibliography 

Radioactive methods of prospecting, by 

G. V. Gorshkov 

Introduction 

Emanation method (radon and thoron) 

Gamma method 

Other radioactive methods 

Bibliography 

Appendix 

19 

19 

19 

20 

21 

23 

23 

24 

 26 

 27 

 27 

 27 

 28 

 28 

 28 

28 

29 

 30 

30 

31 

 32 

•.• 

• • 

32 

33 

36 

37 

37 

37 

TABLES 

Page 

Table 9. Gangue and country rock associated with placer deposits 11 

10. Comparison of minerals of the Il'men forest preserve reported in the literature and 

those found in heavy concentrates 13 

11. Electromagnetic data for the separation of minerals 17 

12. Spectral lines used for quantitative analysis of tin 21 

13. Wave lengths of elements detected in the carbon arc 22 

14. Fluorescence of minerals in cathode and ultraviolet rays 27 

15. Concentrations of the radioactive elements 33 

16. Diffusion coefficients for radium and thorium emanations 34 

17. Concentrations of radium emanations as a function of the diffusion coefficient and 

the distance from the source of emanation 34 

111 

GEOCHEMICAL AND MINERALOGICAL METHODS OF 

PROSPECTING FOR MINERAL DEPOSITS 

Translated from the Russian 

Chapter IV 

SPECIAL METHODS OF PROSPECTING 

By A. Ye. Fersman 

INTRODUCTION 

This chapter contains a short discussion of 

the most important special methods of geochemical 

prospecting. These methods are extremely varied. 

Their development and specialization depend upon 

the progress of geochemical and mineralogical 

research. They are based on the laws of distribution of the elements in the earth's crust, in accordance 

with the data of V. M. Goldschmidt. Two groups 

of phenomena determine the paths of migration of 

the chemical elements. One is related to the properties of the earth's materials themselves and leads 

to the establishment of prospecting guides based 

upon the physical, chemical, and mineralogical 

properties of naturally occurring compounds. The 

other is related to environment, and the areal 

distribution of specific conditions which determine 

the accumulation or dispersion of an element. The 

result of the combination cf these two types of 

factors is seen in the establishment of certain 

"physicochemical methods" of prospecting, whose 

principles have been successfully applied to salt 

deposits by V. I. Nikolayev under the partial 

direction of A. P. Vinogradov. V. I. Nikolayev 

in 1937 wrote: 

"Geologic exploration for petroleum and salt 

deposits is usually preceded by physicochemical 

investigations. It should not be forgotten, however, 

that in the time of the celebrated van't Hoff, 

physicochemical studies of salt deposits had achieved 

considerable importance, not only in the solution of 

problems connected with the establishment of the 

character of salt deposits and their origin, but in 

finding means of exploiting them. 

"Physicochemical studies and the application 

of physicochemical analysis to the solution of practical problems permit us to speak of distinct physicochemical (or more accurately, geochemical) methods 

of prospecting for natural resources. 

"In the Kazakhstan session of the Soviet Academy 

of Science it was shown that chemistry, by means of 

its prospecting indicators, is a tool which can and 

does give useful data both for discovering hidden 

deposits and as a guide in other kinds of exploration 

work. 

"For example the ions of potassium, bromine 

and boric acid may be used as indicators in prospecting for potash deposits. " 

V. I. Nikolayev has shown that by means of a 

series of systematic analyses for potassium, bromine, 

and boric acid, areas of greatest concentration may 

be mapped, and with the aid of a diagram showing 

"the movements of the potassium and bromine ions 

with changes of geographic coordinates" one may 

predict the occurrence of potassium and bromine 

salts at depth, such as the residual salt deposits of 

the Permian sea. (Nikolayev, Yanat'yeva, and 

Polyakov, 1937, pp. 857-869; Nikolayev, Yanat'yeva, 

and Frishmut, 1938, pp. 345-348). 

This problem has been expressed even more 

clearly by A. V. Kazakov (1938) in his research upon 

phosphorite facies and the genesis of natural phosphates. 

He has emphasized the importance of using a combination 

of paleogeographic, physicochemical, and geochemical 

investigations. 

METHODS OF GEOCHEMICAL CORRELATION 

The problems of geochemical correlation of 

elements and minerals are very complex as they lie 

at the foundation of the mineralogy and geochemistry 

of natural associations and paragenesis. 

Every paragenesis is a definite, regular 

association of elements and minerals which are 

related by specific chemical processes. In this 

sense every natural association of minerals gives 

us a clue to the elements or minerals that can occur 

in the given paragenesis. Also, these associations 

may show the improbability of some substance being 

present in a particular area. 

For example, it is necessary to restrict the 

search for lithium to associations of albite, quartz, 

clear beryl, and microcline, which are the paragenetic 

1 
List of paragenetic associations 

Li - Be - B 

Fe - Ba - Pb 

F - Al - (P) 1/ 

Mg- Fe - Cr 7 (Ni) 

P - Ca - (rare earths) 

S - Heavy metals 

S - Sr - bitumen 

Cl - Na - (K, Rb, Cs, Ca, Mg) 

• - Rb - Cs - (Li) 

Ca - Na 

Sc - Mg 

Ti - Fe - (Ca) 

✓ - U - Ra - (bitumen) 

Cr - Ni - Mg - Fe 

Fe - Co - Ni - Cr 

Co-Ni - Fe - Mn 

Ni - Co - Fe 

Zn - Cd - Ga - Ge - In 

Zn - Pb - Ag 

As-Au 

Br-Cl - I - (Cs, Rb) 

Rb-Cs 

Sr - (SO4)- S - dolomite 

Zr - Ti - (Nb, Ta) 

Nb - Ta - Ti - Zr 

Mo - W - (Sn) 

Ag - Pb - Co 

Cd - Zn 

Sn - W - Li 

Sb - As - S 

Te - Au - Ag - Hg 

I — Br - Cl 

Cs - Rb - (Li) 

Ba - (SO4)- (Pb) 

W - Sn - (Au) 

Au - Ag - As -•(Te) 

Hg - As - Sb 

Pb - (Zn) 

Th - rare earths 

U - Ra - (V, As, P) 

1/ The parenthesis are reproduced as given in the 

original; no explanation was given as to their 

significance. 

In addition to the correlations of elements 

resulting from the general laws of geochemical 

association, we have a. number of special rules, 

which may be applied under certain circumstances. 

For example a number of authors have noted 

interesting correlations with the different degrees 

of oxidation of vanadium: V+5is associated with 

bitumen, and V+3with the primary silicates. Thus 

in prospecting for petroleum an increased V+5: 

V-1-3ratio indicates an increased concentration of 

bitumen in the rock. (Baturin, 1938) 

'Translators' note: geophase F-G represents the temperature range 

between 400° and 500° C. See Fersman, A. Ye., Pegmatity, vol. 1, Chap. 4, 

pp. 37-39, 1940. 

2 

A particularly interesting example is the use 

of strontium correlations as a prospecting indicator 

in the European part of the U. S. S. R. and in the 

Ural Mountains. Celestite, gypsum, rock salt, 

anhydrite, and copper compounds are the most 

characteristic minerals of the marine Permian beds. 

V. I. Nickolayev has drawn attention to the fact that 

there is a marked difference between the composition 

of the Caspian Sea and its deposits, and the probable 

composition of the Permian sea and its deposits 

(Nikolayev and Kalinin, 1938). This can be seen.from 

the large concentrations of sodium chloride in the 

Permian sediments as compared to the accumulation 

of magnesium and calcium sulphates in Caspian 

sediments. The hypothesis that some orderly process 

led to a greater concentration of strontium sulphate. 

in the Permian sediments as compared to the Caspian 

sediments is confirmed by a number of analyses. 

In view of this the following conclusion by Nikoloyev 

appears to be entirely logical: 

"We can now regard the strontium ion as a new 

prospecting indicator, which like K or Br may be 

used to establish the genesis of salt deposits and 

natural waters, and to differentiate between Caspian 

and Permian salt deposits. Concentrations greater 

than 0.02 percent Sr are characteristic of Permian 

salt deposits, while concentrations that do not exceed 

0.01-0.02 percent may be regarded as typical of 

Caspian deposits. 

"Basins of purely Caspian origin, such as Ozero 

Balkhash, are characterized by Sr concentrations in 

the order of thousandths of a percent, while the Sr 

concentrations of the brines and springs of Ozero 

Inder range from 0.02 to 0.08 percent Sr, which 

immediately shows a connection with Permian salt 

deposits. " 

There is little doubt that as the result of 

further investigations in different regions, other 

elements may become important as prospecting 

indicators. 

On the basis of the examples given above we may 

define the idea of geochemical correlation as follows: 

We generally understand correlation to be the 

method of comparing sedimentary rocks according 

to their preferential associations (this would also 

apply to magmatic and metamorphic rocks). In 

particular, however, we will define a geochemical 

correlation to be one which is ,based upon the methods 

of comparing the concentrations of different chemical 

elements. 

The use of specific chemical features for tracing 

the continuity of sedimentary layers in complex 

formations is of great interest and is being constantly 

applied by various scientists, especially in the Soviet 

Union (Ya. V. Samoylov: "On the principle chemical 

elements analogous to the principle minerals", 1913; 

A. F. Fioletova: in a number of interesting articles 

on clays, 1925-1929; A. Vezir-Zade and M. Mirchink: 

"The experimental correlation of petroleum-bearing 

beds according to the carbon coefficient. "; and so on). 

2/ The large volume of accumulated information does 

not allow us to generalize as yet with regard to this 

very complex question, as we do not possess enough 

21n the foreign literature upon geochemical correlation may be noted, 

for example, the work of Leith and Meade, and others. 

constituents of the geophase "F-G" 1/ in granitic 

pegmatites. It would be illogical and incorrect 

to prospect for ores of nickel and chromium in 

such an environment. 

We will limit ourselves only to listing some 

typical, regular associations: 
Country rock + 

weathering agents. 

Primary sulfides + 

weathering agents. 

Mineral 

absorbing 

complex. 

Electrolytic 

solutions 

(chiefly sulfates). 

systematic analyses of complete sedimentary suites, 

either in vertical or horizontal cross section. 

Nevertheless this method deserves the attention of 

stratigraphers, especially in the study of coal and 

petroleum deposits. We hope that there will be 

additional excellent research such as the correlation 

of petroliferous rocks of the Apsheronskiy Poluostrov 

[Apersheron Peninsulal by means of petrographic and 

mineralogical indicators (Baturin and Gubkov, 1929). 

As an example here, I wish to cite the very 

interesting research of V. Levinson and A. Kocharev 

(1930) who developed the idea of stratigraphic correlation by means of the concentration and degree of 

oxidation of vanadium. The authors proceeded from 

the laws of the geochemical distribution of V203 and 

V205 in rocks, by which the former is related to 

silicate systems of primary origin, whereas the 

second is related to organic matter. Thus, V203, 

which is highly dispersed, may be used for correlations, which V205 indicates the bitumen content of 

rocks. 

METHODS OF STUDYING DISPERSION 

The above example of the roles that strontium, 

boron, and bromine play as prospecting indicators 

shows us that the types of distribution and dispersion 

of some elements are of interest to the prospettor. 

Dispersion can be divided genetically into two 

types. One type is of a secondary character and 

is the result of the mechanical and chemical dispersion 

of previously formed deposits. The other type is a 

primary dispersion pattern of the given element or 

substance. The problem is to find a method for 

locating places of concentration within the primary 

phases on the basis of the fundamental laws of 

geochemical distribution. 

Secondary Dispersion Halos 

The dispersion of elements and minerals in 

sands and placer deposits is confined to definite areas 

determined by the geochemical and geoenergetic sic 

properties of the given compounds. 

'On the basic of a number of experiments N. I. 

Sofronov (1936) has come to the following conclusions: 

The term "dispersion halo" of a mineral deposit 

may be defined as that zone of "eluvium-deluvium" 

[ see "deluvial placers" p. 101 (in some cases alluvium) 

which has been enriched by a characteristic element 

derived from a primary deposit without regard for 

the state of aggregation of the element. The term 

embraces the areal aspects of the pattern, and the 

processes by which the mineral deposit passes from 

a state of concentration to a state of secondary 

dispersion. 

The principal agents causing the formation of 

dispersion halos are those of supergene surface 

weathering. 

Halos may be classified first according to the 

dispersed element under consideration, and also 

according to the origin of the halo with due regard for 

the transient state of the eluvium-deluvium and of the 

dispersed phase. 

Saline Dispersion Halos 

In saline halos the indicator element occurs as 

recently deposited material, usually as a soluble salt 

in the weathering zone, such as a sulfate. 

The laws for the formation of these halos involve 

both chemical and physical principles. 

Saline halos characteristically form in the 

weathering zone of deposits, such as polymetallic 

sulfide deposits. A schematic diagram showing the 

typical evolution of the halo of a sulfide deposit 

follows: 

Saline dispersion halos 

Phenomena causing the evolution 

and fixation: 

1. Coagulation of the colloids 

of the absorbing complex by 

electrolytes. 

2. Diffusion and capillary 

ascent. 

3. Adsorption of the electrolytes 

by absorbing complexes through 

diffusion and capillary ascent. 

From the viewpoint of genesis we may differentiate 

between the follo-wing: 

Syngenetic salt halos. --The absorbing complex 

is represented by eluvium-deluvium which has been 

formed simultaneously with the electrolytes. Coagulation of the colloids of the absorbing complex by the 

cations of the electrolytes is most important during 

the evolution and fixation of the halo. Later, the 

principal role is played by diffusion and capillary 

action accompanied by adsorption of the cations. 

Superimposed salt halos. --The absorbing 

complex is represented by alluvium; solutions more 

3 

recent than the mantle are formed. Capillary action 

and diffusion accompanied by adsorption of the cations 

are most important in the evolution and fixation of the 

halo. These halos are less easily reached in surface 

prospecting. 

Mechanical Dispersion Halos 

The indicator elements of mechanical dispersion halos 

will be found in the form of primary minerals which 

are stable in the weathering zone. 

The laws for the formation of the halos are both 

physical and physiochemical. 
Country rock + 

weathering agents. 

Quartz-cassiterite 

vein. 

Reduction in volume 

of eluvium-deluvium 

layers. 

Friable vein material 

without loss, 

Mechanical halos are characteristic of those 

deposits which are composed of stable minerals 

occurring within the weathering zone, such as deposits 

containing cassiterite, wolframite, chromite, native 

gold, molybdenite, and others (Andreyev, 1931). 

A schematic diagram of the evolution of a 

typical mechanical halo from a quartz-cassiterite 

deposit may be presented as follows: 

Mechanical dispersion halo 

Factors resulting in the evolution and fixation of a mechanical 

dispersion halo: 

1. Accommodation of the ore 

sands to the natural angle of repose of a stream profile. 

2. Mixing of the ore materials 

with eluvium-deluvium. 

3. Gravitational differentiation. 

Besides the conditions necessary for the formation of mechanical halos we wish to add the following: 

Ore minerals may be released during weathering from the wall rocks of the vein where the minerals 

usually occur either as disseminated crystals or in 

small stringers which are associated with the principal 

vein. The release of these materials tends to intensify 

the halo. 

A marginal drift or general creep of the eluviumdiluvium may result in deformation of the halo. 

From the viewpoint of genesis the following 

classifications can be made: 

Syngenetic mechanical halos. --The weathering 

of the country rock produces eluvium-diluvium with 

the vein simultaneously contributing particles of ore 

materials. This type of halo is the most important 

in prospecting. 

Buried mechanical halos. --The overlying rocks 

are alluvial and have been transported from a distance. 

The halo was formed earlier or is formed under the 

alluvium. From the standpoint of prospecting, these 

halos present a more difficult problem. 

Gaseous Dispersion Halos 

In this type of halo (Chikrysov, 1938, pp. 62-64) 

the indicator element occurs in the gaseous phase. 

The laws of the formation of these halos are chemical, 

physicochemical, and physical. Gaseous halos are 

especially characteristic of deposits containing gas 

either as the economic product (as in a helium deposit), 

as a natural by-product (as in a petroleum deposit), 

or as the product of the radioactive decay of primary 

material (radium-uranium and thorium deposits). 

A schematic diagram of the formation of a 

gaseous halo would show how gaseous products are 

distributed by diffusion within primary rocks from 

which they enter the eluvium, or are taken up by 

water in the form of characteristic solutions. 

From the genetic viewpoint the gaseous halos 

associated with oil pools are obviously of the superimposed type, whereas the halos associated with 

radioactive deposits are syngenetic. 

General Characteristics of Secondary Dispersion 

The interesting ideas of N. I. Sofronov presented 

above undoubtedly deserve attention, but need a more 

detailed development with regard to the particular 

geochemical processes. 

We may assume that mechanical dispersion 

halos depend upon the value of the "ek" 3/ and the 

combining energy of the lattice since the higher the 

combining energy of the lattice, the greater the 

stability and•the larger the radius of dispersion of 

the primary mineral. 

A deviation from this rule results from the 

mechanical properties of minerals, such as where the 

friability of a mineral causes it to be readily pulverized. 

It is interesting to note that the size of a saline 

halo is related to the type of absorption and the degree 

of polarization of the ions. The latter is especially 

critical and undoubtedly determines the extent of 

absorption and type of coagulation (according to W. 

Noll). 

Naturally, the practical application of the theory 

of halos must be studied and proved in detail. In 

saline halos associated with sulfide deposits the 

concentration of sulfate ion may be traced within areas 

of contrasting supergene processes. For mechanical 

halos the minerals can be arranged in the order of 

diminishing size of halo. The figures after the 

minerals in the following list give the mean "paragens." 

by my computations. 

Diamond 12 Magnetite 3. 3 

Zircon 4 Scheelite .. 2 5 

Quartz 4 Hematite 3. 0 

R utile 4 Woiframite 2 

Cassiterite 4 

3Translators' note: In Fersman, A. E., The periodic system of energy 

coefficients (in English): Acad. Sci. U. R. S. S., Comptes rendus, v. 3, 

pp. 173-176, 1935, the "ek' is defined 'as the amount of energy which an 

ion of definite valency existing in infinity contributes on passing into a2 

system of a heterpolar crystal lattice." It is numerically equal to K 

where K = constant, w = valence, R = ionic radius. 

4 
Note that this series decreases from left to 

right in the same order as the mean "eks" and "veks" 

of the cations. Further research into this problem 

will, undoubtedly, clarify the situation and yield more 

accurate methods of locating halos on the basis of the 

concept of paragens, and confirm the figures for distance of migration for different minerals. 

Examples of Studies of Secondary 

Dispersion Halos 

Prospecting for. salts on the lower Volga. --An 

excellent example of the methods of geochemical 

prospecting is furnished by the work of a salt-prospecting expedition in the Primorsk district, Kalmyk A. S. S. R. , 

1937 (Nikolayev, Yanat'yeva, and Polyakov, 1937, pp. 

857-869; Nikolayev, Yanat'yeva, and Frishmut, 1938, 

pp. 345-348). Samples were collected and quantitatively 

analyzed from twenty drill holes and shallow pits. The 

results show not only a variable concentration of bromine 

and particularly boron, but higher concentrations as compared with the waters of the Caspian Sea. A high concentration of boric acid (0.9 percent) was found in deep drill 

holes (as much as 200 m), and also in shallow pits. 

"By plotting on a map points, which clearly showed 

an increased concentration of potassium, bromine, and 

boric acid in the waters, two areas in the Primorsk 

district were indicated where the presence of both 

potash and borate deposits may be expected at depth. 

Specifically, the data of this physicochemical survey 

indicate that the area around and to the northwest 

of the Ulan-Tug state farm, and also the area between 

Olenichev and the river Ulan-Khol are most favorable 

for the discovery of potash and borate deposits. 

"With regard to the question of why the waters 

of springs and artesian wells accumulate such large 

quantities of boric acid we may tentatively assume that 

there is a washing out of the borate deposits at depth 

by waters that are rich in magnesium sulfate. All the 

lakes in the Primorsk region have high concentrations 

of magnesium sulfate in their brines. " Thus, by the 

application of geochemical• methods, maps were made 

of the areas containing the highest concentrations of 

bromine, boron and potassium salts at depth. 

Prospecting for primary tin deposits. --Soviet 

scientists have worked out excel-Fent methods for 

prospecting for primary tin•deposits by means of 

dispersed deposits (Ozerov, 1937; Flerov, 1935; and 

1938; Sarkisyan, 1939). The following is an excerpt 

from the interesting work of B. L. Flerov: 

"The distance of transport •of cassiterite from 

the primary deposit depends chiefly upon the longitudinal 

profile of the valley. The greater the grade of the river 

bed, the greater will be the strength of the current, 

which determines the size and weight of the transported 

particles. In regions of active vertical erosion, for 

example, Verkhoyansk and Kolyma districts, the steep 

grade of the valley prevents the friable cassiterite, 

which has a lower specific gravity than gold, from 

accumulating in large placer deposits. The larger 

part of it is transported to considerable distances 

and is dispersed. Deposits formed in areas of more 

gentle relief, like Transbaikal, undoubtedly would 

contain sands of economic value. Naturally, favorable 

conditions for deposition are locally possible in 

mining districts, and consequently cassiterite placers 

may occur in these regions, especially in the vicinity 

of coarse fragments of cassiterite. 

"The formation of placer deposits depends upon 

the manner in which the cassiterite is distributed in 

the ore-bearing rock and the composition of the rock. 

The more coarse the segregations of cassiterite or its 

individual particles, the more concentrated and closer 

to the original deposit will be the placer deposit. The 

formation of a placer deposit is favored by an erratic 

distribution of cassiterite in the vein, whereby coarse 

fragments of high specific gravity are found. On the 

other hand finely disseminated cassiterite will be 

transported further both because of its small size and 

because its separation from the gangue occurs during 

transport over a greater distance. Sulfide veins with 

microdisseminated cassiterite as a rule do not yield 

productive deposits. 

"The vein minerals must be resistant to produce 

the large segregations that result in concentrated 

deposits. If the vein material is easily weathered 

there will be no cohesion in the cassiterite segregations and they will break up into small particles. 

Cassiterite disseminations associated with resistant 

minerals will break up during long term transportation and result in scattered deposits. In this case 

it is better if the cassiterite is disseminated within 

softer minerals from which it will separate more 

quickly. However, if the vein minerals are too soft 

this will lead to a grinding up of the cassiterite 

already in the deluvium. 

"Minerals associated with cassiterite will not 

serve as independent prospecting indicators. In 

most deposits cassiterite occurs in sufficient quantities so that if it occurs in the primary deposit it 

will be found in the sediments. Sulfide veins with 

microdisseminations of cassiterite are the only 

exceptions to this rule. In this case the sulfides or 

their alteration products are prospecting indicators, 

even though the tin is high grade. 

"The heavy mineral associations in alluvium 

may give indications as to the type of deposit. The 

association of cassiterite with sulfides indicates 

hydrothermal deposits. An association with topaz 

indicates pneumatolytic deposits. An association 

with the tantalo-niobates indicates a pegmatite deposit. 

Clear, needle-like tourmaline is very characteristic 

of deposits that are transitional from hydrothermal to 

pneumatolytic. Dark tourmaline is usually a negative 

indicator because it is formed at an earlier stage 

than cassiterite. Green chlorite is often associated 

with cassiterite in the northeast part of the U. S. S. R., 

and seems to take the place of tourmaline in deposits 

free of boron emanations. The association of cassiterite with albite, orthoclase and muscovite may point 

to pegmatitic as well as pneumatolytic types of deposits. 

If the cassiterite is associated with adularia it indicates 

a hydrothermal deposit. Wolframite and scheelite are 

frequently associated with cassiterite in deposits of the 

transitional type, but most often these minerals occur 

separately and are not characteristic. 

"Gold is frequently associated with cassiterite 

in the sediments of some regions, but it is usually 

not derived from the vicinity of the primary 'cassiterite 

5 
deposit. However, these minerals may occur together 

in sulfide deposits and under some hypabyssal conditions. 

"The crystal form of cassiterite may also be an 

indication of the type of primary deposit. (See page 

382) [not translated' 

"The formation of cassiterite dispersion halos. --

DuringThe weathering of the primary ore body, part 

of the cassiterite breaks loose directly from the outcrop 

of the vein, another part is separated from blocks as 

they move down the slope, and a third part reaches the 

bottom of the slope in the form of aggregates of cassiterite and gangue. The cassiterite freed from other 

vein material moves down the slope with the deluvium, 

and under the influence of gravitational differentiation 

is concentrated in its lower layers. 

"The more gentle the slope and the greater the 

amount of deluvium, the deeper is the enriched layer. 

The depth to which it settles also depends upon the 

type of deluvium. One often sees slopes covered with 

fragmental material or granitic gravels. Cassiterite 

can easily settle through these loose layers and re....ch 

the more compact layers of deluvium, or even bedrock. 

The most favorable materials for the concentration of 

cassiterite appear to be dense clayey sands or clayey 

detrital material. We have noticed that cassiterite 

is found near the top of such materials. Cassiterite 

may also be found in small fragments which have low 

specific gravity and occur higher in the deluvium than 

the grins of cassiterite. Pulverized cassiterite will 

rise into the upper layers of the deluvium, except, of 

course, the humus. By the author's observations the 

thickness of such enriched layers reaches several 

tens of centimeters. 

"The schematic diagram of the dispersion halo 

takes the shape of a fan, widening slightly toward the 

bottom. Owing to the dispersion of the cassiterite within 

the mass of the diluvium,its concentration in the halo 

is of course smaller than in the source rocks and 

diminishes towards the edges of the halo. The greater 

concentration of cassiterite will be found next to the 

vein where the amount of dilution of the vein material 

has been insignificant. At this place the enriched layer 

of the deluvium merges into the primary rock. 

"A 0.01 percent concentration of tin in the halo 

is a good indication for prospecting. According to the 

data of the Geophysics Branch of Central _ScientificResearch Geological-Prospecting Institute, the width 

of a typical enriched halo is from 25 to 30 meters 

measured perpendicular to the vein. " 

On the basis of his work in Transbaikal, S. G. 

Sarkisyan states that cassiterite disintegrates quickly, 

and does not resist transportation for distances greater 

than from 0.5 to 2 kilometers from the primary deposit. 

Primary Dispersion Halos 

The' establishment of favorable loci for the 

concentration of any mineral or chemical element is 

related to processes of precipitation of solid matter 

from more dispersed fluid or gaseous systems. 

Certain definite conditions of temperature, pressure, 

and wall-rock composition must prevail before crystallization can begin. Furthermore, such precipitation occurs 

6 

over a definite time and area (the halo, or more 

accurately the areal dispersion pattern of a given 

compound). High concentrations of material occur 

only locally, and are surrounded by primary dispersion halos. It is interesting that Elie de Beaumont 

in 1847 spoke of primary halos of elements distributed 

about granite masses, calling them "aura granitica". 

This is true of chromite, magnetite, and titanomagnetite 

ores deposited at lower temperatures. Because the 

sites of highest concentration are surrounded by 

zones of progressively dispersed ore material, the 

making of an accurate survey of the dispersion halo 

may lead to the location of the center of mineralization. This is done by plotting isograds (lines of 

equal concentration) of the given substance or elemeht 

to discover the direction of increasing concentration 

and the areas of greatest enrichment. The Americans 

in particular have used this method to a large extent, 

naming it according to the nature of the metal, as: 

cuprometric or stannometric. It is based upon 

systematic analyses for the given element in samples 

collected on both horizontal and vertical grids. The 

areas of highest concentration can then be plotted in 

three dimensions. Frequently this method is called 

"geometrical. " See chaptr on mapping page 144 

[not translated]. 

Such methods of geochemical mapping are of 

great importance in prospecting and in the solution of 

theoretical problems (methods of the Chinese scientists, 

Shu and Li). However, results of systematic sampling 

and the compilation of geochemical maps may be further 

enhanced by compiling "mineralogical maps". These 

are diagrams of the distribution of minerals rather 

than chemical elements on a three dimensional grid. 

Ya. D. Gotman (1936, pp. 1-64) has given us an 

excellent example of such maps in his mineralogical 

analysis of the Kounrad deposits. 

Example of a Mineralogical Map 

Kounrad copper deposit. --The mineralogical 

map of the Kounrad porphyritic copper deposits is 

the first attempt at compiling a map of this type. 

Such a map is the result of systematic mineralogical sampling and should form the basis for orerecovery studies. Therefore such maps should be 

part of the survey of every mineral deposit. 

In Kounrad where the ore mineral is distributed 

throughout the rock quite uniformly as compared with 

other types of deposits,' random-sampling methods 

are justified. 

In other types of mineral deposits, such 

as veins and mantas where the distribution of 

the ore minerals in the rock is extremely" 

variable and the thickness of the ore bodies is 

small, the method of random sampling must 

be replaced by a method of systematic sampling. Samples are collected a- meter apart and 

broken up. (Core samples or bores from prospecting pits or shafts may be collected.) A 

typical sample is polished and a thin-section is 

prepared for analysis. Mineralogical analysis 

of crushed ores is described in detail in an 

article by A. A. Glagolev and Ya. D. Gotman, 

(1934). 
The bulk-sampling method may be applied to 

porphyritic and stockwork types of ore deposits when 

it is desirable to obtain the exact content of a metal or 

mineral within a particular zone or horizon, or in a 

deposit of small areal extent. 

Therefore, the use of the mineralogic method of 

sampling depends on the structure of the mineral 

deposit, its thickness and the distribution of ore minerals. 

The mineralogical map is not only of practical 

importance but also has considerable theoretical 

importance in solving questions of the origin of mineral 

deposits. Although such a map does not supply complete 

information regarding the genesis of mineral deposits, 

it does provide good supplementary information on the 

history of the formation of a mineral deposit. 

Practical significance of Kounrad mineralogic 

map. --Mineral distribution charts plotted on horizontal 

arWvertical sections of the ore deposits show the distribution of the ore and the principal non-ore minerals 

in the central Kounrad area. (Malachite, azurite, 

covellite, chalcopyrite, chalcocite, andalusite, quartz .

and others have been plotted). 

The outstanding parts of the mineral deposit, in 

which there has been great industrial development, has 

a zone of oxidation in contrast with other areas where 

this zone is absent. 

Within the boundaries of sulfide zone, the enriched 

and the impoverished areas may be distinguished. 

In compiling the map, examinations were made 

of 4000 polished sections and of 100 thin sections, 

representing samples from 25 drill holes. 

The author reaches the following completely 

accurate conclusion: In mining ores with a low metal 

content, such as porphyritic ores, special methods of 

treatment are used. The smelting process which is 

profitable for high-grade ores gives way to a combination of smelting preceded by concentration, which is in 

most cases a physical or physicochemical process, 

depending on the properties of the ore minerals. 

Therefore, in concentrating ores one should be 

'familiar with the quantitative mineral composition of 

the ore, as well as the properties of these minerals, 

inasmuch as differing properties of the minerals make 

it necessary to use different methods of concentration 

on ores from different deposits. 

The Theoretical Analysis of 

Primary Dispersion Halos 

Geochemical analysis (Fersman, 1937, p. 451) 

helps to make clear the processes of dispersion and 

indicates those types of atoms and compounds which 

possess the highest mobilities and which occur most 

frequently in large halos. A detailed discussion of this 

subject may be found on page 40 (Chapter I) [not 

translated'. Compounds with ions of large radii and 

small energetic coefficients (eks and veks) should 

have the highest mobilities; that is, ions of low valence, 

and complex molecular ions with large radii. Examples 

are: Cs - a univalent cation, with the lowest ek and 

vek for cations (0. 30), and with a very large radius 

7 

(1. 65X ); and (NO3) - a univalent anion, with a 

very 

A. 

ek and vek (0. 19), and a radius of 

2.57 

As a result of these relationships, I have set 

up the equation D .4-; which gives the relative 

mobility of the ion, and its maximum dispersion away 

from the primary magmatic nuclei. As an example, 

D for Na = 0.98 and D for Cs = 1.65; in the metallic 

group: D for zinc = 0.21 and D for cadmium = 0.26. 

A more detailed and exhaustive study of this constant 

is necessary. 

Combined Primary and Secondary Halos 

Guided by the principles of primary and secondary 

dispersion of elements, we can better study regions 

where a general deficiency or abundance of a particular 

element exists. Regions that are deficient or rich in 

certain elements have been studied in detail from the 

economic, medical and geochemical point of view by 

A. P. Vinogradov. For our purposes, we are chiefly 

interested in high clarke values 4/ in a give* area. 

For example, a positive clarke value for mercury, 

iron or lithium will reveal an area of enrichment as a 

guide to exploration. By a positive clarke we mean 

concentrations which are greater than the average 

clarke of the earth's crust; negative ones are those 

that are below the average clarke value, On the other 

hand, negative values should be taken into consideration 

in making a thorough geochemical survey; for instance, 

a deficiency of sulfate ions in water may indicate the 

presence of petroleum or coal, or may reveal concentrations of radium and mesothorium in the water. 

A low concentration of calcium and magnesium Li 

water, especially in petroleum districts, may point 

toward increased concentrations of boron salts, or 

other salts. 

Appendix 

Study of Natural Emanations of Dispersed 

Systems of Solutions and Salts. 

Minerals are defined as those compounds which 

are relatively stable and are fixed in stable crystalline 

systems with the largest entropy and the highest 

symmetry. However, geochemical processes are not 

limited to these ultimate products of chemical processes; 

in intermediate circumstances, we may expect a more 

complex picture of solutions and gases than is seen in 

solid materials. With regard to titanium account must 

be taken of the transient compounds, TiF4 and TiC14, 

which are very important in the migration of titanium. 

Therefore, the study of transient minerals of the 

geochemistry and mineralogy of temporary gaseous or 

liquid systems, may be of great value in prospecting. 

This idea brings to mind the early studies of 

gaseous emanations, begun so brilliantly by Elie de 

Beaumont, and continued by LaCroix, Zambonini, 

Karobbi, and Vernadskiy and which achieved remarkable 

results in the work of the Carnegie Geophysics Laboratory in Alaska (Katmai). It is important that similar 

investigations be made in Kamchatka and in the Caucasus. 

4Translators' note: The word "clarke", introduced by the Russians 

in honor of F. W. Clarke, author of the Data of Geochemistry, means the 

average content ,of a given element in naturally occurring material. When 

unqualified, it usually refers to the earth's crust. 
In the same manner we have a problem in the 

study of mineral waters, juvenile as well as vadose, 

which are interesting not only for their chemical properties but also for their characteristic associations. 

Following this lead (V. Vernadskiy),we may obtain 

a completely new concept of the course of geochemical 

processes. The study of the composition of solutions and 

gaseous emanations may reveal guides in prospecting 

for valuable minerals, especially rare metals. 

References Cited 

Andreyev, B. A., 1931, Tsentral'. nauchno-issledov. 

geol. -razved. inst., no. 10, p. 34. 

Baturin, V. P., 1938, Fluorite in the Kurgurian 

limestones and dolomites of the Ural-Emba region: 

Acad. Sci. URSS. Comptes rendus, no. 6-7, pp. 

503-506. 

Baturin, V. P., and Gubkov, P., 1929, Mikropetrograficheskiy metody parallelizatsii neftyanykh 

otlezheniy [Micropetrographic method of correlating 

petroleum deposits]: Azerbaydzh. neft. khoz., 

no. 6-7, p. 10. 

Chikryzov, G. S., 1938, Gazovaya s"yemka [Gas 

survey': Razvedka nedr, no. 7, pp. 62-64. 

Fersman, A. Ye., 1937, Geokhimiya, vol. 3, pp. 

321-350. 

Flerov, B. L., 1935, Primeneniye olovometricheskoy 

s"yemki pri poiskakh korennykh mestorozhdeniy 

olova [Application of the stannometric survey to 

the exploration of primary tin deposits1: Redkiye 

metally, no. 1. 

1938, K metodike poiskov korennykh olova [On 

methods of prospecting for primary tin deposits I: 

Sov. geologiya, v. 8, no. 10, pp. 63-81. 

Gagolev, A. A., and Gotman, Ya. D., 1934, 

Kolichestvennyy mineral-ogicheskiy analiz droblenykh 

rud r Quantitative mineralogical analysis of crushed 

ores]: Min. Syr'ye, no. 3. 

Gotman, Ya. D., 1936, Mineralogicheskaya karta 

Kounrada i metodika yeye sostavleniya [The Kounrad 

mineralogical map and the methods of its compilation]: 

Vses. inst. min. syr'ya, no. 97, pp. 1-64. 

Kazakov, A. V., 1938, Fosforitnye fatsii i genesis 

prirodnykh fosfatov [Phosphorite facies and the 

genesis of natural phosphates]: Sov. geologiya, vol. 

8, no. 6, pp. 34-47. 

Levinson, V., and Kochkarev, A., 1930, Nekotorye 

voprosy neftyanoy geologii i redkiye elementy 

[ Some problems of petroleum geology and rare 

elements': Azerbaydzhan. neft. khoz., no. 7-8. 

pp. 74-89. 

Nikolayev, V. I., and Kalinin, S. K. , 1938, Strontsiy 

kak odin iz khimicheskikh poiskovykh priznakov 

[ Strontium as a geochemical prospecting indicator1: 

Akad. Nauk SSSR Doklady, new ser., tom 20, no. 6, 

pp. 465-466. 

Nikolayev, V. I., Yanat'yeva, 0. K., and Frishmut, 

M. A., 1938, Fiziko-khimicheskaya razvedka 

1937g. v Primorskom rayone Kalmytskoy ASSR 

[Physicochemical survey of 1937 in the Primorsk 

region of the Kalymyk A. S. S. R.1: Akad, Nauk 

SSSR Doklady, tom 18, no 6, pp. 345-348. 

Nikolayev, V. I., Yanat'yeva, 0. K., and Polyakov, 

V. D., 1937, Fiziko-khimicheskaya kharakteristika 

rayonov solyanykh kupolov Stalingradskogo kraya i 

Kalmykii [Physicochemical characteristics of the 

salt dome districts of the Stalingrad region and 

8 

Kalmyk]: Akad. Nauk SSSR Izv. , ser. khim. ; no. 4, 

pp. 857-869. 

Ozerov, P. M., 1937, Stannometricheskaya s"yemka 

kak poiskovyy metod [ Stannometric method as a 

prospecting method]: Razvedka nedr, no. 24, pp. 

52-56. 

Sarkisyan, S. G., 1939, Petrografiya rykhlykh 

kassiteritsoderzhashchikh otlozheniy Zabaykal'ya 

[The petrography of the cassiterite-bearing deposits 

of Transbaikal], thesis and dissertation, Moscow. 

Sofronov, N. I., 1936, K voprosy ob oreolakh 

rasseyaniya [On the problem of dispersion halos]: 

Probl. sov. geologi.ya, no. 4, pp. 302-323. 

HEAVY MINERAL 5/ METHOD 

By S. D. Popov 

Short History and Significance of the Study of 

Heavy Concentrates 

The Americans were pioneers in the study of 

mineral products found in alluvial deposits, especially 

in the heavy residues separated by washing--the socalled heavy concentrates.- In 1853, Blake studied 

heavy minerals from sedimentary sands on the shores 

of the Pacific Ocean, where he found that the black 

sand contained from one to three tenths as much 

platinum as gold. In 1873, Silliman studied not only 

gold and platinum in heavy concentrates, but also other 

minerals, such as chromite, magnetite, zircon, rutile, 

garnet, diamonds, topaz, pyrite, and others. A 

systematic study of black sands in the United States 

was begun in 1905, when Congress authorized the 

Geological Survey to investigate thoroughly the sands 

on the shores of the Pacific Ocean and in other parts 

of the United States. The principal object of this 

investigation was to examine the mineralogical content 

of deposits of grey and black sands, as well as the 

possibility of their commercial utilization. This study 

of black sands in the United States has permitted the 

American scientists Robert Richards, David Day, 

H. Milner, C. Raeburn and others to work out detailed 

techniques for investigating heavy-mineral concentrates, 

such as methods of identifying the rare earth minerals, 

heavy minerals, field procedures, and sampling 

techniques. For the separation of black sands into their 

constituent minerals, special concentration plants 

equipped with the latest technical devices were developed, 

which enabled American commercial organizations to 

obtain nearly pure concentrates of wolframite, scheelite, 

cassiterite, zircon, and others. The Americans were • 

thus in a position to develop practical uses for the 

products from black sands. 

Other countries were also recovering minerals 

from black and grey sands. For instance, English 

companies obtained diamonds from the alluvial deposits 

of Brazil; Japan concentrated magnetic sands, although 

these did not provide sufficient raw materials for the 

domestic steel industry 

In Czarist Russia, where the industrialization of 

the country as well as the development of ferrous and 

nonferrous metallurgy was not given sufficient attention, and where the wealth of a few individuals was 

5Translators' note: the Russian word "shlikh* has no exact English 

equivalent. It has been variously translated as heavy mineral, heavy 

concentrate, black sand. 
more important than the development of the country, 

it was natural that such techniques as the study of 

heavy minerals in prospecting were not used, and that 

there was no extraction of magnetic iron ore and other 

products from placers. It is true that some scientists 

connected with mining tried to direct the attention of 

miners toward the possibility of utilizing black sands 

commercially. But, since science in Russia at that 

time was ara low level of development, and this field 

did not promise great profit, the problem did not receive attention. In the last century, Ye. A. Taube 

and Abikh pointed out the possibility of exploiting the 

black magnetic sands along the coasts of the Black 

Sea for the needs of the Kerch metallurgical works. 

They also directed attention to the large deposits of 

magnetic sands along the seashores near Batum. 

K. I. Lisitsin noted the dark sands in the shores of 

the Azovskoye More [ Sea of Azov], which according 

to the investigations of. P. N. Chirvinskiy contained 

from 25.19 to 64. 52 percent magnetite. 

The recovery of magnetic iron from the black 

sands was not only attracting attention, but during 

the period of the imperialistic war, the question of 

processing rutile-bearing sands was raised. In 

Transbaikal in 1915, K. K. Matveyev investigated 

sands in which he found from 1, 2 to 55 percent TiO2 . 

The search for rutile also attracted attention to the 

monazite content of the sands. 

In this way, the problem of studying the mineralogical content of black sands and the method of 

separating them into their components became important. But the low level of Czarist science, inertia 

in working out the methods, and the absence of funds 

for scientific research, were a hindrance to the 

development of the studies of heavy mineral concentrates. 

However, in the Soviet State, a country conquered by the 

proletariat, the opportunities for placing scientific research on the highest level are great, and in this manner 

the wealth, hidden in the earth, is put at the disposal 

of liberated humanity. 

Each year the geological organizations send out 

many parties to explore for the needed nonferrous 

metals. But these explorations do not always bring 

satisfactory results. One of the reasons for this is 

the fact that the exploring parties are not sufficiently 

interested in the collection of black sands. In prospecting for rare minerals, especially in regions where 

outcrops are scarce, the heavy-mineral method is of 

great value. Using this as a reconnaissance-exploration method, we remove an element of uncertainty at 

a stage when the discovery of mineral deposits by 

geological methods is necessarily haphazard. This 

is why the heavy-mineral method has been of such 

great importance during the last five or six years. 

In the Soviet Union, the principles of heavymineral prospecting were established in 1927 at the 

initiative of the senior geologists of Central Scientificresearch Geologic-prospecting Institute, S. S. Smirnov 

and others, who, in introducing the problem, endeavored to establish the necessity for compiling heavy-mineral 

maps as a starting point in prospecting. But in the 

process of practical work it was apparent that heavymineral analysis not only formed a basis for exploration, 

but also put the question to the gold industry and to 

scientific research institutions, that heavy minerals 

from placer deposits might be utilized in industry. 

9 

In the gold placer and in black-sand deposits 

sampled by parties prospecting for nonferrous metals 

and rare earth elements, other minerals have often 

been found, which, in addition to the more abundant 

elements, could doubtlessly be used in industry. 

These minerals include: scheelite, wolframite, 

cassiterite, monazite, columbite, tantalite, zircon 

and others. Their abundance in black sands deserves 

the attention of the nonferrous and rare-elements 

industries. 

As early as 1932, A. Ye. Fersman pointed out that: 

"The rare elements, particularly tin, bismuth, 

tungsten, and to some extent molybdenum, tantalum 

and the rare earths, by the laws of geochemistry are 

derived from the final extracts of granitic magmas. 

They are often associated with gold, and therefore 

gold deposits as well as deposits of tin, tungsten and 

bismuth are associated with one another in areas of 

granite intrusives; during the erosion of granites, 

minerals containing these metals find their way into 

the black magnetic sands from which gold is commonly 

recovered. The old fashioned methods of gold mining 

were not concerned with these black sands, but in 

some of our districts these sands containing up to 

50 percent cassiterite constitute a source of this metal 

previously unexploited. Considering that up to 5000 

tons of black sands have passed through the gold sluices 

of Siberia, and that in some districts cassiterite is 

present in considerable quantities, as in northwest 

Pamir, the upper parts of the Kolyma and Indigirka 

rivers, and in the Kharginsk district at Selendzha, 

it becomes apparent that each year we have lost 

several hundreds of tons of valuable metals from these 

placers. Bismuth in addition to tin is found in gold 

sand (in the Kariysk district of Transbaikal), as well 

as monazite, which is the source of the rare earths 

and thorium (in the Undy and Kochkari district in the 

southern Urals), and in many places large quantities 

of wolframite ore, scheelite, and other minerals. 

The heavy minerals of gold placers, although they 

constitute a most valuable source of raw material 

for the entire rare-metal industry, have been poorly 

studied and have not been conserved as they are usually 

discarded after the gold is recovered. 

"One of the greatest tasks of our gold industry 

is to master this new problem in a technical and 

practical way in order to utilize all minerals that 

are contained in the placer deposits. " 

The presence of rare and precious minerals in 

our alluvial deposits necessitates widespread sampling 

and investigation of black sands, as well as development of equipment for the concentration and separation 

of heavy minerals. 

Heavy-mineral separation is not only a method 

for the winning of economic minerals, but is a 

guiding star in prospecting for nonferrous metals and 

rare earth minerals. In spite of the recency of its 

development, heavy-mineral analysis is of widespread importance in the U. S. S. R. today. For 

example, the data of P. S. Sasim in western Siberia 

show that in the two-year period, 1931-32, the 

application of heavy-mineral method in prospecting 

has resulted in the discovery of 500 monazite prospects, 

150 tungsten prospects, 50 cassiterite prospects, 30 
cinnabar prospects, 10 prospects of platinum and 

metals of the platinum group, and 8 fergusonite 

prospects. 

In central Asia several mineral deposits 

containing cassiterite, scheelite, columbite-tantalite, 

and other valuable minerals have been found by the 

heavy-mineral method. 

In 1933 in the central Zeysk mining district of 

the Far East, we found at "Bych'yem Klyuch" 175 

gold colors in a four-gram sample, and at the 

"Podgorny" mine, 112 gold colors in a 1.2-gram 

sample. 

If we consider that in neither case had the 

gold been sluiced, then it is reasonable that the 

source deposit is near the alluvial sands. Needless 

to say, these alluvial sands deserve attention. 

In 1927 in the northeast ,Transbaikal district, 

N. A. Khrushchev found black sands containing gold, 

bismuth, mercury, molybdenite, wolframite, 

scheelite, monazite, galena, and bismuthinite. 

The northern Caucasus district, where the 

black sands were sampled in detail, showed the 

presence of cassiterite over a large part of the 

district. 

An exploration of the Ural'skiy Khrebet [Ural 

Mountains] for the specific purpose of determining 

the extent of cassiterite in placer deposits showed 

that cassiterite is found in the Aydyrli, Gumerov, 

and Kochkar districts of the Yuzhnyy Ural; in the 

Alapayev district of the Sredniy Ural; and in the 

Severnyy Ural. Although this cassiterite does not 

occur in economic concentrations, its presence 

has enabled industrial organizations and geological 

trusts to undertake exploration for cassiterite 

using the new developments in prospecting technique. 

Valleys containing ancient alluvial deposits and 

Mesozoic terraces should be investigated with particular care. 

Investigations of river channels, ancient terraces, 

and also the more recent deposits should be carried 

out in the Soviet Union, because we are well aware 

that throughout the world, 80 percent of the cassiterite 

production is obtained from alluvial deposits, whereas 

the investigation of our alluvial deposits in the Soviet 

Union is far from satisfactory. 

All the ramifications of heavy-mineral analysis 

are not covered by the above article, but the data 

given should suffice to show that the heavy-mineral 

method ought to assume a leading role in the exploration for nonferrous-and rare metals, especially in 

poorly explored and sparsely populated regions. 

While the heavy-mineral method does not permit 

complete evaluation of the geology of a region, it 

will permit conclusions to be drawn regarding the 

type of rocks present, the character of the mineralization, and the economic importance of the mineral 

deposits. 

Types of Placers and the Paragenesis of 

Minerals in Black Sands 

Sands which result from the weathering of rock 

usually do not remain in place but are transported by 

water, wind or other agents. During transport they 

are sorted according to grain size and specific gravity. 

Uneven river bottoms and other causes tend to check 

the motion of the mineral grains. They settle and are 

sorted according to specific gravity, resulting in- the 

separation of valuable minerals. Concentrations of 

minerals in this way often constitute commercial ores, 

and are spoken of in industry as placers. According 

to their structure, placers may be classified as unconsolidated or as hard placers which have cemented 

and compacted into rocks, such as conglomerates. 

Placers can be classified according to origin as follows: 

Alluvial placers: Composed of pebbles, gravels, 

sands, and clays deposited by flowing waters. In the 

process of transportation the heavy and insoluble 

minerals are concentrated in the sands. 

Eluvial placers: Composed of weathered rock 

which has remained in place. 

Eolian placers: Composed of wind-deposited 

material in which the heavy-mineral particles are 

deposited not far from their sources. 

"Deluvial" placers: Composed of sediments 

deposited by waters flowing down mountain sides. 

Heavy-mineral particles are deposited either on 

mountain slopes or at the base of mountains. 

Diluvial placers: Composed of material derived 

from the erosion and crushing of rocks by glaciers. 

Marine placers: Composed of sands which have 

been formed and also enriched with heavy minerals by 

ocean waves and the tide. 

According to the data of V. I. Vernadskiy all 

these types of placer deposits have different characteristics and may be clearly distinguished in nature. 

The distribution of valuable heavy minerals varies 

within them. Thus, in eolian sands, they are found 

near the surface, where the finer particles are blown 

away; in alluvial placers they are found at the bottom 

where they have been disseminated in black sands by 

currents of flowing water. 

The association of minerals in sands does not 

represent a random collection of individual. components, 

having no relation to each other. At the close of the 

eighteenth and beginning of the nineteenth century, 

French and British mineralogists, such as Delille 

Hauy, Price, Jameson, and others developed the theory 

that the discovery of one mineral could lead to the 

discovery of others, because of their mutual association. 

A student of Werner named Breithaupt, who was 

the principal innovator of the study of mineral associations, combined the individual ideas and developed the 

theory of paragenesis. 

10 
"The doctrine of paragenesis is the basis of 

contemporary mineralogy. Only by an exact and 

complete study of paragenesis of minerals is one 

able to construct generalizations in this field of 

science. " The occurrence of one mineral serves 

as a guide to.others of possible economic importance. 

The association of minerals in sediments and 

placers enable one not only to determine the type of 

rock from which the mineral is derived, but also to 

predict, on the basis of theory, which other minerals 

will be found there. 

In this manner, the role of paragenesis in the 

study of alluvial deposits is just as important as it 

is in the study of minerals in primary deposits. 

Table 9 shows the accessory minerals and 

parent rocks associated with the valuable minerals 

of placer deposits (according to Milner). 

Although this table is not complete, it may be 

used as a guide to valuable minerals found in alluvial 

placers. 

By taking into account mineral associations in 

sedimentary materials, we have recently found new 

minerals in the black sands of the Ilmen forest 

preserve which up to this time were unknown in the 

mountains of Ilc-nen. These include cassiterite, 

cinnabar, native mercury, and platinum. It is true 

that the above-mentioned minerals were not of 

economic importance, but they deserve attention from 

the mineralogical and geochemical point of view, and 

the fact that they were discovered in placers once 

more emphasizes the importance of this method. 

Methods of Field Investigation 

The presence of rare and valuable minerals in 

sands presents prospecting and research organizations 

with problems of mass sampling and the determination 

of mineralogical content of placer material. First, 

the alluvial, eluvial and deluvial placers should be 

thoroughly sampled. Surveys of alluvial placers in 

our work were usually begun at the mouths of springs 

and rivers, including the tributary streams, if such 

were found on the way to the upper part of the river. 

Experience shows that a detailed investigation of a 

given district by the heavy-mineral method is possible 

only when the heavy-mineral samples are obtained 

from test pits. Black sands collected directly from 

the mouth of a river do not give satisfactory results 

with respect to the quantity and mineral content of 

the heavy concentrates. It is impossible to predict 

where to dig test pits, as this depends on the geologic 

conditions and the relief of the region. In practice we 

dug several test pits, spaced 20-25 meters apart along 

Table 9. -,,Gangue and country rock associated with placer deposits 

Group Ore 

minerals 

Gangue minerals Country rocks Remarks 

1 Platinum, iridium, 

osmiridium, 

palladium. 

Magnetite, chromite, 

 picotite, olivine, 

pleonaste, serpentine. 

Peridotite, basic gabbro, 

dunite, serpentine rocks. 

Presence of 

ultrabasic rocks 

may be an indictor. 

2 Gold. Pyrite, pyrrhotite, 

galena, chalcopyrite, 

concentrates rich in 

magnetite. Minerals 

of group 1. 

Quartz veins, associated 

with various igneous 

rocks. Conglomerates, 

granites (seldom). 

3 Cassiterite, 

wolframite, 

tantalite. 

Tourmaline, topaz, 

fluorite, monazite, 

scheelite, molybdenite, 

ilmenite, magnetite, 

lepidolite. 

Veins and ores, 

pegmatites, granites. 

Abundance of 

topaz, lepidolite, 

or mica with or 

without fluorite is 

an indicator. 

4 Diamonds. Ilmenite, serpentine, 

magnetite, chromite, 

picotite, pyrope, garnet, 

olivine. 

Basic igneous rocks, as 

peridotite; conglomerate 

(seldom). 

5 Corundum, ruby, 

sapphire. 

Amethyst, topaz, beryl, 

chrysoberyl, garnet, 

spinel, rutile. 

Crystalline dolomite, 

metamorphosed limestone, pegmatite, syenite. 

6 Monazite. Ilmenite, zircon. 

Minerals of group 5. 

Pegmatite, gneiss, 

granite. 

7 Emerald, 

chrysoberyl, 

alexandrite, 

garnets. 

Tourmaline, lepidolite, 

topaz, pyrite, spine', 

amethyst. Minerals of 

group 4 and 6. 

Granite, pegmatite, 

limestone, .gneiss, 

schists. 

11 
a line. If the valleys were wide, the distance between 

lines was 1.5-2 kilometers. In some valleys a grid 

of test pits was laid out at a spacing of 500-600 meters. 

In the test pits, 60-to 100-kilogram samples from each 

half meter of depth were collected and washed. It is 

very desirable that the geologist or prospector have 

first-hand experience with panning out the heavy minerals from the sample. Many investigators think that 

the method of obtaining the heavy concentrates is a 

simple matter, and trust the panning process to unqualified persons. Improper washing technique will 

give a distorted picture of the mineralogical content 

of the heavy concentrate because through carelessness 

a large part of the heavy components will be washed 

away with the lighter fraction. This will result in 

an incorrect evaluation of the placers, or will lead 

to incorrect conclusions in the course of prospecting 

an area for primary mineral deposits. 

The actual process of obtaining heavy minerals 

from placers was carried out with the following 

simple implements: an Asiatic pan, a so-called 

"koreysky" pan, and a washer. The pans are made 

of either thin sheet metal or wood; linden or poplar 

wood is best. 

The steel pan which we used in our work proved 

somewhat inconvenient, partly because of lower recovery of heavy minerals, and partly because the 

washing process is less convenient due to the small 

size of the handle. Wooden troughs are more convenient. They are usually 0.6-0.7 meter in length, 

0.3-0.4 meter in width and have a depth of 0.15-0.2 

meter. This size trough will hold from 12 to 16 

kilograms of rock. 

The trough is filled with rock and lowered into 

a pool of water which should be somewhat deeper than 

the trough (in running waters small excavations sometimes have to be made). The material in the submerged 

trough is broken up either by hand or, better still, with 

an iron rake. The large fragments are taken out for 

examination, and if barren are discarded. 

From time to time the trough is moved sharply 

back and forth, and again the material is loosened 

with the small rake. As a result,. the heavy particles 

settle to the bottom of the trough, and the light particles rise to the top and are carried away by the water. 

This concentration process is continued until only fine 

gravel remains in the trough. 

The operator then takes the trough, tips it 

slightly holding it on the surface of the water, turns 

it around with circular motions, shakes it, and 

lowers it in a tipped position into the water. By repeating these manipulations, he finally obtains a 

heavy concentrate at the bottom of the trough. 

In addition to the trough we have also used the 

Asiatic pan which seems to be preferred in the Ural 

Mountains, although in the Far East the prospectors 

all use troughs. The Asiatic pan is a simple iron pan 

with high edges and a flat bottom. Large Asiatic pans 

hold as much as 12 kilograms of rock. The process 

of washing sands with a pan does not differ much from 

the process of washing sands with a trough. The pan 

is filled with rock and lowered into the water. While 

one hand is holding the handle of the pan, the other 

hand shakes the opposite edge of the pan with rapid 

motions to the right and left, to break up the clots. 

12 

In order to loosen the material thoroughly, an 

iron scraper or hoe is sometimes used. The fine, 

heavy parts settle to the bottom, the light particles 

rise to the top and are carried away by the water. 

Clay and mud as well as fragments of various sizes 

are removed by means of a rotary stirring motion 

until a pure concentrate is obtained. 

In addition to the implements described above, we 

have also used an ore concentrator or washed in our 

work. We must add, however, that the washer was not 

used very often. It is useful in work at a more or less 

permanent camp where the object is to extract valuable 

minerals such as gold, platinum, iridium, and others. 

In exploration work, where the object is to determine 

the complete mineralogical content of black sands and 

to trace the distribution of minerals throughout an 

entire valley, as well as determine the mineralogical 

content of each individual test pit, an ore concentrator 

is not practical. However, washing with an ore concentrator is, of course, much more accurate than 

washing with a trough or pan. We have been using the 

ore concentrator exclusively for the purpose of determining the abundance of gold and platinum, and have not 

tried to determine the complete mineralogical composition of the heavy concentrates because even if we had 

found cassiterite, for example, in the concentrates, 

we could not trace its origin if the mill feed had come 

from different sources. To conduct a survey by taking 

the material to an ore concentrator for washing would 

require too much time and be very impractical. 

The heavy concentrates washed out by one of the 

above methods were dried either on paper in the sun, 

or over a fire in the same pan in which it was concentrated. A fire was used especially on cloudy and damp days. 

If cinnabar is present, the warming or drying must be 

done very cautiously to prevent it from volatilizing. 

The dried concentrate is placed into a 12x6 centimeter 

sample bag. A label is affixed to the sample bag to 

indicate the place from which the sample was taken, 

the number of the test pit, the quantity of material 

washed out in the troughs or pans, the date the sample 

was taken, and the name of the person who did the 

panning. 

To determine the genetic relation of heavy minerals 

to parent rocks, we have usually prepared artificial 

gravels; in the field, we have sampled country rocks 

as well as vein derivatives such as quartz, pegmatite 

veins, aplites, contact rocks and other vein phenomena. 

This enabled us not only to determine the genetic relationship, but also to study in detail the accessory 

minerals of intrusive and extrusive rocks. 

The rocks were crushed in a Blake crusher, and 

then ground to a size of 1 mm in a mortar. Not less 

than 25-30 kilograms of rocks were taken for crushing, 

and if the rock appeared important from a mineralization standpoint up to 50 kilograms were taken. 

In making a thorough investigation of the mineral 

resources, metallurgy, geochemical processes, mineralogy, geology, and petrology of an area, each investigator should apply the method of heavy-mineral 

analysis as well as the usual methods of study. Each 

geologist should be required to collect heavy minerals 

from both gravels and rocks. To show how informative 

heavy-mineral analysis canbe, we give in table 10 comparative lists of minerals reported in the literature and 

taken from our research on the heavy minerals in pits 
Table 10.--Comparison of minerals of the Ilinen forest preserve reported in the literature and those in heavy concentrates 

Pit No. 50 Pit No. 72 Pit No. 101 

Minerals inerals inerals 

Reported in 

literature 

Found in heavy 

concentrates 

Reported in 

literature 

Found in heavy 

concentrates 

Reported in 

literature 

Found in heavy 

concentrates 

Topaz Topaz Malacon Malacon Beryl Beryl 

Beryl Beryl Columbite Columbite Quartz Quartz 

Samarskite Samarskite Albite Feldspar Feldspar Feldspar 

Phenacite Phenacite Amazonite Quartz Smoky Quartz Biotite 

Monazite Monazite Quartz Limonite Cassiterite 

Garnet Garnet Corundum Topaz 

Malacon Malacon Muscovite Sphene 

Albite Topaz Pyroxene 

Feldspar Feldspar Zircon Hornblende 

Amazonite Sinets [ sic1 Tourmaline 

Biotite Biotite Rutile Zircon 

Ilmenite Ilmenite Magnetite Epidote 

Smoky Quartz Quartz Ilmenite Apatite 

Tourmaline Tourmaline Biotite Magnetite 

Onnerodite Muscovite Garnet Specularite 

}-, 

cz 

[ sicl Chlorite 

Hornblende 

Actinolite 

Cassiterite 

Epidote 

Pyrite 

Molybdenite 

Pyrite 

Muscovite 

Tremolite Tourmaline Garnet 

Wollastonite Hematite Ilmenorutile 

Pyroxene Hornblende Columbite 

Enstatite Sphene Pyrochlore 

Columbite Monazite 

Sphene 

Epidote 

Zircon 

Apatite 

Fergusonite 

Magnetite 

Ilmenite 

Pyrite 

Hematite 

Rutile 

Spinel 
number 50, 72 and 101 in the Ifmen forest 

preserve. 

This table shows that more minerals were 

tound in the heavy concentrates than had been reported 

before the application of heavy-mineral analysis. It 

is not reasonable to assume that the increased number 

of minerals found in the heavy concentrates from 

these pits was due to increments from other places, 

since the number of heavy minerals found in the sands 

is the same as the number of heavy minerals found 

in the crushed rocks from the same pits. The number 

of heavy minerals obtained from crushed rock will 

obviously exceed the number of minerals observed in 

a thin section of the same rock. 

The Study of Heavy Minerals in the Field 

Heavy-mineral concentrates ought to be studied 

on the spot in field laboratories, especially the 

economic deposits. The presence of an economic 

mineral enables estimation of its distribution and 

possible economic value. Modern prospecting for 

important economic minerals such as cassiterite, 

wolframite, scheelite, galena, silver, gold, and 

others, requires a small portable laboratory for 

each prospecting geologist and research scientist. 

Reaction tests for the minerals mentioned above are 

simple and do not require complicated equipment. 

After returning from the expedition, detailed analysis 

of the entire mineralogical content of the heavy 

concentrates is made by means of separate processes. 

Under field conditions it is not necessary to 

make a complete separation of the sample into 

constituent minerals but for rapid examination of 

heavy minerals, a rough separation may be made. 

The magnetic fraction may be separated with a 

simple horseshoe magnet, and the electromagnetic 

fraction may be separated by a field electromagnet, 

with which 15 fractions can be obtained. 

The field electromagnet weighs 8-10 kilograms. 

It does not require an external electric circuit, but 

is charged by flashlight batteries. We will not give 

a detailed description of this magnet, since in 

principle it is similar to the electromagnet described 

in detail below. 

Minerals such as scheelite, casserite, zircon, 

rutile, galena and others remain in the nonelectromagnetic residual fraction, and are determined 

comparatively easily in the field. In order to detect 

scheelite, which has often gone undetected under 

field conditions, G. Komovskiy and F. Abolenskiy 

constructed a portable device with an ultraviolet 

lamp which enabled them to detect scheelite by its 

light blue radiation. It is true that diamonds give a 

light blue fluorescence, but these two minerals are 

never confused, even by individuals who know little 

of mineralogy (see p. 212-213). 

There is no doubt that this device will be widely 

used in investigations of many regions. In field 

practice it provides us with the only indicator for 

scheelite, which by the other methods could be 

overlooked. 

14 

These devices are manufactured by the mechanical 

workshops of the Institute of Geological Sciences, Academy 

of Science. Another device invented by G. Komovskiy 

to detect scheelite, zircon, diamonds and -other minerals 

by their radiation properties, is the field cathode unit. 

This device is very useful in the field. 

It consists of a hand-driven vacuum oil pump, 

a flywheel which drives a 15-kilowatt generator with 

a belt, and a cathode tube with a hose connection to the 

vacuum pump. The material to be examined is placed 

in the cathode tube. The hand-driven flywheel pumps 

out the receptor until maximum vacuum is obtained. 

If the specimen contains scheelite, it will be easily 

detected.by its intense light blue radiation. This unit 

is manufactured by the same organization mentioned 

above. There is no doubt that both of these devices will 

be of great help to the prospector and research worker in 

their practical work. 

Sometimes it is necessary to examine minerals 

and rocks for radioactivity in the field. The sample 

to be examined may be placed in the receptacle of an 

electroscope. The electroscope is charged by an 

ebonite rod. The amount of radioactivity of the given 

sample is determined by the rapidity with which the 

"leaves" fall in the electroscope. (See page 228). 

The Separation Process 

To speed up the processing of heavy-mineral 

concentrates, the following chart has been worked out 

on basis of practical experience (fig. 46). The heavy 

concentrate, which has been collected at some prospect 

in the. field, is weighed, and if too large is reduced by 

quartering. This is done by mixing, spreading on 

paper, and dividing into four equal parts; if it appears 

that the quarter remaining is larger than what is required for examination, the process is repeated. 

We have used 25-gram portions (or less if that 

much were not available) of heavy-mineral concentrates 

for examination. Usually, after obtaining an average 

sample, the magnetic minerals were extracted with a 

horseshoe magnet as follows: The magnet was held 

over a layer of the sample grains spread out on glass; 

the poles of the magnet were either covered with pape r 

or were simply separated by a sheet of clean paper 

from the sample. The highly magnetic minerals would 

stick tc the paper at the poles of the magpet, and could 

be deposited on a separate sheet of paper. This process 

was continued until all magnetic minerals were extracted. 

Very often nonmagnetic minerals are extracted 

along with the magnetic ones, and the above method 

must be repeated to eliminate the nonmagnetic minerals. The magnetic fractions are weighed and poured 

into small packages which are labeled as follows: 

Magnetic fraction, Cheremshanka district, prospecting 

pit no. 2. 

The remaining nonmagnetic fraction is passed 

through a number of standard sieves, in order to 

obtain fractions of uniform size. This permits a more 

complete electromagnetic separation of the minerals. 

The coarse fraction obtained from the sieving is weighed, 

labeled and sent to the mineralogist for further examination. The remaining nonmagnetic fraction is 
Heavy mineral 

concentrate 

Averaging 

process 

Magnetic 

separation 

Less than 

2 mm 

Figure 46. --Diagram of separation processes 

Magnetic 

fraction 

Mineralogic 

investigation 

Greater than 

2 mm 

Separation 

by bromoform 

Nonmagnetic 

fraction 

Sieve analysis 

Mineralogic 

investigation 

Light 

fraction Heavy fraction 

Mineralogic 

investigation 

Electromagnetic 

separation 

Electromagnetic 

fraction 

Nonelectromagnetic 

fraction 

Mineralogic Mineralogic 

investigation investigation 

15 
placed in a funnel containing bromoform. The minerals 

which have a higher specific gravity than the bromoform 

(2.9) settle to the bottom of the funnel, and the minerals 

with a lower specific gravity rise to the top. The extracted light fraction is labeled and then submitted for 

a mineralogical analysis. The heavy fraction is further 

concentrated into constituent minerals by the electromagnet. In our work, only bromoform was used as a 

heavy liquid, but often there is a need for liquids with 

specific gravity greater than bromoform, such as: 

1. Methylene iodide, CH2I2, specific gravity: 

3. 3. Next to bromoform this is the most suitable 

solution. It has a lavender-red color and like bromoform it disintegrates in light, becoming brown. 

2. Sushin-Rohrbach solution, composition: 

Ba12 + HgI2+ H2O specific gravity: 3. 5. 

3. Mercuric nitrate, specific gravity: 4. 3. 

A poisonous compound, solid at room temperature, 

becomes liquid at 70 C. 

4. Thallium-silver nitrate, TlAgN206,flux 

with a melting point of 75 C, specific gravity: 4.8. 

Very soluble in water. Is used in liquid form, whereby 

the heavy fraction sinks to the bottom of the vessel, 

and the light fraction rises to the top. When it 

solidifies the upper and lower parts of the solid flux 

may be cut apart, and the minerals are obtained by 

melting these parts of the flux in water. 

5. Thallium-mercury nitrate, T1HgN206, 

specific gravity: 5. 3, fuses at 76 C. It is used 

chiefly for the separation of ilmenite, magnetite, 

pyrrhotite, pyrite and monazite from the minerals: 

columbite, scheelite, wolframite, and cassiterite. 

All of the above mentioned fluxes and solutions, 

especially numbers 1, 3 and 5, should be stocked by 

heavy-mineral laboratories, particularly where a 

complete mineralogical determination of heavy minerals 

is made. The separation of the heavy fraction from 

the light with bromoform is well known, and will not 

be described here. 

The residue obtained from the bromoform 

separation is separated into constituent minerals by 

an electromagnet. This facilitates further determinations of mineral content. We have used an electromagnet manufactured by the magnetic laboratory of 

the State university of Moscow, and designed by the 

director of that laboratory, N, S. Akulov. 

The electromagnet has a rectangular core of 

soft transformer iron, 42 centimeters on a side with 

a cross section of 9. 5 x 9. 5 centimeters. One side of 

the core is wedge-shaped and forms one of the poles 

of the electromagnet. The angle between the edges of 

the wedge is 45 degrees. The other pole of the electromagnet is a square plate 10 x 10 centimeters and 2 

centimeters thick. This plate is fixed directly under 

the wedge. The dimensions of the core are such 

that two coils can be wound upon it. The second coil 

can be used either to increase the field or to demagnetize 

it. The main coil has 1700 ampere turns of P. B. D. 

[ sic] wire, diameter of 1. 5 mm. The weight of the 

wiring with its insulation is 16. 5 kilograms. The 

winding consist of two parallel sections, each having 

independent connections, which enables one to unite 

them in either series or parallel. The height of 

the coils is 28 centimeters. The coil is fed by 

7 to 8 ampers direct current. Because we 

had to use alternating current, we used a motor generator set for rectification. The electromagnet, of course, 

was equipped with an ammeter and sliding-contact 

rheostats. The rheostats enabled us to regulate the 

strength of the current and to determine in this manner 

what current strength attracted certain minerals. 

One of the best features of N. S. Akulov's electromagnet is the fact that the wedge-shaped bar enables 

one to obtain the largest gradient of the magnetic field. 

With this electromagnet we could frequently obtain 

completely pure mineral fractions of titanite; monazite, 

ilmenite, hornblende, garnet, and others. However, 

some of the fractions contained impurities of other 

minerals, which can be attributed to insufficient calibration of our electromagnet, and the absence of a second 

coil. 

The separation was carried on in the following 

maxiner: the current was turned on; beneath the pole 

of the vertical wedge-shaped bar a glass was placed on 

which a thin layer of heavy minerals was spread. The 

glass with the sample was placed upon the square plate. 

The distance between the poles was regulated by a 

screw, which lowered and lifted the wedge-shaped bar. 

The sliding-contact rheostats enabled us to regulate 

the strength of the current and to find out what current 

strength attracted which mineral. The stationary plate 

allowed us, without the slightest jarring, to move the 

glass slide with the sample in different directions 

beneath the point of maximum field strength of the 

north pole of the wedge-shaped bar. The electromagnetic 

particles of the sample are attracted by the north pole 

and distributed in a uniform layer on the sharp wedge. 

After the pole has gathered all the electromagnetic 

minerals for a particular current strength, the glass 

is removed and replaced by a clean sheet of white 

paper. The grains which are clinging to the north pole 

of the electromagnet fall on the paper after the current 

is switched off. Some of the grains, owing to remnant 

magnetism, remain on the sharp edges, and have to be 

removed with a brush. 

In order to be sure that no minerals remain which 

are capable of being attracted by the electromagnet for 

a given current strength corresponding to a given distance 

between the poles, this operation is repeated several 

times until electromagnetic grains are completely extracted under the given conditions. The electromagnetic 

fraction extracted in this manner is weighed, labeled 

and sent to the mineralogist for examination. The 

remaining part of the electromagnetic fraction is 

subjected to a similar process with a corresponding 

change of current strength and the distance between the 

poles. With the aid of the electromagnet described 

above we have been able to obtain up to 15 mineral 

fractions from heavy residues. This has considerably 

facilitated the mineralogic analysis of the sediments. 

The results of our experiments upon the electromagnetic 

separation of different minerals and their tendency to 

be attracted by the electromagnet as a function of the 

distance between poles are listed in table 11. 

16 
Table 11. --Electromagnetic data for the separation of minerals 

No. Name of 

Mineral 

Distance 

between 

poles in mm 

Current 

Strength 

in amperes 

No. Name of 

Mineral 

Distance 

between 

poles in mm 

Current 

Strength 

in amperes 

, 

1 Ilmenite 5.0 24 Actinolite 2.0 

} 11 

2 Rhodonite 6.2 25 Arfvedsonite 2.2 

3 Spessartite 2.3 26 Pyrope 2.4 

> 7 

4 Hornblende 4.0 27 Ilmenorutile 3.0 

5 Biotite 4.2 28 Monazite 3.2 

6 Andradite 4.4 29 Diopside 7.0 

9 

7 Hedenbergite 4.6 30 Enstatite 4.0 

8 Bustamite 5.3 31 Blomstrandine 

, 

4.2 

9 A ugite 5.5 32 Wollastonite 6.2 

6.5 

10 Columbite 6.5 33 Uralite 6.7 

11 Almandite 1.6 34 Cassiterite 0.5 

12 Hypersthene 1.9 35 Sphene 1.5 

13 Fergusonite 2.0 36 Cuprite 6 2.5 

14 Ural-orthite 2.3 37 Thorite 5.0 

15 Scapolite 2.6 38 Pyrochlore 7.0 

16 Epidote 2.8 39 Malacon 2.5 

8 

17 Samarskite 3.5 40 Beryl 3.8 

18 Tantalite 4. 0 41 Corundum 7.0 

5.5 

19 Chromite 5.0 42 Orangite 2.0 

20 Olivine 6.3 43 Tremolite 4.0 

21 Spinel 6.4 44 Aeschynite 5.0 

22 Chevkinite - 45 Tourmaline 5.6 

(clear) 

23 Euxenite 7 1.0 

17 
Figure 49. --Mineral Determination Diagram 

Heavy 

Minerals 

Mineral 

habit 

Crystallographic 

system 

Color Structure 

Behavior 

under 

blowpipe 

Behavior 

in open 

& closed 

tube 

Borax and 

phosphate 

bead test 

Specific 

Gravity 

Optics 

Transparency Pleochroism Angle of 

extinction 

Optic 

axial 

angle 

Optic 

sign 

Color 

Mineralogical Analysis 

Spectral analysis 

Binocular Microscope 

Subsequent stage 

of determination 

Luster Fracture Cleavage 

Hardness Streak 

Ti Test PO4 Test Ce, Th 

Test 

Nb, Ta 

Test 

Te, Mn 

Test 

Sn test 

18 
Determination of the Mineral Content of 

Heavy Concentrates 

The successive separations yield these products: 

magnetic fraction, nonmagnetic fraction of grain size 

greater than 2 mm, light fraction, electromagnetic 

fraction, nonelectromagnetic fraction. 

After these separations have been made, the 

mineral composition of the fractions is studied with 

the binocular microscope and blow pipe. A preliminary 

examination was performed with these two instruments, 

and if there was doubt regarding a certain mineral, 

additional methods of identification were used. (Diagram 

49) Mineral determination by means of the binocular 

microscope involved study of its external form and 

physical properties, that is, the external appearance 

of the mineral, its crystallographic form, color, 

luster, fracture, cleavage and structure. 

If these procedures were insufficient to determine 

the mineral, it was tested by Moh's scale of hardness; 

the color of the streak was determined; a blow pipe 

analysis was made; the specific gravity was determined; 

and M rare cases, goniometric measurements were 

taken. 

Besides these procedures we often used the 

immersion test, which was of great help in identifying 

the transparent minerals. This test consists of the 

following procedure: The unknown mineral is transferred to a microscope slide with a watercolor brush 

or a needle. If the grain is too large, it is crushed 

either on the slide or in an agate mortar. The fragments are put under a cover glass beneath which is 

placed an immersion liquid with an index of refraction 

close to that of the mineral. If the index of refraction 

of the liquid is larger or smaller than that of the mineral, it is removed from the slide with filter paper 

and replaced by another liquid. Frequently, when 

withdrawing the liquid from the slide; the fragments 

are drawn to the edges with the liquid, so that either 

the cover glass has to be shifted or another grain 

taken. To avoid this, place the fragments in a drop 

of water on the slide so that after evaporation the 

fragments stick to the slide. 

Microscopic analysis is used to determine 

pleochroism, color, dispersion effect, angle of 

'extinction with respect to its elongation or cleavage, 

and the optic sign. Similarly the "osnost", the 

principle optical axis arid optic sign, of the mineral 

were determined with a no. 7 objective. For determining minerals whose indices of refraction were higher 

than our solution (1. 783), we used fusions. Sometimes simple microchemical analyses were made, 

especially to determine the rare earth and opaque 

minerals. 

Spectroscopic analysis was used to determine 

minerals of doubtful identity, which frequently include 

rare earth minerals. 

Fluorescence of minerals was determined with 

a stationary cathode-ray unit, consisting of a cathoderay tube and a screen. This apparatus, designed by 

G. Komovskiy, permits the luminiscence of minerals 

to be observed through a pane of glass by means of 

magnifying devices such as the microscope or the 

binocular lens. The cathode-ray tube and screen 

19 

was large enough to allow not only small objects to 

be irradiated, but lumps of ore as large as 10x10x3 

centimeters. For further description of the cathoderay apparatus, reference is made to the work of 

G. Komovskiy and F. Abolenskiy, published in the 

journal "Soviet Geology", 1938, No. 4, pp. 207-214. 

To detect scheelite in hand specimens and heavy 

concentrates we used the stationary ultraviolet-ray 

apparatus at the Institute of Geological Sciences, 

Academy of Science. 

Determination of Heavy-Mineral 

Content of the Sample 

The percentage of heavy minerals in sedimentary 

material is proportional to the ratio of weight of the 

heavy minerals to the weight of the original sample. 

This determination demands extreme care because of 

loss of part of the heavy minerals in washing. We 

determined the percentage yield of each particular 

mineral as follows: with the help of an intergrating 

stage, by the ratio of the weight of the particular mineral 

fraction to the total weight of the heavy minerals; 

by a count of the individual grains in each fraction. 

In order to make a quantitative calculation of 

luminescent minerals, E. Razumna suggested the 

following: luminescent analysis by means, of a 

comparison standard; luminescent analysis by means 

of the zero point method of calculation. 

Widespread mapping of heavy mineral concentration will better reveal the extent of economic 

placer deposits, and will add to the knowledge of 

halos of dispersed metals about primary ore deposits. 

In his paper upon exploration for rare metal 

deposits in Siberia, F. N. Shakhov describes in 

detail the character of the heavy mineral assemblage 

in relation to the type of sands, the method of obtaining heavy mineral concentrates, and the method of 

compiling the heavy mineral map, that is, plotting 

the geochemical as well as the mineralogic data on 

the geologic map. 

Similar large scale investigations, especially 

in the Ural Mountains and in western Siberia, show 

that, by compiling accurate maps of heavy minerals 

and contouring so as to indicate places of maximum 

concentration for each element or mineral, areas 

which require futher exploration may be selected. 

By study of the typomorphic characteristics of 

crystals, the presence of definite genetic types of 

primary deposits may be revealed. 

Heavy-mineral maps of river systems allow 

one to determine those tributaries which drain regions 

containing primary mineral deposits. 

Bibliography 

Abikh, Mestorozhdeniye magnitnogo zheleznyaka na 

beregu Chernogo moriya [Deposits of magnetic 

iron on the shores of the Black Seal: Gorn. zhurn, 

1856, ch. 3. 

Bazhenov, K., Promyvka shlikhov [The washing of 

heavy minerals', Izd. Zap. -Sib. geol. -razved. 

trudy, Tomsk, 1932. 
Bilibin, Yu. A., Osnovy geologii rosspey [The basic 

geology of placers], GONTI 1938, pp. 487-496. 

Voprosy issledovania shlikhov [Problems of 

investigating heavy minerals]: Mat. soveshch. 

Glavgeol. v Inst. Miner. syr'ya 14-16/IV, 1936, 

ONTI 1937. 

Voronova, Ye. A. and Zeeman, G. V., 0 metodike 

issledovanya shlikhov [ On methods of investigating 

heavy minerals]: Izv. Vses. Geol.-pazv. ob"yed., 

1931, vyp. 64. 

Zeeman, G. V. and Lur'ye, M. L., Instr. po sostavleniyu 

shlikhovykh kart [Instructions upon the compiling of 

heavy mineral maps]: Tsentral'. nauch. - issledov. 

geol. -razved. inst., 1938, pp. 1-48. 

Igumnov, A. N., Izucheniye mineralogicheskogo sostava 

ural'skikh shlikhov (Studies of the mineralogical 

composition of Ural heavy minerals): Izv. Vses. geol. - 

razv. ob"yed, 1931, vyp. 64. 

Komovskiy, G. and Abolenskiy, F., Lyuministsentsya 

mineralov i apparatura dlya ee issledovaniya [The 

luminescence of minerals and apparatus for its 

investigation]: Probl. sov. geologiya., 1938, No. 4. 

Lozhkin, V. V., Polevoy mineralogicheskiy analiz 

[Mineralogical field analysis]: ONTI, Moscow, 1937. 

Matveyev, K. K., Ob"yasnitel'naya zapiska po voprosu 

o titanovykh rudakh v shlikhakh [Explanatory notes 

upon the problem of titanium ores in heavy concentrates]: Trudy. Komiss. syr'ya, vyp. 1. 

Nikitin, D. V., Metody poiskovykh i razvedochnykh 

rabot v rossypyakh [ Methods of prospecting in alluvial 

deposits]: Tsentral'. nauch.-issledov. geol.-razved. 

inst. 1932, pp. 1-10. 

Odinets, Kak vesti shlikhovoye oprobovaniye redkikh 

mineralov [How to carry out sampling of heavy 

concentrates for rare minerals]: Sov. krayevedeniye 

[ Soviet regional studies], 1936, No. 6. 

Sasim, P. S., Metodika sbora i obrabotka shlikhov 

[Methods of collecting and processing heavy concentrates]: Izd. Zap.-Sib. geol. rasvedtrudy,Tomsk. 1934. 

Sasim, P. S., Metodika sbora shlikhov [Methods of 

collecting heavy minerals: Razvedka nedra., 1936, No. 17. 

Serdyuchenko, D. P., Otkrytiye olova na Severnom 

Kavkaze v svyazi s mineralogo-khimicheskim 

izucheniyem shlikhov [The discovery of tin in north 

Caucasus in connection with mineralogical-chemical 

studies of heavy minerals]: Uchen. zap. Rostov-Donsk. 

univ., 1935, vyp. 3. 

Sigov, A. P., Promyvka shlikhov pri geologo-razvedochnykh 

rabotakh [The washing of heavy minerals during 

geological-survey operations], Sov. zolotoprom. , 

1937, No. 3. 

Schlikhovye izyskaniya [Heavy-mineral studies]: 

Trudy nauch. -issledov. inst. Sverdlovsk, 1939, 

4, pp. 1-64. 

Fersman, A. Ye., Perspektivy rasprostraneniya poleznykh 

iskopayernkh na territoriiSoyuza[Aspects of the 

distribution of mineral deposits in the Union], Akad 

Nauk, Izd. 1932. 

Flerov, B. L. , Primeneniye olovometricheskoy 

s"emki pri poiskakh korennykh mestorozhdeniy 

olova [The application of stannometric survey to 

prospecting for primary tin deposits]: Redkiye 

metally, 1935, No. 1. 

Khrushchev, N. A., Materialy po izucheniyu poleznykh 

iskopaemykh severo-vostochnogo Zabaykal'ya 

[Data from the study of the mineral deposits of 

northwestern Transbaikall: Gl. geol. -razved, upr., 

1931, vyp. 90. 

Chuyeva, M. N., Shlikhovoy analiz [Heavy mineral 

analysis]: Tsentral'. nauch. -issledov. geol. - 

razved. inst., Izd. 1937. 

Shakhov, F. N. Poiski mestorozhdeniy redkikh 

metallov v Sibiri [Exploration for deposits of 

rare minerals in Siberia]: Zap. -Sib. geol. 

trudy, Izd., Novosibirsk 1937. 

The Necessary Instruments and Reagnets for Field Work 

Blowpipes 2 

Platinum wire 3 

Horseshoe magnet 1 

Scale of hardness 1 

Hand lens 1 

Binocular lens 1 

Collection sieve 

Alcohol lamp 2 

Candles 

Brushes (assorted sizes) 5 

Zinc plates 3 

Porcelain plates 3 

Gypsum plates 3 

Microscope slides 1 carton 

Test tubes 25 

Capillary tubes 

Porcelain mortars 2 

Scissors 1 

Pipettes 10 

Hammer with anvil 1 

Watch glasses 10 

Pocket knife 1 

Pincers 3 

Scale with weights 1 

Chemical glasses 10 

Medium-sized funnels 5 

Potassium nitrate 100 g 

Nitric Acid 500 g 

Br omoform 500 g 

Borax 100 g 

Denatured alcohol 3 kg 

Granular tin 200 g 

Ammonium molybdate 100 g 

Hydrogen peroxide 200 g 

Hydrochloric acid 500 g 

Sodium carbonate 100 g 

Sulfuric acid 500 g 

Phosphate 100 g 

Zinc dust 200 g 

20 
SPECTROSCOPIC METHODS collimating type; a diagram of the instrument is 

By S. A. Borovik. given in Figure 52. 

Spectroscopic analysis is important for determination of valuable metals. Gallium, indium, germanium, 

and rhenium are usually found in concentrations measurable only by the spectroscope. Spectroscopic analysis, 

also, has a large number of advantages in the determination of other elements. 

The work of Gramont, Hartley, Pollock, and 

lately, Gerlach Scheibe, and Mannkopff, has brought 

quantitative spectroscopic analysis to an accuracy 

closely approaching that of the best chemical methods 

and exceeding them in sensitivity. 

The chief advantage of spectroscopic analysis is 

the speed by which results are attained. Under 

favorable conditions an accurate quantitative analysis 

of an unknown sample may be made in 5 to 10 minutes. 

This is especially valuable in geochemical surveys 

because it enables the number of analyses to be increased ten to twenty times. The field work done by 

the spectroscopic laboratory in Khapcheranga and in 

Khalilov confirms this statement. 

Recently, the State optical institute constructed 

a special type of spectrograph to be used in the field. 

This spectrograph is a small instrument of the selfIn the field spectrograph the light from the 

arc (1), where the sample is placed falls on the 

slit (2) and then reaches the quartz prism (3). It 

is reflected at right angles and falls on a quartz 

lens (4). After passing through the lens, the light 

falls in a parallel beam on the sylvite prism (5), 

is reflected from the silvered top, and returns 

through the same lens (4). Passing through the 

prism (3) the beam of light forms the image of the 

spectrum in the focal plane (6) of the optical system 

where the photographic film is placed. A diagram 

of the electric arc circuit is shown in Figure 53. 

An overall view of the instrument is given in Figure 54. 

This apparatus was used chiefly for determining 

t in. Prokof'yev and Islamov have developed a method 

which they call "the method of the emergence of line. " 

A sample is ground to 200 mesh and placed in a 

carbon electrode with a cup 2 mm in diameter and 

4 to 5 mm deep. This electrode serves as an anode 

and is placed at the bottom. Another carbon rod with 

a cone-shaped tip is fastened above and serves as 

the cathode. The authors who devised this method 

give the following table for finding the concentration 

of tin (Table 12). 

Table 12. --Spectral lines used for quantitative analysis of tin 

Tin concentration (percent) Lines and their characteristics 

Considerably less than 0.05 (order of The line 2429. 5 is present. In comparison with 

magnitude of thousandths of a percent) the lines of the surrounding structure, it is 

weaker in its intensity. 

Less than 0.05 (order of magnitude of The line 2429. 5 is present. In its intensity it 

hundredths of a percent) does not differ from the lines of the band 

structure. 

0.05 The line 2429. 5 is clearly visible, weak lines 

of 2546. 5, 2421. 7 and 2317. 2 are slightly 

visible. 

0. 1 Line 2421. 7 is clearly visible, weak lines 2571. 6 

and 2334. 8 as well as a slight image of line 

2786.0 are visible. 

0. 2 A scarcely noticeable line 3032. 8 is visible 

0. 3 Line 3032.8 becomes more visible. Very slight 

images of lines 2317. 2, 2913.5 and 2408. 2 

become visible. Lines 2594.4 and 2850.6 are 

very clearly,seen. 

1.0 A suggestion of line 2813.6 is visible. Lines 

2408. 2, 2913. 5 are weak but clearly seen. 

3.0 Very weak lines 2331 appear. Line 2455. 9 

becomes much more distinct in comparison 

with the intensity of the nearest line of the band 

structure. 

10.0 Line 2408 becomes clear. Very weak line 2268 

and weak line 2558.0 appear. 

21 
Experience shows that this table may be used for 

determining tin in samples of widely different compositions. This is done by adhering strictly to the same 

conditions of exposure, development, and sensitivity of 

plates that were used in preparing this table. 

The sensitivity of the perforated negative film 

for the F. E. D. [sic] Isopanchrome is 700. Eight 

ampers were supplied to the arc; the exposure time 

was 60 seconds. Carbon rods of the make "Extra" 

which have a diameter of 10 mm were used. 

When starting one should check on the working 

conditions to see how they affect the relation between 

the emergence of the line and the concentration of tin. 

Samples were made up with known tin concentrations and 

spectrographed. If a discrepancy was noticed; the 

necessary corrections were made in the table. Consequently,' the consecutive emergence of the lines 

remains the same. 

However, a complete separation of lines is not 

obtained with the field spectrograph of the National 

Optical Institute (GOI). If elements other than tin 

have to be determined, then the Hilger spectrograph 

is better, especially the large model. If that one is 

not obtainable a medium-size model can be used. 

In Table 13 we list elements which can be detected 

with these spectrographs. 

The sensitivity for most of the elements listed 

is 0.001-0.01 percent. A sensitivity of 0.0001 percent 

can be obtained for Cu, Ca, Sr, Ba, Mg, Al, and Ag. 

However, P, As, Te, B and C are sensitive to only 

0.1 percent and can be determined only in copper 

electrodes. The carbons should be purified by 

roasting them with a current density of 20 amperes 

per square millimeter. 

These methods require 220 or 110 volts and 

8 to 12 amperes, which limits their use under field 

conditions. 

Lundegardh has worked out a method which does 

not require an electric current; it uses an oxyacetylene 

flame. Figure 55 shows the device used by Lundegardh. 

The sample is dissolved (3 to 10 ml) and then vaporized 

by a stream of air. The vapor is passed through a 

nipple and mixed with the oxyacetylene in a glass 

tube before entering the burner. The burner has 

a quartz tip and a platinum screen to keep the flame 

from backfiring. The flame is placed directly before 

the quartz slit of the spectrograph. 

By means of this method the following elements 

can be detected: Ag, Au, Ba, Ca, Cd, Co, Cr, Cs, 

Cu, Fe, Hg, K, Li, Mg, Mn, Na, Ni, Pb, Pd, Rb, 

Ru, Sr, Tl. 

The sensitivity of the flame spectroscope is 

considerably less than the electric arc. 

When a high-temperature oxyacetylene or oxyhydrogen 

flame is used, one is able to obtain spectrograms 

of minerals by placing a powder of the mineral, 

wrapped in ash-free filter paper (Ramedge) in the flame. 

Table 13. --Wave lengths of elements detected in the carbon arc 

Element Wave length of the most 

sensitive lines in g 

Element Wave length of the most 

sensitive lines in A 

Ag --- 3382. 9; 3280. 7 Mo --- 3798. 3; 3864. 1; 3132. 6 

Al --- 3961. 5; 3944.0; 3092. 7; 3982. 2 Na --- 3302. 3; 5890. 0; 5895. 9 

As --- 2349.8; 2288. 1; 2789.2; 2860.5 Nb --- 4059.0; 4079; 3580; 4101 

Au --- 2676.0; 2428.0 Ni --- 3524. 5; 3414. 8; 3619. 4; 3050. 8 

B --- 2497. 7; 2496. 8 Os --- 2909. 1; 3058. 7; 3301. 6 

Ba --- 4554. 0; 4934..1; 5535. 5 P --- 2535. 6; 2553. 3; 2534. 0; 2554. 9 

Be --- 2348. 6; 3130. 4 Pb --- 4057. 8; 3683. 5; 2833. 1 

Bi --- 3067. 7; 2898. 0; 2938. 3; 2989. 0; Pd --- 3404. 6; 3634. 7; 3609. 6 

3024. 6 P --- 3064. 7; 2659. 4; 2998. 0 

C --- 2478.6 Ra --- 3814.4 

Ca --- 4226. 7; 3933.7; 3968. 5 Rb --- 4201. 8; 4215. 6; 7800.3; 7947.6 

Cd --- 2288.0; 3261. 1; 3610. 5; 2265.0; Re --- 3460. 5; 3464. 7; 3451. 9 

2144. 4 Rh --- 3434. 2; 3692. 4 

Ce --- 3801. 5; 4186. 6; 3560. 8; 4133. 8; Ru --- 3728. 0; 3799. 3; 3499. 0; 3436. 7 

4137. 6 Sb --- 2598. 1; 2528. 5; 2877. 9 

Co --- 3453. 5; 3405. 1; 3502. 3; 3412. 3 Se --- 3613. 8; 3630. 8; 3572. 6 

Cr --- 3578. 7; 3593. 5; 3605. 3; 4254 Si --- 2881. 6; 2516. 1; 2506. 9 

Cs --- 4555. 3; 4593.2 Sn --- 3175; 2840; 3034 

Cu --- 3247. 5; 3274. 0 Sr --- 4077. 7; 4215. 5; 4607. 3 

Fe --- 3581. 2; 3719. 9; 2483. 3; 3020. 6 Ta --- 2714. 7; 2653. 3; 2647. 5 

Ga --- 4172. 1; 4033.0; 2943. 6; 2874. 2 Te --- 2385. 8; 2383. 3 

Ge --- 2651. 2; 3039. 1; 2754. 6 Th --- 2837. 3; 3741. 2; 4019. 1 

Hg --- 2536. 5; 3650. 2 Ti --- 3349. 4; 3361. 2; 3234. 5 

In --- 4511. 3; 4101. 8; 3256. 1; 3039. 4 Tl --- 3775. 7; 3519. 2; 2767. 9 

Ir --- 3220. 8; 2924. 8; 3133. 3; 2849. 7 V --- 3184.0; 3185. 4; 4118; 3093.1 

K --- 4 044. 2; 4047.2 W --- 2944.4; 2947.0; 4008.8 

Li --- 4603. 2; 3232. 7; 4132 Y --- 3710. 3 3600. 7; 3774. 3 

Mg ---- 2852. 1; 2795. 5; 2802. 7 Zn --- 2138. 5; 3345. 0; 3302. 6 

Mn --- 2794. 8; 2798. 3; 2801. 1; 4030. 8 Zr --- 3392. 0; 3438. 2; 3496. 2 

22 
This method requires, of course, two steel cylinders 

equipped with reducing valves to Contain the oxygen 

and acetylene or hydrogen. The lines of those elements which are most easily excited, such as Rb, Cs, 

Ca, Sr, Ba, In, Tl, Li, Na and K, may be observed 

in the flame of a Bartel-type gasoline lamp. 

Placing the mineral sample directly into the 

oxyacetylene or the oxyhydrogen flame usually fails 

to produce a spectrum. If the easily excited elements 

listed above are present in the sample, they should 

be changed into compounds that vaporize easily. A 

small amount of the sample is powdered and mixed 

with hydrochloric acid. A fine bent platinum wire 

is dipped in the resulting solution and placed in the 

flame. Since the spectrum is very simple, a visual 

examination by means of a hand spectroscope is 

sufficient. Preliminary experiments with pure- salts 

of known elements should be helpful in learning to 

recognize the lines of these elements from their colors 

and positions. Yellow lines in such a flame are usually 

the well-known line of sodium, 5890 R ; red lines are: 

Li 6708 A, which is closer to the yellow Na line, and 

K 7668 A, situated further away. If the spectroscope 

has a scale, then one is able to record the scale 

divisions at which the lines appear, but even in a 

simple spectroscope without a scale, it is easy to 

estimate the positions of these lines. The blue line 

of indium, 4511 is very characteristic, but this° 

line is easily confused with Cs 4555 R; and Sr 4607 A; 

in this case it is difficultoto get along wpout the scale. 

The green lines Ti 5351 A and Ba 5536 A are more 

easily detectable. Rubidium gives a violet line 

4202 

An auxiliary prism fastened before the slit is 

very helpful. (The spectroscopes which are manufactured 

by the Optical-mechanics plant no. 5, are equipped 

with such prisms.) By placing a second burner at 

the side, two spectrums may be obtained simultaneously, 

one above the other. By putting the unknown sample 

in the flame of one burner, and a known salt or a 

mixture of salts into the other burner, one can determine 

without error what elements are contained in the sample. 

The following procedure is recommended for the gasoline 

burner: The powder of the unknown sample is placed 

in a crucible containing hydrochloric acid and metallic 

•zinc. The crucible is then placed next to the cup which 

serves to kindle the burner. Spray from the solution 

resulting from the generation of hydrogen will be 

drawn into the flame of the burner, and clear spectral 

lines can be observed. 

The data of spectroscopic analysis were in 

many cases useful in the determination of minerals. 

Compared with chemical analysis, spectroscopic 

analysis is cheaper and quicker. At the present time, 

spectroscopic analyses for tin in 2000 samples can be 

accomplished in 20 days at a cost of 5000 rubles; tin 

determinations by chemical methods would require 

10 months' work by two expert analytical chemists and cost 

50,000 rubles. Analyses for indium in 1000 samples, 

which were carried out in the spectral laboratory of the 

Lomonosov Institute, required a total of two months' work. 

It would take an expert chemist approximately 20 years 

to perform these analyses. 6/ 

8In recent years the X-ray spectroscope has also gained in popularity. 

Owing to its complicated make-up, however, it cannot be used in the field. 

See literature: Borovsky, I. B., Present status of the X-ray spectroscope 

abroad. Akad. Nauk, SSSR, Trudy Lomonosovsk. inst., 1937, tom 9, 

pp. 209-245 (standard literature); Borovsky, I. B. and Blokhin, M. A., X-ray 

spectral analysis, GONTI, 1939, pp. 1-493. 

23 

Bibliography 

Borovik, S. A. and Filippov, A. N., Spektral'nyy 

analiz. Sovremennye fiziko-khimicheskiye metody 

khimicheskogo analiza [Spectral analysis. Modern 

physicbchemical methods of chemical analysis1, 

Vyp. 1., Gcskhimtekhizdat, Leningrad, 1932. 

Gerlach, W. and W. , Spectrokhimicheskii emissionnyi 

analiz [Spectrochemical emission analysis] 

(translated from German under the direction of 

S. A. Borovik), ONTI-Khimteoret., Leningrad, 

1936. 

Ozerov, I. M. , Stannometricheskaya s"yemka 

kak poiskovyy metod [Stannometric survey as a 

prospecting method]: Razvedka nedr., 1937, 

No. 24, pp . 52-56. 

Tolmachev, Yu. M., Primeneniye spektral'nogo 

analiza pri geologopoiskovykh rabotakh [The 

application of spectrum analysis to geological 

prospecting operations]: Priroda, 1936, no. 1, 

pp. 28-31. 

Schheibe, Gunter, Khimicheskiy spectral'nyy analiz [ Chemical spectrum analysis] ONTI-Khimteoret., 

Leningrad, 1938. 

Strock, L. W. Spectrum analysis with the carbon arc 

cathode layer: 56 pp. London, 1936. 

Examples 

Exploration for tin: The Academy of Science 

is publishing "A practical guide for tin prospecting 

by means of the spectroscopic method. " B. L. 

Flerov (1938) describes the use of spectroscopic 

methods in prospecting as follows: 

"The spectrometallometric survey is being 

used more of late. Compared to panning, this 

method has these advantages: 1) it is useful in 

studying all types of mineral deposits; 2) it is more 

reliable, because the spectrograph makes possible 

the detection of powdered cassiterite, which is 

usually lost during panning, and of cassiterite-bearing rock; 3) the samples do not have to be carried 

far, and it is possible to work in the absence of 

water; 4) the tin content of the samples may be 

determined rapidly; 5) many analyses may be performed at low cost; and 6) samples may be taken 

from deep drill holes. 

"On the other hand, the spectrograph is 

several tens of times less sensitive than panning 

which easily exposes 20 mg of cassiterite in the pan 

(0.0002 percent). Parts of the sample are lost 

when using the spectrometer. Besides, panning 

requires only the most primitive devices, whereas 

spectrometry requires an electric current and a 

spectrograph. The chief disadvantage of a stannometric survey using the panning method is that it 

cannot be applied to sulfide mineral deposits having 

micro-occurrences of cassiterite; however, there 

are many sulfide deposits containing grains larger 

than 0.05 mm, which can be captured with a pan. " 

The author (B. L. Flerov) warns against 

excessive enthusiasm for the spectrograph, whose 

application may be limited to: sulfide and other 

deposits with micro-occurrences of tin; mineral 

deposits with layer of detritus too deep for easy 

drilling; large surveys which are economical of 
electric power and involve a great number. of samples 

of deluvium and ore which can be given a preliminary 

analysis on the spot; areas where water is absent. 

Small survey parties working on mineral deposits 

containing cassiterite coarsor than 0.2-0.5 mm may 

make a stannometric survey by planning. 

Comment (A. Fersman) 

Spectroscopic methods may also be applied to 

the qualitative determination of minerals which contain 

rare earths. Some rare earths give absorption lines 

when the mineral is examined in bright sunlight through 

a small hand spectroscope `(direct-vision). These 

absorption lines are very well displayed by apatite and 

monazite and permit one to distinguish apatite from 

beryl and monazite from garnet. 

FLUORESCENT METHODS 

By A. F. Sosedko with a supplement 

by A. Ye. Fersman 

Lately, the fluorescence of minerals under the 

action of cathode, ultraviolet, and other short waves 

has been successfully used in prospecting. At present 

there are over 400 known varieties of fluorescent 

minerals which have different colors of fluorescence, 

and which fluoresce to different degrees depending on 

the deposits from which they were obtained. Fluorescence is probably the effect of a disturbance in 

the equilibrium of the crystal lattice caused by mechanical rupture, or by the presence of extraneous 

atoms or ions in the lattice spaces. Each local 

disturbance of the electrostatic equilibrium facilitates 

the temporary transition of the lattice to a higher 

energy level, which on falling causes the emission 

of visible light. 

Unfortunately, there has been rio research into 

this problem and the principles for a classification of 

minerals according to their fluorescence is not at 

hand. Scheelite, which is difficult to distinguish from 

quartz, usually gives a very intense fluorescence of 

a lovely light blue color. However, there are varieties 

(sometimes from the same deposit) which are distinguished by a green color, arid specimens of scheelite 

are found which do not react at all under cathode and 

ultraviolet rays. Similarly, some diamonds will not 

fluoresce, although many do. 

The fluorescence of a substance under ultraviolet 

or cathode rays is caused by changes which occur within the molecule, the atom, or the lattice when bombarded 

by the rays. To become fluorescent a substance often 

requires the presence of a small number of extraneous 

molecules or atoms. These extraneous substances or 

"activators" are either tied to the original lattice by 

means of valence bonds or are present in the form of 

neutral atoms that are uniformly spaced within the 

crystal lattice, deforming and depressing it. In 

certain cases the activators are atoms of heavy 

metals, such as the atoms of sodium [sicl in rock 

salt. Observations on artificially prepared fluorescent 

compounds have shown that fluorescence is produced 

by a very small quantity of an activator, and that 

fluorescence reaches a maximum for a definite optimum 

quantity. In zinc sulphide the optimum concentration 

of the activator, copper, is 1 in 10,000. In some 

cases fluorescence is produced by such a negligible 

amount of activator that the activator cannot be 

detected. Different activators occurring in the same 

substance act upon one another to change the color of 

fluorescence or to extinguish it. The fluorescence 

produced by copper is extinguished by bismuth. 

Spectroscopic analysis shows that a different type 

of fluorescence is obtained where rare earth, chromium and nickel salts are present. Here the fluorescent radiation is apparently produced by rare 

earth, chromium or nickel ions which have been 

isomorphically substituted in the crystal lattice. 

Line spectrum obtained during fluorescence is 

caused by the activator ions rather than the mineral 

itself. Of the rare earths, samarium gives a reddish 

hue; praseodymium, red and green; ytterbium, an 

excellent violet; and chromium, red. 

There are some substances which are able to 

fluoresce without the presence of activators because 

of their lattice structure. These substances include 

the salts of the uranyl group, UO2. 

The fluorescence of a number of minerals, 

such as the carbonates, may vary from deposit to, 

deposit. Conditions prevailing during depositions 

may determine the character of fluorescence by 

influencing the lattice structure of minerals. 

Ultraviolet rays, cathode rays, and X-rays may 

be used in examining minerals. 

Sources of ultraviolet rays are the mercuryquartz lamp and the spark discharger. The mercuryquartz lamp i rich in ultraviolet rays in the range 

4000 to 2300 A. The mercury-quartz lamp also 

emits visible light. All visible light, except the 

violet portion, should be eliminated by a quartz 

glass filter tinted with nickel salts. This filter 

is transparent to the visible violet rays an to the 

ultraviolet rays in the range 2900 to 4000 . 

There are a number of minerals that do not 

fluoresce under the mercury-vapor lamp, but do 

fluoresce under shorter ultraviolet rays. Shorter 

ultraviolet rays are produced by a spark discharge 

between aluminum or iron electrodes. A semiportable 

spark unit operating from a regular lighting circuit 

has been constructed. A portable unit is also obtainable. The semiportable unit uses a high voltage 

transformer. The spark electrodes are placed in 

a tube equipped with a handle. This enables one to 

use the tube like a searchlight, pointing it in the 

desired direction. The source of current for the 

portable unit is a magneto driven by a crank and 

gear system. The magneto weighs from 10 to 12 

kilograms and can be carried by one person. 

A filter is not used with a spark-discharge 

outfit because it stops the short ultraviolet rays as 

well as the visible rays. The fluorescent light must 

be observed either mixed with ordinary visible 

light, or by means of a quartz monochromator. 

Ultraviolet rays may be intensified to detect weakly 

fluorescent minerals by using a quartz condensing 

lens. The minerals are placed at the focal point. 

Many minerals fluoresce strongly under 

cathode rays when in a vacuum. Cathode tubes with 

either cold or hot cathodes may be used, although 

24 
tubes with cold cathodes are safer and require a 

vacuum of only 0.01-0.001 mm of mercury. 

A cathode tube with cold cathodes usually consists 

of a closed chamber containing an aluminum cathode 

in the form of a disk; the anode consists of any material. The anode serves as a support for the mineral 

to be examined. The vacuum in the tube is adjusted 

and power amounting to 5 to 15 kilowatts is applied. 

It takes from 1 to 2 minutes to prepare a sample for 

examination. Field equipment has also been constructed 

for cathode ray examinations. 

The successful use of ultraviolet rays to detect 

scheelite rapidly even in minute grains has established 

the use of ultraviolet rays in identifying a number of 

minerals. However, the accumulated evidence shows 

that a specific mineral may fluoresce different colors 

or, in some instances, not fluoresce at all. It is 

often impossible to determine the identity of the fluorescing mineral. These circumstances have caused considerable indifference to the use of fluorescent analysis 

in mineralogy, almost to the extent of its being entirely 

neglected. However, there is little doubt that despite 

certain limitations, fluorescent analysis is of great 

importance and is a necessary method not only for 

the determination of minerals, but for the practical 

operations of mining and concentrating scheelite. 

Fluorescent minerals may be examined under 

the microscope by exposure to ultraviolet rays as 

follows: The ultraviolet rays are produced by a spark 

discharged and then passed through a condensing lens 

into the monochromator. In the monochromator the 

ultraviolet rays are separated from the visible light. 

By means of a quartz tube, which takes the place of a 

mirror, the rays are passed into the microscope tube. 

The mineral to be examined is finely powdered and 

placed on a quartz slide upon the microscope table. 

The exposure of minerals to cathode rays is feasible 

if the cathode tube is of such dimensions that it can 

be placed upon the microscope table. The fluorescence 

in the vacuum is observed through the glass of the 

upper part of the tube. 

Study of the fluorescence of minerals when 

exposed to X-rays has not yet received widespread 

attention; we will omit a description of the X-ray 

apparatus. 

Up to now the fluorescence of minerals has not 

received a thorough systematic investigation; we have 

only a few separate unsystematic observations. 

The limited use of fluorescent analysis is due 

to our lack of knowledge of the causes of fluorescence. 

The type and intensity of fluorescence depend upon 

the presence of activator substances, which make up 

part of the traces of impurities in the mineral. 

Minerals are seldom chemically pure, for they usually 

contain a great variety of impurities. These impurities 

either enter the crystal lattice in the form of isomorphous 

substitutions or are distributed within the lattice as 

free atoms or molecules. By understanding the 

different types of mineral fluorescence, we are able 

to classify minerals in a new way. Impurities in a 

mineral are frequently determined by the environment 

of the mineral when it was formed. Assuming that 

minerals of similar origin contain similar impurities 

we can conclude that fluorescent analysis may be used 

25 

successfully in the study of mineral deposits, in 

bulk assaying of them, and in mineralogic study of 

geochemical provinces. Geochemical studies should 

be preceded by a study of the fluorescence of the 

minerals involved in these problems. When the 

fluorescent response of different minerals of a 

given deposit or given province has been determined, 

then fluorescent analysis may be effectively applied. 

The minerals in heavy concentrates may then be 

quantitatively determined, and many phases of ore 

analysis, such as heavy-mineral analysis, the 

analysis of mill tailings and the determination of 

losses in slimes will be speeded up. It may also 

be used for determining the genesis of minerals, 

and establishing the part they play in the genesis of 

ore deposits. 

Not all minerals possess the property of fluorescence; metallic and dark-colored minerals do 

not fluoresce. According to P. P. Pilipenko, fluorescent minerals possess ions crystalline lattices. 

Furthermore, not all fluorescent minerals 

fluoresce when exposed to different sources of 

radiation. A comparatively small number fluoresce 

under the action of long ultraviolet waves. They 

fluoresce somewhat more and generally with far 

greater intensity under the action of ultraviolet 

rays from the spark discharger. However, examples 

are known where minerals radiate under the rays of 

the mercury lamp, but do not radiate under the rays 

of the spark discharger. 

A greater number of minerals fluoresce under 

cathode rays than under ultraviolet rays. A few 

investigators claim that minerals radiate more 

intensely under cathode rays, but their research 

shows that minerals radiate a greater range of 

colors under ultraviolet rays than under cathode 

rays. Thus, calcite gives light yellow, pink, dark 

red, and dark purple under ultraviolet rays, whereas 

under cathode rays it radiates only yellow to fiery 

yellow colors. Because of this, it is hard to tell 

which light source is the most suitable. It is important to select the most efficient light source for 

each mineral. 

In studying the fluorescence of minerals it is 

sometimes necessary to create conditions which 

will increase the intensity of the fluorescence of 

the specimen to be examined. In examining minerals under cathode rays it is recommended that a 

fresh fracture be used. Crushing the mineral to 

a powder enlarges the surface of exposure and increases the fluorescence. Scratching the mineral 

with a needle or a knife will increase the intensity 

of the fluorescence. When using X-rays, however, 

powdering the mineral will cause the fluorescence 

to disappear, and the examination should be made 

with a large fragment of the mineral. 

Some colored minerals will fluoresce only if 

they are ground into a fine powder and examined 

under a microscope. Sapphire is an example. 

Certain minerals like wolframite and molybdenite can be changed into fluorescent compounds by 

means of a chemical process. This is used when 

prospecting for them in heavy-mineral studies. 
With fluorescent analysis a quantitative as well 

as a qualitative determination of fluorescent minerals 

can be made. Samples are crushed and separated 

into fractions according to their grain sizes. The 

grains are then counted under a microscope. A number of methods of making the quantitative calculation 

have been proposed which we need not discuss. The 

accuracy of the calculation is sufficient for technical needs. This method gives the following sensitivities for the determination of scheelite: 

Diamond. --Fluoresces with a light blue or 

yellow green color. 

Apatite. --Specimens from different deposits 

fluoresce different colors, such as pink, violet, 

green, or yellow. 

Zircon. --Fluoresces an intense orange which 

is easily distinguished from the fluorescence of other 

minerals. 

Percent Percent Data upon the fluorescence of a number of 

concentration sensitivity other minerals is given in Table 14. 

1.8 1 

5-10 2 

10-20 3 

The' quantitative determination of fluorescent 

minerals is being currently applied to scheelite, zinc, 

and corundum ores. It is especially applicable to 

scheelite and zircon for which a method has been 

worked out in detail. Its advantages are rapidity 

(10-12 minutes for 6 determinations) and a cost many 

times lower than the average cost of a chemical 

analysis. 

The fluorescent response of characteristic 

minerals is described below. Scheelite, the carbonates, and fluorite give the most intense fluorescence: 

Scheelite (CaWO4). --Scheelite fluoresces very 

well, u always under the rays of the mercuryquartz lamp. It fluoresces an intense blue (sometimes green), making it easy to distinguish from the 

other minerals. Fluorescent analysis is very applicable in prospecting for scheelite, in guiding survey 

operations, or as a control in the operation of scheelite 

concentrating equipment. 

Carbonates. --Among the stable minerals, calcite 

and aragonite are especially characteristic because 

of their sensitivity and variety of colors. With respect 

to ultraviolet and cathode rays there are two types of 

calcite. One does not fluoresce when irradiated; the 

other does. Under ultraviolet rays calcite fluoresces 

waxy-yellow, pink, or dark red. Under cathode rays 

the fluorescence is less varied, being yellow and 

fiery-yellow. P. P. Pilipenko attributes the different colors of calcite's fluorescence to impurities, 

mainly of manganese and partly of iron. 

Fluorite. --Fluoresces intense blue or bluish 

colors. 

Cryolite. --Does not fluoresce under the ultraviolet ray the mercury lamp, but under the rays 

of the spark discharger it gives a weak fluorescence 

and possesses a clear white phosphorescence. This 

property is important in prospecting for cryolite in 

the Il'men mountains and on the Kol'skiy Poluostrov 

[Kola peninsulal. 

Corundum. --Different types of corundum 

fluoresce differently. The red corundum from Yakutsk 

fluoresces an intense ruby color which is due to inclusions of chorium. Massive sapphires from Semizbugu and from central Asia usually do not fluoresce, 

but when powdered and examined under the microscope 

they fluoresce light blue. 

26 

Conclusion: 

Fluorescent analysis frequently makes possible 

rapid mineral identification and quantitative estimation of the mineral composition of a sample. 

The application of fluorescent analysis is complicated by the fact that the same minerals from 

different deposits may fluoresce differently, and that 

different minerals may give identical fluorescence. 

The type of fluorescence is chiefly determined 

by tiny amounts of impurities. Thus, minerals 

formed under the same conditions will contain nearly 

the same amounts of impurities; and minerals from the 

same deposit or the same geochemical province will 

have the same fluorescent properties. In this case 

fluorescent analysis is extremely valuable in bulk 

sampling or concentrating. 

Fluorescent analysis may be successfully applied 

in the field. 

Though the method of fluorescent analysis is 

still not perfected, it promises to give valuable and 

productive results. It should be tested out in every 

field of mineralogy with the aim of expanding and 

extending it. 

Bibliography 

Bogoslovskiy, M. G., Savitskaya, P. V. and Solomkin, 

S. G., Lyuministsiruyushchiye mineraly [Fluorescent minerals1: Soy. geologiya, 1938, no. 10, 

pp. 99-110. 

Komovskiy, G. and Abolenskiy, F. Lyuministsentsiya 

mineralov i apparatura dlya yeye issledovaniya 

[The fluorescence of minerals and apparatus for 

its investigation]: Probl. soy. geologiya, 1938, 

no. 4, pp. 332-338. 

Komovskiy, G. and Razumnaya, E. G., Mikroskop s 

katodnoy yacheykoy i lyuministsentnyy kolichestvennyy 

analiz [A microscope using cathode rays for qualitative fluorescent analysis]: Sov. geologiya,1938, 

no. 11, pp. 111-117. 

Savitskaya, P. V., Lyuministsentnyy analiz shlikhov 

[Fluorescent analysis of heavy minerals]: Sov. 

geologiya, 1938, no. 6, p. 123. (The chemical preparation of heavy minerals to determine fluorescent 

wolframite and molybdenite). 

Flint, E. and Bogoslovskiy, M., Metody katodnoy 

lyuministsentsii [ The method of cathode fluorescence]: 

Trudy Vses. inst. min. syr'ya, 1937. (Especially 

for the analysis of heavy minerals). 

De'riblerle, M., Les applications practiques de la 

luminiscence The practical application of fluoresence), 275 pp., Paris, 1938. 
Table 14. --Fluorescence of minerals in cathode and ultraviolet rays 

Mineral In cathode rays In ultraviolet rays 

azure, dark blue, green. 

In the Urals: bluish. 

yellow, pale green, orange, lilac. 

violet, yellow, pink. 

violet. 

violet, cherry. 

violet. 

light green. 

dark blue. 

light blue, light green, light violet. 

orange-red, light blue. 

pale pink, orange. 

red. 

greenish. 

light green. 

light blue, dark blue. 

raspberry. 

light yellow. 

pink. 

light blue. 

blue, light blue. 

azure, violet, yellow-green. 

pink, Violet, red. 

violet, yellow, pink. 

violet. 

orange. 

greenish-yellow. 

light yellow. 

dark red. 

violet. 

yellow. 

yellow. 

greenish-blue. 

Diamond 

Apatite 

Barite 

Beryl 

Bauxite 

Gypsum 

Diaspore 

Dumortierite 

Calamine 

Corundum 

Lovchorrite 

Lepidolite 

Molybdenite 

Oligioclase 

Orthoclase 

Powellite 

Petalite 

Smithsonite 

Sphene 

Topaz 

SPECIAL METHODS 

We will deal here with some special methods of 

prospecting based on phenomena accompanying the 

oxidation of sulfide ores, such as the secondary migration of solutions and the rH and pH of the environment. 

Prospecting Based Upon the Study of 

Oxidation Processes. 

Oxidizing sulfide ore bodies have some important 

diagnostic features (discussed in Chapter V,. page 317). 

These features are of such definite character and 

magnitude that several special geochemical and geophysical methods have been developed for their study. 

S. S. Smirnov (1936, especially pp. 123-127), 

a specialist on oxidation processes, has followed the 

American practice of analyzing the structure of secondary minerals, especially limonite, occurring as 

pseudomorphs in different sulfide minerals. A detailed study of the structure of secondary minerals 

(shape, size, and type of crystal system; porosity, 

texture, type, and color of limonite) will reveal the 

identity of the primary mineral (especially, pyrite, 

chalcopyrite, pyrrhotite). This method may be applied 

especially to prospecting for copper, and sometimes 

zinc and lead ores. 

Anyone who is interested in gossans is referred 

to the original treatises. 

Prospecting by Thermal Effects 

Oxidizing sulfide minerals give off heat. N. I. 

Sofronov has suggested that a study should be made 

of the thermal properties of oxidizing mineral deposits, 

but there have not yet been experimental applications 

in prospecting. 

27 
Prospecting by the Chemistry of 

Secondary Processes 

The low pH of water in oxidation zones and gossans 

provides a good prospecting indicator. Another important indicator is a high sulfate ion concentration in 

the waters. The dispersion halo of the sulfate ion is 

sometimes quite large and allows one to map areas 

containing primary sulfides (see page 169). 

Prospecting for Salt Deposits on the 

Basis of Seco-ria-ary Migration 

Study of borate depoSits in'western Kazkhstan 

has led to conclusions important in reconnaissance 

prospecting work (Nikolayev, 1938). Accumulations 

of "primary" boron salts are chiefly associated with 

the final products of crystallization--the potassium 

salts. During continued weathering the potassium 

salts are readily washed out, whereas the boron salts 

are altered, especially in the presence of calcium 

and magnesium salts, to less soluble compounds. The 

R203: RO ratio drops from 1.67 to 1.5 to 1.25 and 

lower (R represents Ca and Mg). 

Prospecting for sedimentary borate should be 

guided by textures indicating leached potassium minerals. After the borates have been located, potash 

deposits should be sought at depth or in places protected from water. These results deserve attention and 

are an excellent example of the application of a thorough 

analysis of geochemical features to prospecting. 

The Use of Redox, or rH 

(oilTatToTi- r ed uc ti on potential) 

Proximity to seepages of petroleum and volatile 

hydrocarbons may be accurately expressed in terms 

of changes in rH. Reducing conditions which may be 

measured accurately increase inversely as the distance 

from the seepage source. Such investigations have 

been carried out by the Fuels Institute of the Academy 

of Sciences along a line of Caucasian mud volcanoes 

(Gubkin and Fedorov): 

"Being closely acquainted with oxidation-reduction conditions in the crater of the ,mud volcano, we 

became interested in the problem of why the rH of 

the mud breccia (?) at different depths changes in 

proportion to its distance from the nucleus of the volcano. 

"A thorough consideration of the acquired data 

enables us to deduce the existence of a definite rule 

here, which may be described in the following manner: 

Samples of liquid breccia taken from the crater of a 

mud volcano; in which either in the immediate vicinity 

or close to it (at distances of not more than one kilometer) there is an indication of petroleum, as a rule 

show a decrease of rH with depth, or in other words 

an increase in reduction intensity (9 cases out of 11). 

In a zone of the same radius around volcanoes, which 

contains no petroleum, 7/ this rule was not observed 

(6 cases out of 8. 8/) 

7Asphalt may be present. 

&The first two exceptions seemed to be due to accidental errors. 

The last two exceptions are probably not due to accidental errors: It is 

probable that these volcanoes actually belong in the first category. 

28 

"As a result of our determinations of rH in the 

primary rocks along a line of approach to the volcano 

we noticed a variation in rH value depending on 

whether the area is related to oil deposits of commercial significance, or for small volcanoes not in the 

immediate vicinity of zones of high oil content. In 

the first case, we find that the reduction potential in 

primary rocks was proportional to the nearness of 

the center of the volcano. This was not only true 

for rocks of the same formation, but for rocks taken 

from different formations. In the second case, this 

tendency was observed only along the trend of a 

single thin stratigraphic unit, or was not observed at 

all. These correlations were clearly shown at several places investigated by us (Lok-batan, on the one 

hand; and the Tyul'ki-tapa and Bulganakskiy volcanoes 

on the other). For a number of reasons for which we 

were not responsible, we were unable to check the 

correlations on the large scale necessary for final 

proof. " 

"Thus, these investigations are only of a preliminary nature. " 

Nevertheless, this method deserves considerable attention. Oxidation-reduction potential will 

undoubtedly become an important indicator in prospecting for mineral deposits where reduction processes 

are involved (petroleum, natural gas, asphalt, and 

to some degree, coal). However, a direct determination of redox intensity is only possible in the liquid 

and gaseous phases, and is much more difficult in the 

study of solid substances. 

In addition to direct determinations of rH, indirect•conclusions as to its approximate value may 

be made on the basis of studies of stratigraphic sections and their facies changes. For example, a 

study of the relationships and distribution of ferrous 

and ferric oxides in marine sediments may lead to 

conclusions regarding the rH pattern in the marine 

basin and even to a method of prospecting. A lowering 

of rH inhibits the deposition of MnO2 and leads to the 

formation of silicate iron ores (chamosite and 

thuringite). See the work of V. V. Shcherbina (1939) 

on the paragenesis of sulphur compounds. 

The Use of pH Determinations 

Determinations of pH have not been applied 

widely to prospecting because of some inherent difficulties. The determination of pH in waters indicates 

only the acidity and alkalinity produced by recent 

geological processes, such as the formation of gossans 

and weathering. In studies of ancient weathering, 

data on modern weathering must be used very carefully. Nevertheless, the determination of pH in 

studies of contemporary processes furnishes some 

important information: at low pH (3 to 5) we should 

expect the precipitation of aluminum silicates as clays; 

in ore deposits, we should expect the precipitation of 

the ochers of heavy metals (W, Mo), the formation of 

free sulfuric acid with the evolution of CO2 gas on one 

hand, and the coagulation of Si02into opals and semiopals on the other. It is unfortunate that these problems have not been thoroughly studied by geochemists 

as yet. Only the interesting work of Khitarov (1938) 

shows the important role of pH in the migration of 

metals, such as molybdenum in a supergene environment. Low pH results from two important processes: 
the oxidation of natural sulfur deposits and the 

oxidation of sulfide deposits. 9/ 

The migration of the elements is different in 

regions with high pH (9-14). In these regions SiO2 

is carried off in solution, while Fe2O3, Mn02, and 

sometimes A1203 (at a lower pH) are precipitated. 

In complex ores, Mo and W are taken up by alkaline 

solutions. In bituminous deposits, parts of the organic 

material is extracted (Fersman, 1937, pp. 424-426). 

Studies of pH of acid and alkaline solutions 

permit us to estimate the pH of various geological 

processes on the basis of paleogeographic and geological criteria. For example we know that pH is a 

function of the depth zones in marine waters, thus: 

Variation in pH with depth for the South Atlantic Ocean below the tropics 

[According to A. V. Kazakov (1938)] 

Zone Depth in 

meters 

Temperature in 

degrees C. 

pH 

1 0-50 20 8.15 

2 50-500 20-7 8.1-7.7 

3 500-1500 7-4 7.7-8.0 

4 over 1500 4 8.0 

5 sea floor about 0.5 7.95 

Palegeographic data can tell us in which zone 

a sediment should be classified; a study of the sedimentary basin may determine the probable pH at which 

a given rock was formed, and a number of conclusions 

may be drawn about the accumulation of different minerals. Applying geochemical principles, we may expect 

the accumulation of phosphorite in zone 2 at the lowest 

pH, nearly neutral (7. 7). 

Botanical Methods 

It has long been known that the character of 

vegetative cover may serve as a prospecting guide. 

In 1938 S. M. Tkalich pointed out the value of vegetation as an aid in prospecting. Referring to an extensive literature, he listed a special variety of violet, 

growing on zinc-rich soils (calamine violet), the 

peculiar growth of certain grasses in areas rich in 

lead, and the well-known research of Franz Unger in 

1836 upon difference in the vegetative cover of siliceous and calcareous soils. These specific peculiarities 

of the vegetative cover were much emphasized by 

studies of the mineralogy of the island of Elba in 

1909, because there it was entirelT clear that the 

vegetation growing over the serpentines was very 

different than that over the granites which cut through 

the serpentines. One does not need to be a botanist 

to recognize these sharp distinctions. 

The idea of using plants as indicators has been 

repeatedly stressed by investigators in coal districts. 

Yu. A. Zhemchuzhnikov in a number of cases noted 

specific types of vegetation cover in regions of outcropping coal deposits. Engineer Ivashkevich, while 

mapping the Sakhalin coal deposits noticed that areas 

underlain by Cretaceous rocks were covered by 

Siberian coniferous forest, whereas the foothills and 

aSee the work of Sedletsky regarding this problem. For the relation 

of clays to pH see Deribere (1938). 

valleys underlain by Tertiary coal deposits were 

covered by a forest of birch, alder and spruce. 

A great deal of attention has been paid to the 

vegetation at the apatite deposits in the tundras of 

Khibinsk. In valleys where the apatite rocks have 

undergone weathering, the vegetation is thicker than 

in valleys where there has been no weathering and 

concentration of phosphorus. There is also a difference between the lichens growing on bare nephelite 

rock and on apatite rocks; however, this difference 

was more of a quantitative than qualitative nature. 

In his paper, S. M. Tkalich points out that from 

the prospector's point of view, plant indicators may 

be divided into two groups. One group serves as 

direct indicators, indicating the presence of different 

substances. For example, saltwort indicates the 

enrichment of sodium chloride in the soil; Viola 

zincifera indicates zinc; peat moss indicates peat 

deposits. 

Undoubtedly, biogeochemical methods will 

yield valuable information about areas containing 

large quantities of a certain element. Plants rooted 

in the dispersion halo of a mineral deposit will absorb 

the corresponding element in increased amounts that 

can be determined in the plant ash. 

Tkalich lists the following four rules with regard 

to this problem: , 

If no strict proportion exists between the concentration of a salt in the soil solution and its concentration in the plants, the salt will be enriched in the 

plants. 

Two identical plants, one growing outside a 

dispersion halo and the other growing within, will 

contain different concentrations to the same salt 

even though all other conditions be the same. 

29 
The amount of any element in the ash of a plant 

may be selective and it is necessary to compare the 

concentration of this element with that in similar 

plants from other localities. 

The best parts of the plant to use for ash analysis 

are the plant organs, especially the leaves. 

Fifteen years ago S. P. Aleksandrov expressed 

similar ideas as the result of his studies of radium 

deposits in south Fergana. He analyzed the ashes of 

plants growing in the vicinity of a mine and found 

greater concentrations of vanadium and uranium 

than he did in plants growing in similar soils in other 

areas of South Fergana. More recently, analagous 

methods have been used in Sweden by Brundin and 

Palmquist, who determined gold, tungsten, molybdenum, 

tin and other metals in the ashes of leaves. Apparently, 

their experiments have yielded positive results in the 

forests of northern Sweden. 

These ideas were checked systematically by 

S. M. Tkalich in the area of the Unashinsk arsenopyrite 

deposits in the Far East. He used the following 

method: 

Several traverses were run across the ore body 

at distances of 30 to 35 meters from one another. 

Leaves were collected from plants at regular intervals, 

with closer spacing in the area of the ore body. The 

concentration of the element being sought was determined in the ashes of the leaves. In this case the 

element was iron. The points from which the samples 

had been taken were marked on a map. Because of 

the nature of the analysis the average concentrations 

of the metal compounds were expressed in semiquantitative terms: absent, trace,-present, abundant. 

Points containing similar amounts were contoured, 

and an interpretation was made concerning the center 

of dispersion of the known chemical element. 

In this case three traverse were laid out, and 

leaves of beach grass (Calamagrostis) were collected. 

The ashes of the plants were analyzed for ferric oxide 

and ferrous oxide. A diagram was obtained which 

showed a high iron content in ashes of plants growing 

near the adit on the lower vein, and also near the 

lower adit on the principal vein. In areas away from 

the deposit, the iron content was less. 

Although attempts to verify the assumptions 

behind this method have not given very clear results, 

the method itself is noteworthy. 

Plants, according to the data of V. I. Vernadskiy 

and A. P. Vinogradov, very clearly respond to changes 

in environment. A plant cell behaves as a very accurate 

indicator, revealing the abundance or deficiency of the 

different chemical elements; the brilliant research of 

A. P. Vinogradov in establishing the different biogeochemical provinces has proved that botanical 

studies may be applied to the solution of many practical problems. Therefore, we must emphasize the 

importance of biogeochemical research in prospecting, and recommend further research under natural 

conditions near mineral deposits. 

Bibliography 

Deribdrd, M. , 1938, Application geologiqu4 de 

pH [Geologic application of the pH]: Soc. geol. 

France Compte rendu, fasc. 1-2, p. 17. 

Fersman, A. Ye., 1937, 0 velichine pH v raznykh 

geokhimicheskikh sistemakh [The pH of different 

geochemical systems]: Geokhimiya, v. 3., pp. 

424-426. 

Gubkin, I. M., and Fedorov, S. F., 1938, Gryazevyye 

vulkany Sovetskogo Soyuza [The mud volcanoes of 

the Soviet Union], Akad. Nauk SSSR, Inst. goryuch. 

iskop., pp. 33-34. 

Nikolayev, A. V., 1938, Fiziko-khimicheskoye 

izucheniye boratov [Physicochemical studies of 

borates], Doklady zapiska. 

Shcherbina, V. V., 1939, Okislitel'no-vosstanov. 

potentsial v primenenii k izucheniyu paragenezisa 

mineralov [Oxidation-reduction potential as applied 

to the study of the paragenesis of minerals]: Akad. 

Nauk SSSR Doklady, tom 12, no. 8, pp. 508-510, 

Smirnov, S. S., 1936, Zona okisleniya sul'fidnykh 

mestorozhdeniy [ The oxidation zones of sulfide 

deposits1, ONTI. 

Tkalich, S. M., 1938, Opyty issledovaniya rasteniy 

v kachestve indikatorov pri geologicheskikh poiskakh 

i razvedkakh [Experimental investigation of plants 

as qualitative indicators of geological prospecting]: 

Akad. Nauk SSSR, Vestn. Dal'nevost. Filiala, 

no. 32, pp. 3-25. 

Uspenskiy, Ye., 1925, Zhelezno, kak faktor 

raspredeleniya vodorosley [Iron as a factor in the 

distribution of algae], Trudy Botanich. inst., 

Moscow. 

VISUAL AERIAL-SURVEY METHODS 

The color of rocks and their resistance to 

weathering stand out in an aerial survey 10/. As 

shown in Chapter II, both of these features are related to the structure of crystals. The resistance 

of minerals and rocks to weathering is due to the 

ability of the crystal lattice to withstand destruction 

by mechanical, chemical and physiochemical weathering and erosion processes. Petroleum-bearing 

horizons in Turkmenistan, and also in California, 

were mapped using the color of rock in sequences 

containing petroleum. Ores, and especially quartz 

veins, are very easily mapped by visual studies of 

aerial photos. Quartz veins are often characterized 

by their topographic relief and by their extensions 

over large distances, so that tectonic breaks and 

even faults may be recognized, especially in regions 

without vegetation. Ore depOsits rich in sulfides 

stand out by their brown and rust colors, which are 

easily identified. Outcrops of sulfur, alum, and 

alunite are distinguished by their white outcrops. 

In Canada large veins of ore containing high 

concentrations of hematite and red dolomite were 

determined from the air. This led to the discovery 

of a new vein of pitchblende near Great Bear Lake. 

"'Caveman, A. V. Aeros'yemka i issledovanie priroiclnykh resuraov 

[Aerial survey and the investigation of natural resources) , Akad. Nauk 

SSSR Izd., 1937, 185-233. 

30 
The areas most favorable for prospecting by 

aerial surveys are the mountain regions about, the 

timberline and.the bare tundra. 

GEOPHYSICAL METHODS OF PROSPECTING 

It is not my purpose to give a detailed description of geophysical prospecting methods (Sel'skiy, 

1938), which have been so widely applied in recent 

years for mineral prospecting, as a great number of 

investigations have already been made and practical 

manuals are obtainable. Each year brings more 

success in their development, and the sphere of 

their application is constantly widening, making it 

possible to map the geology under a thick blanket of 

alluvium, conglomerate, soil, tundra, sand, or 

forest. 

However, I would like to point out that although 

-these methods are called "geophysical, " actually 

they are geochemical methods, since they are based 

on geochemical, the crystallochemical, and mineralogical properties of ores and their constituents. 

Therefore, the future progress of the geophysical 

methods depends not only on technical development 

and improvements in equipment, but also on detailed 

studies of different ore bodies. 

With the exception of the radioactive method 

which we will describe later, there are five types of 

geophysical methods: geothermal, seismic, gravitational, electrical, and magnetic. 

The geothermal method is based upon the 

thermal conductivities of rocks and minerals, and 

upon the analysis of those processes of the earth's 

crust which are accompanied by transfer of heat. 

(See page 215). 

The application of this method demands a 

thorough knowledge of the thermal conductivities pf 

individual minerals and rocks, as well as a geochemical study of thermal processes which accompany 

different natural reactions. So far there has been 

insufficient experimental research in this field, and 

therefore geothermal methods have not been widely 

used (Kraskovskiy, 1938). 

During the past few years seismic prospecting 

methods have been greatly developed, and there is no 

doubt that with further improvement, they will yield 

even more valuable results (Gamburtsen, 1938). 

These methods are based on stresses produced in 

rocks by elastic waves. An analysis of these waves 

yields a general picture of the rock type and structure. 

Let us note that in granites and crystalline ,schists 

the waves are propagated with a velocity of 4.5 to 6.5 

kilometers per second; somewhat lower in limestone 

(3.5 and 5.5 kilometers per second), [and] lower 

still in sandstones (1. 5-3 kilometers per second). 

There is little doubt that the future success of 

seismic methods depends on an accurate knowledge 

of the elastic moduli of minerals and rocks (Koridalin, 

1938; 1939); these have been studied very little. 

The mechanical properties of crystalline substances 

have been neglected in the study of physics of crystals 

in recent years, even though the future success of 

seismic methods will depend on the theory of the 

elastic properties of minerals and rocks. 

31 

Gravimetric methods are much more accurate 

and practical. They are based upon density contrasts, which is of significance in prospecting. 

Gravimetric methods have a high-instrumental accuracy over a wide range, enabling us to solve a 

number of geologic and geochemical problems. 

The gravitational method permits us to draw 

definite boundaries between such rocks as gneisses 

with a specific gravity of 2.6-2.7 and limestones 

with a specific gravity of 2.8-2.9. This difference 

of 0.1-0.2 in specific gravity is based upon the 

chemical composition of the rocks and marks the 

boundary between two chemical systems. 

It is important to apply the gravimetric method 

wherever a distinct difference in specific gravities 

exists. This gravity contrast is characteristic of 

salt deposits and of iron ores. It is possible that 

gravimetric methods could be applied successfully 

in prospecting for chromite deposits. 

The specific gravities of minerals and rocks 

have been determined accurately enough to form a 

basis for the gravitational methods. Of course, the 

difficulty is that rocks consist of minerals having 

various specific gravities, which often equalize the 

sharp contrasts between different rocks and do not 

permit the determination of results by the gravimetric 

method. 

Magnetic methods are one of the most important 

geophysical methods. They are based upon the ferromagnetic and diamagnetic properties of mineral 

deposits. 

The extensive application of magnetic methods 

is due to the accuracy of the instruments and the 

sharp differences between the magnetic properties 

of minerals. 

A magnetic survey gives clear results even for 

very small anomalies (100-200 gammas) whereas the 

magnetic contrast, measured in the same units, for 

minerals is much greater, and may be expressed in 

the following manner: magnetic iron 150 thousand 

gammas, dia.base 15 thousand gammas, limonite 

from 100-500 gammas, alluvial gold up to 300, 

granites 150-300, and salt 30-40 gammas. 

Magnetic methods would be even more successful if magnetic anomalies and the magnetic properties 

of minerals and rocks were studied in greater detail. 

Magnetic and ferromagnetic properties are possessed 

by a special group of chemical elements, located in 

the middle of the periodic table, and are basically 

related to the discharging and charging of the electronic shells. The compounds of iron have definite 

paramagnetic and ferromagnetic properties. This 

is also true of nickel, cobalt and manganese, to a 

lesser degree chromium, and the platinum minerals. 

The study of the magnetic pprmeability of minerals 

involves problems of a crystallochemical and geochemical character. Magnetic properties of minerals depend not only on the metals present, but 

also on the character of the crystal lattice and on the 

distribution of the metal within it. An increase in 

magnetism is due to the presence in the crystal 

lattice of ions of the same element in different 

valence states. 
The magnetic properties of iron are an excellent example of this. Magnetite consists of a 

complicated interweaving of ions of ferrous and 

ferric iron, while in metallic iron we have an unstable interchangeable valence state resulting in 

zero. Similarly, with cobalt, chromium and manganese, the presence of ions with different numbers 

of completed electron shells always results in increased paramagnetism. Compounds which contain 

unstable ions with changeable valences and which 

are characterized by the presence of free electrons, 

I have named "berzelides. " The investigation of 

this type of compound is important because paramagnetism in these compounds is accompanied by 

the absorption of light rays of dark blue or green 

colors. 

The development of magnetic methods demands 

a study of the magnetic properties of the natural 

crystal lattices and the relation of these properties 

to the conditions to their formation. 

New and more accurate data will enable us to 

perfect magnetic methods of prospecting for magnetite, 

for hematite, and for subsurface alluvial deposits of 

gold and platinum containing magnetic sediments. 

Magnetic methods may be applicable in the exploration and study of mineral deposits of bauxite which 

are associated with ferrous hydrates. Similarly, 

they could be used in prospecting for manganese ores, 

which have unstable valences. 

A second problem is the study of the magnetic 

properties of sulfide ores, and in particular, pyrrhotite and some copper ores. 

A third problem deals with the investigation 

of salt deposits, which give negative anomalies due 

to the diamagnetism of rock salt. 

Recently, electrical methods have achieved 

considerable success and wide application. They 

involve the study of the electric and electromagnetic 

fields resulting from both natural and artificial 

electric currents in the earth's crust. 

Many different methods may, be used in 

electrical prospecting to establish and measure the 

electromagnetic fields. We recommend study of the 

conductance and the electromagnetic properties of 

crystalline substances which have been studied less 

than the magnetic properties. Electrical methods 

have not yet been supported by quantitative study of 

the electrical properties of minerals, especially 

sulfides, for which these methods are of special 

interest. The conductivity of the sulfides is closely 

related to their crystal lattices (which are of the 

atomic rather than the ionic type), and to the distribution within the lattice of individual atoms of 

metal and sulfur. 

In addition to artificially created electromagnetic fields, there are natural electric currents 

created by natural chemical reactions, such as the 

oxidation of sulfides, or contact of bodies of different chemical compositions. All of this indicates 

that further research and study should be done. 

Bibliography 

Gamburtsev, G. A., 1938, Seysmicheskiye metody 

razvedki [ Seismic methods of explorationl, ONTI. 

Koridalin, Ye. A., 1938, Kora vyvetrivaniya [ Zone 

of weathering]: Trudy Seysmol. inst., no. 79. 

1939, Izucheniye stroyeniya zemnoy kory 

seysmicheskimi metodami [A study of the earth's 

crust by seismic methods] Akad. Nauk SSSR Izd., 

pp. 46-73. 

Kraskovskiy, S. M., 1938, Obzor glavneyshikh 

rezul'tatov geotermicheskikh izmereniy [A summary 

of the most important results of geothermal 

measurements]: Izv. Geog. obshch., •no. 4-5, 

pp. 612-628. 

Sel'skiy, V. A., 1938, Razvitiye prikladnoy 

geofiziki [The development of applied geophysics]: 

Trudy Seysmol. inst., no. 79 (9). 

RADIOACTIVE METHODS OF PROSPECTING 

By G. V. Gorshkov 

Introduction 

The radioactive method is based on the difference between the measurable radioactivity of 

mineral deposits and that of surrounding rocks. 

The difference may be positive (the radioactivity 

of the mineral deposit is higher than that of the 

surrounding rocks), or negative (the radioactivity 

of the ore mineral is lower than that of the surrounding rocks). Deposits with radioactivities higher 

than in surrounding rocks are easier to detect than 

those with lower radioactivities. 

If a mineral deposit has a higher or lower 

radioactivity than surrounding rocks (sedimentary 

or igneous), it will produce a radioactivity anomaly 

providing that the other physical properties (ability 

to emanate, density, porosity, and others) of the 

rocks and minerals are the same. They must also 

be free of differences due to meteorological factors, 

the time of measurement, and the accuracy of 

measurements. 

The majority of mineral deposits, although 

differing in mineralogical composition, have about 

the same content of radioactive elements as the 

country rock. Table 15 gives the average concentrations of radioactive elements in rocks, water, 

in the air in soil, and in the atmosphere. 

This table shows that the radioactivity of the 

seas and the rivers is about a thousand times less 

than that of soil. Also, the concentration of radon 

in the air of the soil is a thousand times greater 

than its concentration in the atmosphere. The 

distribution of radon in soil air may be studied by 

drawing the air directly into an ionization chamber. 

The concentrations of radioactive elements 

given for rocks, soil, and air are averages of 

many determinations. Single samples may differ 

considerably in their radioactivity, depending upon 

their petrochemical composition, location and other 

factors. A large number of determinations have 

shown that the radioactivity of acidic rocks is greater 

32 
Table 15.--Concentrations of the radioactive Elements 

Description of 

environment 

Concentration of radioactive elements of the 

uranium series 

Concentration of radioactive elements of the 

thorium series 

Soil 

Sea and river waters 

Soil air 

Atmospheric air 

Atmospheric air over the 

ocean away from the shores 

1-2 x 10-12g Ra/g 

2 x 10-15 g Ra/cm3 

2 x 10-10curies/1 

1 x 10-13 curies/1 

1 - 2 x 10-15curies/1 

1- 2 x 10-5 g Th/g 

10-8 dto 10-7g Th/cm3 

than that of basic rocks, although the difference is 

small and both types are within the same order of 

magnitude. 

Up to the present, radioactive methods have 

been applied only to uranium-radium and thorium 

ores, and to gases exhibiting radioactivity. However, 

radioactive methods may be used in prospecting for 

non-radioactive elements, which are paragenetically 

associated with radioactive elements that may serve 

as indicators. The methods can be used in the same 

manner for studying negative anomalies (prospecting 

for salt domes). 

We will now discuss the most important radioactive field methods. 

Emanation Method (Radon and Thoron) 

The emanation method of prospecting for mineral deposits, especially the radioactive ores, is 

based on the detection of gaseous radioactive emanations in the soil air. At present it is the most basic 

radioactive method. 

Radium and thorium emanations escape into 

the pores of the country rock, and are found as gases 

in the soil air where they take part in a gaseous exchange with the atmosphere. This exchange has not 

been thoroughly studied but it may be shown that 

decay of radioactive elements causes the emanations 

entering the atmosphere to be much greater than the 

emanations returning to the soil. In other words, 

the

. 

 process proceeds in one direction. 

In homogeneous rocks with a uniform radium 

content, the concentration of emanation in the rocks 

is directly proportional to the radioactivity of the 

rock and cannot exceed the concentrations of thorium 

and radium required for equilibrium. 

Radioactive objects distributed at different 

depths in the earth's crust will yield emanations in 

proportion to the concentration of radioactive elements within them. Therefore, the emanation 

concentration in the soil air will be greatest next 

to a radioactive object and will constantly decrease 

with distance from it. 

Diffusion usually causes the emanations to be 

carried away from the emanating object in the direction of decreasing concentration. This problem has 

33 

not been thoroughly studied from the quantitative 

point of view. In order to evaluate the emanation 

method as applied to different rocks, V. I. Baranov 

and Ye. G. Grachev (1933, 1937, 1938), A. G. 

Grammakov and N. M. Lyatkovskiy (1933), and 

A. G. Grammakov (1936) experimented with the 

method under laboratory conditions; also, G. V. 

Gorshkov, Ye. G. Grachev, and V. I. Baranov (not 

published) determined the diffusion coefficients for 

radium and thorium emanations in different rocks 

under field conditions. These data are given in 

table 16. 

To give an idea of the depth at which the 

emanation (radon) method will be effective, materials 

having different diffusion coefficients are presented 

in table 17; the distances from the emanating object 

have been calculated as a function of the diffusion 

coefficient and as fractions of the initial concentration of the radium emanation of the object. 

The values in this table have been computed 

for emanations from an infinite planar layer. 

(Grammakov,-A. G., Fizicheskie osnovy emanatsionnogo 

metoda.) 

The depth of detection by this emanation 

method depends upon the magnitude of the diffusion 

coefficient and the intensity of radioactivity of the 

radioactive object. The distance or depth is smaller 

than would be expected from a linear relationship. 

The depth of detection is several meters in sands, 

alluvium, and weathered or altered primary rocks. 

In dense, unaltered primary rocks and in stagnant 

environments it will be only several tens of centimeters. 

The ground water table represents the practical 

limit of depth. From depths greater than this, radium 

emanations cannot penetrate to the surface. However, 

the movement of ground waters may modify the dispersion pattern. 

The depth of detection for the thoron emanation 

method is considerably smaller (on the order of tens 

of centimeters) than that for the radon method because 

of the small half-life of thoron. However, the simplicity and dependability of thoron measurements 

performed on systematically collected samples of 

soil air, sometimes make the use of the thoron 

method practical for field work. 
Table 16. --Diffusion coefficients for radium and thorium emanations 

Type of rock Water content 

in percent 

Diffusion coefficient for 

radium emanations 

in cm /sec. 

Diffusion coefficient for 

thorium emanations 

in cm2/sec. 

Dry quartzitic sand 0.0 6.75 x 10-2 6.75 x 10-2 

Moist quartzitic sand 8.13 5.00 x 10-2 

Same 10.4 3.75 x 10-2 

Same 14.2 ----- 1.75 x 10-2 

Same 15.2 1.00 x 10-2 

Clayey sand dry 3.5 x 10-2 

Powdered clay dry 5x 10-2 

Mixture of clayey soil and 

quartz sand 

dry 3.5 x 10-2 

Tabosharskiy alluvium in 

summer months in natural 

conditions 

slightly 

moist 

7 x 10-2 ---- 

Altered and disintegrated slightly about 

Tabosharskiy granodiorite 

in natural conditions during 

the fall. 

moist 0.5 x 10-2 

Solid, unaltered granodiorite dry 10-4 

Water 1/ . at 18° C 1.15 x 10-5 Approximately of 

the same order 

Air 1/ 0.0 - 0.1 as those for radium 

1/ This data has been taken from the classical literature (Myer and Schweidler, 1927). 

Table 17. --Concentrations of radium emanations as a function of the diffusion coefficient and the 

distance from the source of the emanations 

Concentration of radium 

emanation in terms of 

the initial density of 

the emanating object 

Distance in meters from the emanating object [to the zonel of the 

given radium emanation concentration, for indicated values of the diffusion 

coefficient. 

1 x 10-2 

cm2/sec. 

4 x 10-2 

cm2/sec. 

7 x 10-2 

cm2/sec. 

1 0 0 0. 

1/2 0.48 0.98 1.26 

1/10 1.6 3.2 4.2 

1/100 3.2 6.5 8.35 

1/1000 4.8 9.8 12.5 

34 
We shall now examine the basic factors contributing to an emanation anomaly, and estimate 

the minimum concentration of radium required to 

produce an anomaly over a given ore deposit. The 

concentration of the emanations may be determined 

from the following expressions: 

N a A d 103curies/liter 

n 

where .a is the emanation coefficient 11/, A is the 

concentration of radium in the rock (rts of radium 

per parts of rock), d is the density of the rock, n 

is the porosity of the rock (Grammakov, A. G., 

Fizicheskiye osnovy emanatsionnogo metoda). 

It can be seen from this expression that the 

concentration emanation in rock is dependent not 

only on the concentration of radioactive elements 

but also on the density, the emanation coefficient 

and porosity of the rock. The density of rocks 

does not vary significantly (about twofold in the 

extreme cases) but the emanation coefficient and 

the porosity may vary greatly (from a fraction of 

a percent to several tens of percent). Therefore, 

it is impossible to determine a general concentration of emanation which would apply to all types of 

natural occurrences. 

Even at the same prospect and in the same 

type of rock having uniform concentrations of 

radioactive elements, the concentration of emanation in the soil air may vary owing, to changes in 

the emanation coefficient and the porosity according to the formula variation up to several tens of 

times are possible because either the emanation 

coefficient or the porosity may exhibit up to tenfold 

variation. Luckily, most rocks with a high porosity 

also have a high emanation coefficient so that the 

two tend to compensate one another. 

Up to the present the change in emanation 

concentration as a function of changes in porosity, 

the emanation coefficient, and density have not 

been measured. However, on the basis of indirect 

evidence (across unmineralized tectonic faults) it 

may be assumed that the emanation concentration 

may differ from its background value by a factor of 

ten. Therefore, an emanation anomaly with a 

tenfold increase above the background concentration 

does not necessarily indicate the presence of rocks 

with an increased concentration radioactive elements 

in them. 

Normally the emanation concentration for radium 

in the soil air at a depth of 0. 5 meters fluctuates from 

0.8 x 10-10to 5 x 10-10curies per liter. Thus, emanAtion anomalies with concentrations greater than 5 x 10' 

curies per liter are usually related to an increase in 

the concentration of radioactive elements within the 

rocks of the given area. 

We will give a brief description of emanation 

profiles, surface surveys, and anomalies. An emanation profile is a graph of the distribution of the emanation concentrations along a traverse (usually perpendicular to the trend of the rocks). The emanation concentrations are determined in soil air sampled at a definite 

depth (usually depths of 0. 5 or 1.0 meters are most 

practical). 

"Translators' note: "koeffitsient emanirovaniya"; exact English 

equivalent not known. 

35 

The direction of the traverse and the separation 

and depth of the soil air samples is determined from 

the geology of the area and from the type of vein and 

its depth (if this is known before beginning the survey). 

The depth of detection is estimated from the character 

of the rocks (alluvium, weathered rocks and others). 

A metal tube is used to collect the sample of 

soil air. It is inserted to a definite depth at each 

sampling location (for example, to a depth of one meter, 

or down to the layer dividing clays from gravels). The 

emanation concentration of the sample is recorded in 

curies per liter or soil air. 

The emanation concentration of the soil air over 

thorium prospects is determined by analyzing a current 

of soil air. 

The results are presented in the form of a graph. 

The sample points are plotted on the abscissa and the 

emanation concentrations are plotted on the ordinate. 

A geologic section is usually drawn beneath the abscissa 

at the same scale. 

A study of emanation profiles shows that fractures 

(joints, faults, and some veins), pegmatites, uraniumand thorium-bearing deposits, and several other types 

of veins show increased radioactivity in the 

soil in the form of maxima upon the profile graph. 

Sometimes the maxima appear as narrow sharp peaks 

and sometimes the curve increases gradually giving 

a broad maximum. The maxima may have many 

shapes. Often several small maxima may appear at 

the base of a large one. Groups of fissures or veins 

may display a group of peaks upon the profile. 

Field work is not usually limited to a few widely 

separated profiles, but the area to be examined is 

covered by a series of parallel profiles run at constant intervals. This is called an areal emanation 

survey. 

The results of an areal emanation survey are 

plotted upon a topographic base map of the area.. The 

zones of equal concentration are outlined by interpolating the data and drawing isograds through points 

of equal concentration. 

Obtaining emanation profiles sometimes requires 

a long period of time, during which the concentrations 

do not remain constant but are subject to changes due 

to meterological factors, the time of the year, and 

others. Because of this, control points are selected 

during the survey from which samples taken from time 

to time (daily during mass sampling). Fluctuations 

in the emanation concentrations of the control points 

must be taken into account in order to determine the 

approximate value of the radioactivity of different 

areas. 

The contour interval of the isograds is determined 

by the fluctuation in the concentrations and by the 

character and intensity of the radiometric anomaly. 

In his work on radioactive mineral deposits L. V. 

Komlev has suggested that only one isograd should 

be used in contouring the anomalies in Central Asia. 

This would outline those areas of high concentration 

which are independent of other factors. According 

to this system, areas of low concentration would be 

those which are affected by factors other than the 

concentration of radioactive elements (such as the 

emanation coefficient, density, and porosity). 
The scale of the sampling grid or the separation 

between the samples collected on traverse is important 

in the application of this method. Because of the large 

variety of conditions under which radioactive elements 

occur, only very general instructions can be given. 

Knowledge of the geology of the area is essential if 

the survey is to be correctly carried out. Theoretically, large zones of high concentration do not require 

as frequent sampling as small zones. Similarly, 

extensive deposits do not require as small an interval 

between traverses as do small lenticular deposits or 

tabular veins. 

Samples should not be collected more than 10 

meters apart between detritus, sands, or disintegrated 

rock (materials in which the emanation method is 

practical) have a radius of diffusion on the order of 

several meters. 

We conclude that an emanation survey is not a 

substitute for geologic studies, but when used correctly, can serve as a valuable auxiliary tool, increasing the effectiveness of the geologic studies and 

reducing the number of prospecting pits or trenches, 

especially in the areas that lack outcrops 12/. 

Gamma Method 

Gamma rays produced by radioactive elements 

have a greater penetrating power than X-rays. However, gamma ray profiles made from surface measurements will indicate the distribution of radioactive 

elements only to a depth of 30 centimeters. The depth 

of detection is much less than that of the emanation 

method, but interfering factors (weather conditions, 

emanation coefficient, and others) have a smaller 

effect on the results of a gamma ray survey. Practically all that the gamma ray method records is the 

concentration of radioactive elements in the rocks 

surrounding the instrument. Therefore, its use 

under field conditions is limited to the following types 

of problems: the association of ore deposits to radioactive rocks; the study of mineral deposits exposed 

in outcrops and trenches; the study of mineral deposits 

by means of underground workings and drill holes 

(gamma-ray well logging); a rough quantitative determination of the radioactivity of hand specimens of 

ore; a quantitative determination of the radioactivity 

of country rock from outcrops, drill holes, and 

underground workings. 

The most important application of the gamma 

method is in studying outcrops during the initial 

phases of prospecting a mineralized area. A study 

of the gamma activity of the outcrops is a reliable, 

accurate, and rapid method of determining areas of 

high radioactivity, which should be prospected in 

detail. In areas which are largely covered by detritus 

or porous, weathered and fractured rocks, it is expedient to determine the areas of high radioactivity 

by means of the emanation method. However, if 

both detritus and solid rock are present, the radio 

active areas should be located by the emanation 

method where there is detritus, and by the gamma 

method where there is solid rock. 

12The emanation method has been used successfully in prospecting 

for pegmatitic veins at Volyn in the Urals. The veins were covered by 

10 meters of sedimentary rocks in some places. (I. K. Polovko). 

A more detailed study of the area of high 

concentration is accomplished by making a gamma 

survey along traverses crossing outcrops or in 

trenches. Under favorable conditions it is best to 

make a detailed emanation survey. The distance 

between samples varies from 0. 5 to 10 meters 

depending upon the variation of radioactivity in the 

rocks. The interval between traverses varies from 

several meters to tens or hundreds of meters depending upon the geology. As in the emanation survey, 

the results of the gamma survey are plotted upon a 

topographic map and the zones of high radioactivity 

are colored or shaded. ("Normal radioactivity" is 

the radioactivity of the fresh rock in the given area.) 

It is determined by gamma ray measurerfients. 

By correcting for cosmic rays and the background 

of the instrument, the average radioactivity of the 

uppermost layers of rocks may be approximately 

determined.,This concentration is expressed in 

equivalents of U308 or in other units if more convenient. 

Measurements of gamma-ray intensity in 

subsurface workings permits one to determine the 

zones of high radioactivity and sometimes allows 

calculation of the radioactivity of the rocks and ores 

in terms of equivalents of U308. 

The gamma-ray instrument in this type of 

investigation is like a geologist's microscope, 

preventing him from making mistakes, as it records 

the radioactivity even where there is no visible thorium 

or uranium mineralization. 

Either an ionization chamber or a Geiger-Muller 

counter may be used in all of the problems listed 

above. It is important to note that the time required 

to make a measurement depends upon the radioactivity 

of the rock being tested. This time controls the accuracy of the measurements. The time required by the 

ionization chamber will not be the same as that of the 

counter. The ionization chamber will take slightly 

less time to measure rocks containing small amounts 

of radioactivity and will give highly accurate measurements. A Kolhurst ionization chamber, with a volume 

of four liters, will take about the same amount of time 

to measure rocks of normal radioactivity as will a 

counter, with an effective surface area of 100 sq. cm. 

Either instrument is accurate to within about 10 percent. The measurement of rocks that are ten times 

more radioactive than normal is made ten times 

f aster by using a counter instead of an ionization 

chamber; however, the measurement is only about 

50 percent accurate. The ionization chamber may 

be made very sensitive by using a gas at high pressure (usually argon), and the Geiger-Muller counter 

is made sensitive by increasing the effective surface 

area of the counter. (Up to the present no very good 

field counter has been developed; the Geiger-Muller 

counter has many imperfections.) The counter has 

been successfully applied to determine radioactivity 

in drill holes that penetrate mineral deposits. This 

is called "gamma well logging", being analogous to 

electrical well logging. 

The counter may be used to determine the 

equivalents of U308 or Th02 in radioactive ores. 

The accuracy of the determination depends upon a 

36 
uniform distribution of radioactive material within 

the container in which the measurements are made. 

To avoid large errors, the ore samples are usually 

placed into standard containers and measurements 

are made on different sides of the container. This 

permits determinations with an average error of 

about 20 percent to be made. 

The gamma method may be used to determine 

the radioactivity in equivalents of U308or Th02 in 

typical rocks occurring in outcrops, in mine workings, 

or in drill holes. The data may be analyzed for the 

purpose of solving geologic problems or for the purpose of prospecting for nonradioactive mineral 

deposits. This aspect of radioactive methods in 

general and of the gamma method in particular has 

not been studied from the practical point of view. 

Other Radioactive Methods 

The measurement of alpha radiation in rock 

has not been widely applied to field work and we will 

omit a discussion of this method. 

The measurement of the radioactivity of rocks 

in situ by means of beta rays has not been tried. 

Indirect geophysical radioactive methods of 

prospecting for mineral deposits should be mentioned. 

The most economical and rapid of these are the aspiration method of prospecting for radioactive minerals, 

and the method of determining beryllium in ores by 

means of the nuclear photo effect of beryllium 

(Baranov, 1926). In the aspiration method a number 

of radioactive samples (a geologic collection) are 

placed under a metal bell jar. The air is drawn out 

by a vacuum pump and pumped into the ionization 

chamber of an electroscope. The presence of radioactive elements is detected by an increase in the 

ionization current recorded by the electroscope. In 

the second method, the amount of beryllium in a 

sample of ore is determined by the radioactivity 

produced in silver (or some other indicator) by 

beryllium photo neutrons which have been showed by 

paraffin. Research has shown (Baranov, 1926) that 

by using an ampoule containing 50 mg of radium, the 

beryllium content of a sample may be determined with 

an error of only a tenth of a percent. 

Bibliography 

Aydarkin, Gorshkov, Grammakov, Zhadin, Kolchina, 

Novyy sposob opredeleniya berilliya v rudakh po 

foto-neytronam (New method for determining beryl 

in ores by photo-neutrons): being prepared for 

publication. 

Baranov, V. I. , 1926, K Teorii aspiratsionnogo 

poroda dlya issledovaniya geologicheskikh 

kollektsiy na radioaktivnost' (On the theory of 

aspiration of rock for examining geological specimens for radioactivity): Vestnik Geologicheskogo 

Komiteta, 1925g, No. 4, p. 58. 

Baranov, V. I. , and Gracheva, Ye. G., 1933, K 

Teorii emanatsionnoy razvedki (On the theory of 

emanation surveys): Trudy Radiyevogo Inst. , 

1933, no. 2, pp. 61-66. 

Baranov, V. I. and Gracheva, Ye. G., 1937, Trudy 

Radiyevogo Inst., no. 3, p. 117. 

Grammakov, A. G. and Lyatkovskaya, N. M.: Zhurn. 

geofiziki, 1935, 5 p. 290. 

Grammakov, A. G., Zhurn. geofiziki, 1936, p. 133. 

Grammakov, A. G., Gorshkov, Lyatkovskaya, 

Schetchik Geygera-Myullera i yego primeneniye 

v geologo-pazvedochnom dele (The Geiger-Willer 

counter and its application to geological problems) 

will be published in Izv., VGI. 

Grammakov, Gorshkov, Lyatkovskaya, Metodika 

izmereniy radioaktivnosti, gornykh porod 

schetchikami Geygera-Myullera (Method of 

measuring the radioactivity of rocks by the 

Geiger-Willer counter): will be published in Izv. 

VGI. 

Grammakov, A. G. , Fizicheskiye osnovy emanatsionnogo metoda (Physical principles of the emanation method): being prepared for publication. 

Gracheva, Ye. G., 1938, Vliyaniye struktury i 

poristosti porody na diffuziyu radioaktivnykh 

emanatsiy (The effect of structure and porosity of 

rocks on the diffusion of radioactive emanation): 

Trudy Gosudarstvennogo Radiyevogo Instituta, 

Tom 4, pp. 228-244. (See also Tray. inst. 

etat radium (U. S. S. R.- 7/o7-4, pp. 228-233) 

Meyer, Stefan, and Schweidler, Egon, 1927, 

Radioactivita, B. G. Teubner, Leipzig, 721 pp. 

Shpak, V. A.: Akad. Nauk SSSR, Doklady, 1937, 

16, No. 2, III. 

Appendix 

The development and specialization of radioactive methods has resulted in the determination of 

the absolute ages of geological formations. An excellent description of this is' given in I. Ye. Starik's 

latest book, "Radioactive Methods of Determining 

Geological Time": ONTI, Moscow, Leningrad, 1938, 

pp. 1-176. 

Radioactive methods are important because 

they can be used to determine the absolute ages as 

well as the relative ages of individual .formations. 

The determination of the absolute age of a mineral 

deposit permits us to determine its relation to 

tectonic processes and to paleogeographic conditions. 

This enables us to determine the origin of the formations. A determination of the age of minerals of 

the Khibinsk mountains indicates that it is necessary, 

while exploring for fissured rocks on the Kol'skiy 

Poluostrov [Kola Peninsula), to search for tectonic 

features produced in the Hercynian. The attempt 

of V. P. Savchenko to determine the age of oOlites 

at the surface is interesting and has practical 

significance. 

Further investigations into the applications 

of radioactive methods for age determination 

will be of importance in prospecting in the 

future. 

37 INT . -DUP . SEC . , WASH.,D.C.19440