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Role of mining geologist in explorationModern-day mining geologists may have been educated as geological engineers as

geoscientists. If the degree is in geological engineering, a curriculum in engineering science,

geosciences, geotechnics, mining, and economics has provided him or her with a variety of

capabilities that extend from exploration to the development and utilization of minerals. If

the degree is in geosciences, a background in the physical and natural sciences, ore petrology,stratigraphy, and geomorphology affords a basis for a deeper understanding of the geological

characteristics of mineral deposits. When geologists of either background enter the mining

profession and make the best use of their experiences, their capabilities broaden and deepen

according to their natural talents to a point where the wording on the diploma is immaterial.

Deepening becoming a specialist may require postgraduate study and additional

diplomas. In any event, college residence is a preparatory step; professional work and

professional growth define the career.

Mining geologists have a powerful set of tools and concepts at their disposal, and many or

these are associated with the unprecedented - even frightening growth of all technology and

science in this century. These are the tools and concepts that are described in the remainderof this lecture notes; they reflect an almost overwhelming range in genetic models for ore

deposits, an integration of geology and geophysics, the appearance of exploration

geochemistry, a revolution in logistics, and the appearance of an entire new group of

computer assisted sciences.

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CLASSIFICATION OF ORE RESERVES

Classes of Ore Reserves: Paradoxically enough, no one can be sure how much ore there is

in a mine until it has been mined out; therefore, at best, ore reserve figures are estimates

rather than certainties. The tonnage of ore that is exposed on all sides by workings can be

calculated with reasonable accuracy, but the tonnage that exists beyond or below anyworkings can be estimated only by making certain assumptions. It is, therefore, conventional

to divide the ore reserve into categories based on the degree of assurance of its existence. Of

several classifications that have been proposed, all based on the same principle, the oldest

and probably the most widely used divides the ore reserve into three classes as follows:

1. Positive Ore or Ore Blocked Out. Ore exposed and sampled on four sides, i.e., by levels

above and below and by raises or winzes at the ends of the block. This definition applies to

veins; for wide ore bodies the workings must be supplemented by crosscuts.

2. Probable Ore: Ore exposed and sampled either on two or no three sides. (Authorities

differ.)

3. Possible Ore (geologists ore): Ore exposed on only one side, its other dimensions being

a matter of reasonable projection. Some engineers use an arbitrary extension of 50 to 100

feet. Others assume extension for half the exposed dimension.

Although these definitions are relatively rigid, they fail to specify one important factor - the

distance between the workings that expose the ore. This factor is pertinent because there is

always a chance that somewhere within the block there may be a barren patch, and this

chance is greater as the distance between exposures is greater. Therefore, in order that ore

may be considered Proved orBlocked Out, the workings in which sampling has been done

should not be more than some specified distance apart; yet no arbitrary standard can be set

up, because different types of ore vary in their regularity and dependability. In a spotty

erratic ore body the spacing must be closer than would be permissible in a large uniform ore

body., In a general way a fair rule in gold quartz veins below influence of alteration is

that no point in the block shall be over fifty feet from the points sampled. In limestone

or andesite replacements, as by gold or lead or copper, the radius must be less. In

defined lead and copper lodes, or in large lenticular bodies such as the Tennessee

copper mines, the radius may often be considerably greater, - say one hundred feet. In

gold deposits of such extraordinary regularity of values as the Witwatersrand Bankets,

it can well be two hundred or two hundred and fifty feet.

The regularity of the ore determines not only the maximum permissible spacing, but also the

number of sides on which the ore must be exposed in order to assure its presence.

Although ore of an erratic nature needs to be blocked out on four sides, as called for in the

conventional definition of positive ore, a uniform ore body whose structure is well

understood might be counted on with reasonable confidence if it were exposed on only two

sides. Hoover, therefore, proposed categories based on more flexible definitions which allow

some leeway to the judgment of the individual:

Proved ore: Ore where there is practical no risk of failure of continuity.

Probable Ore: Ore where there is some risk yet warrantable justification for assumption ofcontinuity

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Prospective Ore: Ore which cannot be included as Proved or Possible, nor definitely

known or stated in any terms of tonnage.

Another set of terms, which allow rather wide latitude to the individual, has been adopted by

the U.S. Geological Survey and the U. S. Bureau of Mines. Instead ofProved, Probable, and

Prospective, these Bureaus useMeasured,Indicated, andInferred, defined as follows:

Measured ore is ore for which tonnage of computed from dimensions revealed in outcrops,

trenches, workings, and drill holes, and for which the grade is computed from the results of

detailed sampling, and measurements are so closely spaced, and the geologic character is

defined so well, that the size, shape, and mineral content are well established. The computed

tonnage and grade are judged to be accurate within limits which are stated, and no such limit

is judged to differ from the computed tonnage or grade by more than 20 per cent.

Indicated ore is ore for which tonnage and grade are computed partly from specific

measurements, samples, or production data, and partly from projection for a reasonable

distance on geologic evidence. The sites available for inspection, measurement, and sampling

are too widely or otherwise inappropriately spaced to outline the ore completely or toestablish its grade throughout.

Inferred ore is ore for which quantitative estimates are based largely on broad knowledge of

the geologic character of the deposit and for which there are few, if any, samples or

measurements. The estimates are based on an assumed continuity or repetition for which

there is geologic evidence; this evidence may include comparison with deposits of similar

type. Bodies that are completely concealed may be included if there is specific geologic

evidence of their presence. Estimates of inferred ore should include a statement of the special

limits within which the inferred ore may lie.

This classification leaves room for considerable deduction from geological background. It is

well suited to its tended purpose, the estimation of the reserves of a district or a nation. It is

less satisfactory for valuing a single mine.

McLaughlin classification of ore deposits according to the assurance of ore supply that

they are ordinarily capable of providing with the amount of exploration that is customary

in good current practice". According to the categories of risk involved sets up three classes:

I. Plenemensurate ore bodies those capable of being fully measured and sampled at an

early stage in the operations.

II. Partimensurate ore bodies those in which prospects for ore in addition to proved

reserves remain a substantial element until the later stages of the life of the mines based onthem.

III. Extramensurate ore bodiesthose difficult to explore and measure much in advance of

mining, in which the value of prospects for ore based on geologic evidence exceeds the value

of proved reserves throughout most of the life of mines supported by them.

Class I includes most placer deposits and other ore bodies which have definite bottoms,

whether limited by the depth of oxidation or enrichment as in the case of lateritic bauxite ores

and most porphyry coppers, or by shallow structural bottoms as at Cobalt, Ontario, or

bounded by property lines as in the outcrop mines of the Rand.

Class II includes a great variety of ore deposits which have in common the characteristic thatthe ore is likely to extend much farther or deeper than the limits to which development can

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economically be carried at any one time, or that even if individual ore bodies have been

delimited there is good reason to expect that new ones will be found beyond such limits.

Class III includes deposits whose extension or repetition depends almost wholly on

geological evidence. Such deposits rarely have large developed ore reserves and could be

assigned only a moderate value on conventional methods of estimation. They periodically

face the danger of exhaustion yet they may, nevertheless, enjoy long and profitable lives ifbold and intelligent development is kept well ahead of extraction. Among such deposits are

some of the massive sulphide copper mantos of Morococha, Peru; similar lead-zinc-silver

mantos and pipes of Tintic, Utah; and small, structurally controlled ore bodies such as those

of Bendigo, Victoria.

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MINERAL EXPLORATION PROCEDURES AND APPLICATION

OF EXPLORATION TECHNIQUES ON MINERAL AND COAL DEPOSITS

The role of Programming in mineral exploration Procedures forms a vital and initial step

towards scientific investigation. Modern exploratory activity can be relatively complex,

involving several or many different sorts of work, often by different people over a relatively

long period of time.

There is often a need to evaluate the rate of progress, the suitability of technique, and the

degree of encouragement provided by the results. It is quite unlike individualistic work such

as the lone prospector used to do. Consequently, major benefits arise from the explicit

definition of the work to be done, i.e. the tools to be used, the sequence in which they are to

be used, decisions necessary before commitment to certain courses of action and so on.

Stated programs of work are helpful to the person directly in charge because they help him to

see the job in perspective, draw attention to the need for resources, the need to communicate

and the need to co-ordinate etc. They usually tend to focus attention on certain vital stages at

which favourable assessments of the results to hand are necessary or desirable before

initiation of dependent or subsequent activities.

Programmes of work are helpful to supervisors because they enable a definite understanding

of the work to be done and usually assist comprehension of why. They provide a basis for

intelligent interest, periodical review, and discussion without excessive involvement in or

distraction by detail.

Programs are helpful to the individuals directly concerned with limited parts of the projects

because they help generate the feeling of being part of a team with a definite purpose, the

achievement of which can be a major source of satisfaction. They emphasise the need for co-

ordination and communication at a level where these aspects are often deficient, and permit

individuals to recognise their part in proper perspective with respect to the overall job.

Thus programs are helpful to , and at, all levels of the organization.

Perhaps most importantly of all programmes is the foundation for schedules, and

programmes and schedules are fundamental to control. Without control, resources cannot be

expended with optimum efficiency, and this reduces the likelihood of success and therefore

the realisation of the objective justifying the whole venture.

A simple programme typical of many and stated very broadly might be as follows:

(a) Selection of area by broad geological considerations,

(b) Acquisition of area for exploration activities,(c) Reconnaissance exploration, possibly by broad geochemical, geological and geophysical

methods,

(d) Selection of areas of particular interest as indicated by the reconnaissance work,

(e) Detailed local geological ,geochemical and geophysical work,

(f) Conclusive activities such as costing, drilling, shaft sinking etc.

(g) Feasibility studies,

(h) Decision to mine, hold for future or surrender,

(i) Appropriate action.

As each project has its own particular characteristics, the program should be chosen to fit it

individually, and as each frequently is of different merit compared to others, this mayinfluence the resources and hence the methods employed.

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GUIDES IN MINERAL EXPLORATION

(i) Geochemical guides (ii) Groundwater as a guide

(iii) Geo-botanical and Bio-chemical guides.

Geochemical Guides

Proximity to an ore body is indicated in some instances by the presence of metallic ions in

rocks, soil or groundwater. Even though the element in question may be present in traces sosmall as to be detectable only by delicate chemical tests, a map showing its distribution may

disclose target rings surrounding an ore body.

Groundwater as a Guide

Groundwater in a mineralized region, especially where sulphides are undergoing oxidation,

contains metals and sulphates in amount ranging from traces to so much that the water is

undrinkable. If metals are present in the water, they are likely to be absorbed by the limonite

or by the manganese dioxide associated with it, and show up as traces on analysis. Such

metals may include Cu, Zn, Pb, Ni, Co, Mo, W, Sb, and Bi.

Geobotanical and Biochemical GuidesThe possibility of using vegetation as a guide to ore depends; firstly (and probably least in

importance), on the suggestion that metals and other elements may modify the appearance of

foliage; secondly, on the fact that certain elements play a role in determining what species of

plants which are able or unable to grow in a given place; and then, on the well-established

observation that certain plants can take up and concentrate elements selectively from soil

solutions.

Some species of plants are poisoned by certain elements in the soil, while others, if they do

not actually thrive on the same substances, are at least able to tolerate them and thus grow

more abundance where competition is lacking.

Rock Alteration-An important factor for observation.

1. Nature of Alteration as a guide

The mineralogical changes that are so common in rocks surrounding epigenetic ore deposits

usually involve the introduction of certain chemical elements and the removal of others, but

occasionally the chemical change is negligible and the elements that were present originally

merely rearrange themselves into new assemblages of minerals. In monomineralic rocks,

such as pure limestones and sandstones, the few elements present do not provide the makings

of new minerals and in the absence of introduced material, alteration is recognizable only by

difference in texture or colour.

Common alteration minerals characteristic of various types of mineralization are:

(a) With hypothermal mineralization: garnet, amphiboles, pyroxenes, tourmaline, biotite

(b) With meso-thermal mineralization (and also in many deposits classed as hypothermal and

epithermal): sericite, chloride, carbonates, and silica.

(c) With epithermal mineralization: some sericite, often much chloride and carbonate,

adularia or alunite.

2 Hypogene Zoning as a Guide

All of the foregoing mineralogical variations might be regarded as aspects of hypogene

zoning, but zoning in the stricter sense the progressive change in mineralization along

channel ways from source to surface or outward from a central axis is serviceable in asomewhat different way. It finds its chief usefulness in the epithermal and the shallower of

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the mesothermal deposits, where noticeable changes may take place either laterally within the

limits of a single companys holding or in depth within the limits accessible to mining.

At horizons above the top of the ore zone the vein fracture is often a mere slip .

Sparse quartz starts to come in with depth, usually at a narrow stringer along the slip. The

quartz increases rapidly with depth and the top of the ore zone lies not far below the top of

the quartz. Base sulphides are sparse here .. Base sulphides increase with depth and reach amaximum at the heart of zone. Fragments of wall rock cemented by vein matter become

abundant at this horizon; many are completely replaced by silica and sulphides.

Here the vein attains its maximum width and this width usually continues to the lowest

explored horizon.

3 OXIDATION PRODUCTS

The oxidation products of an ore body constitute a type of guide that has been used

effectively by miners and prospectors since time immemorial, but modern understanding of

the chemistry and geology of oxidation have made it even more effective.

Metals in the Oxidized zonesGold

Of the familiar metals, gold is the most resistant to weathering. Particles of native gold

accumulate in fractures and voids in the rock and often produce spectacularly high assays at

the immediate surface. In addition, chemical leaching of associated material tends to

concentrate the gold. For these reasons, high gold values in the top few feet of the oxidized

zone are not to be taken too seriously. They demand attention, of course, but there is little

fear that they will fail to receive it.

Gold is not complete insoluble; it is converted into soluble chloride by nascent chlorine for

whose generation the requisite chemicals are present in oxidizing deposits :sulphuric acid is

always available, manganese dioxide is common, especially in leptothermal deposits, and

salts is at hand, particularly in arid climates. Accordingly, many instances of migration of

gold in the presence of manganese have been described. But as a rule the migration is local

and produces small rich seams and pockets rather than a well defined zone of enrichment.

However, there are a few well-authenticated cases of a thin supergene gold zone at the top of

a massive pyrite or pyrrhotite body.

Other metals found in the oxidized zone are tin, lead, zinc, copper, silver, nickel, cobalt,

molybdenum and chromium.

STRATIGRAPHIC AND LITHOLOGIC GUIDESIf ore occurs exclusively in a given sedimentary bed, the bed constitutes an ideal stratigraphic

guide. Less perfect, but still serviceable as a guide is a bed or group of beds which contains

most of the ore bodies even though other stratigraphic horizons may not be entirely barren. If

the containing rock is not a sedimentary formation but an intrusive body or a volcanic flow,

the same principles are applicable so far as ore search is concerned, but since in such cases

the guide cannot properly be called stratigraphic, the term lithologic is more appropriate. The

ore may be syngenetic (an original part of the body of rock) or it may be epigenetic

(introduced into the rock)

1 In Syngenetic Deposits

If the ore is an original part of a body of rock, the rock itself will serve as a guide; that is theore will be found within the particular rock formation and will be absent outside it. The

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location is most precise in layered rocks especially sediments but it is definite enough to be

useful even in homogeneous igneous rocks If the ore consists of a bed in a sedimentary

formation one need only know the stratigraphic sequence and the structure of the beds in

order to predict where the outcrop will be found or at what depth the ore will be at any given

place. For this purpose a structure contour map is the most convenient device for depicting

the shape of the ore bed and projecting its position.

Syngenetic deposits of igneous origin are usually less regular than sedimentary beds.

However in some thick sills and lopoliths, the rock constituents have a very regular

stratiform arrangement.

2 In Epigenetic deposits

Ore that has been introduced into rocks may show strain partiality to certain formations

whether the ore follows fractures or replaces formations bodily. Replacement ore bodies

differ from most sedimentary (syngenetic) deposits in that not all of the favourable stratum is

ore; replacement within the bed is often controlled by some additional loci which may consist

of fold axes.

The rocks most receptive to gold seem to be those which contain chloride or other minerals

of similar composition, although chlorite in the immediate vicinity of the ore is often altered

to sericite. There are more gold deposits in chloritic slates and phyllites and in basic to

intermediate igneous rocks than in quartzites, rhyolites or limestones.

3 Competent vs. Incompetent Formations

In some districts, at least competent rocks are more hospitable hosts to ore than incompetent

ones, and surely this is what would be expected from their mode of failure in fracturing.

Competent as the term is used here, refers to rocks that are relatively strong but, when they

do fail, break as though they were brittle material. Incompetent refers to rocks which are

weak and have a tendency to deform plastically or by flow. Under most conditions quartzites,

conglomerate and fresh igneous rocks are competent. Incompetent are shales, slates , schist

and limestone also igneous rocks that have been altered to sericite, chloride or serpentine.

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(i) Ground Geophysics

One of the principal advantages to ground electrical surveys is their capability of making

direct contact with the earth. For this reason, electrical methods are widely used in detailed

exploration for ore bodies. Ground magnetic methods, like aeromagnetic methods, are used

as aids to geologic mapping as well as in searching for ore bodies.

Ground electromagnetic methods are in general use where massive sulphide deposits aresought; as with airborne electromagnetics, there are dozen of separate techniques. Ground

radiometric surveys are not as often applied to geologic mapping as are airborne radiometric

surveys; instead, their main use is in searching for uranium ore bodies. Gravity methods are

applied to regional geologic mapping, and they have a flow-up or supporting function in the

interpretation of other geophysical anomalies where gravity and magnetic response from an

iron ore body are compared. One use of gravity geophysics, and of refraction seismic

methods as well, is determining the depth and configuration of bedrock in alluvium-covered

areas.

(ii)Airborne magnetometer survey (Aeromagnetics)

The airborne magnetometer is the most important new tool in mining exploration. This newairborne method is developed as the result of construction of more sensitive instruments and

has proved to be a distance cost advantage as well as increasing chances for one discovery.

A typical recent discovery was the large magnetite deposits in Labrador, Canada. Magnetic

peaks or highs over an iron ore deposit were recorded by the airborne magnetometer. In a

number of cases, the magnetic data so recorded was so positive that ground survey parties

were despatched within twenty-four hours of the survey flights.

Many large mining companies are at present using this instrument in finding deposits or iron,

nickel, titanium and asbestos.

(iii) Electromagnetic Method

This is an important development in the field of airborne geophysics. In principle, the survey

is carried out by creating an alternating electromagnetic field from a large coil around the

fuselage. During the flight of the plane, this electromagnetic field induces secondary

alternating fields in the portion of the ground passed over by the plane. These secondary

fields vary in intensity and travelling time depending on the distance to and the conductivity

of the ground. The effects of these fields are recorded in a special receiving unit built into the

aircraft wings. By the airborne electromagnetic method, it is possible to detect sulphide ore

bodies, shear zones and other structures of economic importance.

Ground methods:

(i)Gravity Methods

The purpose of gravity surveys is to measure small local variations (anomalies) in the force

of gravity, as cased by geologic features as anticlines, salt domes, faults and dikes. The

application of this method like all other geophysical methods is based upon the difference in

the physical properties of different materials relative to one another. A salt some for instance

is composed of lighter materials than the surrounding sediments and this will usually give a

slightly smaller gravitational force than the surrounding sediments. In the case of an igneous

body the gravitational force would be larger.

In as much as the geologic features are very small compared with the earths volume, theanomalies produced are of small magnitude. Thus it has been necessary to develop very

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sensitive instruments to record these very small changes in the total force of gravity.

Pendulums torsion balance and gravimeters are used in most gravity surveys.

(ii) Magnetic Methods

Magnetic exploration is the oldest geophysical method. Magnetic exploration is based upon

the variations of the earths magnetic field caused by varying magnetic properties in

subsurface rocks.

In mining exploration, magnetic methods have been employed chiefly in the search for

magnetic minerals like magnetite, chromite and pyrrhotite. Magnetic prospecting is less

useful in areas of sedimentary rocks and in petroleum exploration except to locate basement

structures. The instruments employed in magnetic methods are the dip needle, horizontal and

vertical magnetometers.

(iii) Seismic Methods

Seismic methods are the most widely used of all current geophysical techniques, especially in

oil exploration. Seismic prospecting uses waves which are artificially produced by explosions

just below the surface. These waves are returned to the surface by either reflection orrefraction. From the examination of the time required for the waves to reach the detectors

placed at various point on the surfaced, it is possible to determine the depth and structure of

the underlying strata.

With the awakened interest in oil under the continental shelves, seismic prospecting has been

expanded into off shore areas. Although the seismic methods of prospecting have been highly

acclaimed in the petroleum industry , they are of very little use in mining exploration.

(iv) Electrical Methods

The electrical methods of prospecting are divisible into two groups (a) Self potential methods

that measure the natural electrical potential of the ground and (b) Induction methods which

measure the currents and potentials applied artificially into the ground.

The self potential method measures the natural potential in the ground developed as the result

of electrochemical action between minerals (especially sulphides) and ground water solutions

with which they come into contact. This method is useful in the search for sulphide ore

bodies. In the induction method, the current is forced into the ground, and measured.

Electrical methods do not penetrate into great depths like some other geophysical tools;

consequently, they are not used to any extent in oil exploration. Their most useful application

is in the search for shallow mineral deposits. In addition, electrical methods are applied inengineering geology where the depth of bedrock can be located for prospective dam site and

locations for other engineering projects.

(vi) Geothermal Methods

It is a well-known fact that the temperature in the earths crust increases with depth. The

usual rate of increase is about 10 C in 30 meters. The method uses resistance thermometers

which are lowered into the ground. The recorded temperatures are converted into gradients.

These temperature logs are valuable in indicating the presence of water and gas flow in oil

wells.

(v) Radiometric methods

With the development and production of nuclear energy, there is a worldwide exploration foruranium and thorium.

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The unique property (radioactivity) possessed by uranium and thorium minerals has made

prospecting for these minerals relatively less difficult. Radiometric methods defect such

radioactivity.

The instruments used in radiometric prospecting are the Geiger counter and the Scintillation

counter. Many major discoveries of rich uranium deposits throughout the world are attributed

to radiometric methods.

Diamond Core Drilling in exploration

Diamond core drilling is the most versatile of all methods, and it is designed specifically for

mineral exploration. Diamond drilling is relatively expensive, but it can be done in most

surface and underground locations and holes can be directed at any angle. It is the only

method capable of providing a complete record of geologic structure and rock texture. It is

also the only commonly used method that will deliver samples for geo-mechanics testing.

Even though diamond drilling has broad capabilities, it has limitations. Some kinds of broken

and abrasive rocks are nearly impossible to core at a reasonable cost.

There are special methods for recovery of core in soft rock (protective sheaths and tubes), butrecovery is generally poor in soft or thoroughly sheared zones. Careful use of drilling mud

aids core recovery, but if recovery is still too low, it may be necessary to collect sludge (bit

cuttings) as well as core. Sludge makes a less reliable sample than core, but it is often saved

as a matter of insurance until the core is recovered.

In diamond drilling the sample is cut by a diamond-armoured bit, recovered in the inner tube

of the core barrel, and brought to the surface. In wire-line diamond drilling, the most widely

used methods the inner tube is hoisted through the drill rods without removing the rods from

the hole. The circulating medium may be diesel fuel where a delicate permafrost condition or

water-soluble rocks are involved, but in most areas it is water with various combinations of

mud and other additives, which lubricate the bit and core, stabilize and seal the hole walls,

and carry the cuttings to the surface. Mud engineers are important consultants to drilling

projects, and their work is much more sophisticated than the title indicates.

Although geologists would prefer to have the largest possible core for study, a small-

diameter core is generally accepted since the cost of diamond coring increases with hole

diameter as well as with depth. Also smaller the core diameter, the greater is the attainable

depth with small, less-expensive, portable drill rigs. In continental Europe, core size is

expressed directly in millimetres; in English-speaking countries, the letter code designation

below in more common.

Size Code Core Diameter

(mm)

Hole Diameter (mm)

XR 18.3 30

EX 21.4 36

EXT 23.8 36

AX 29.4 47

AXT 32.5 47

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BX 42.1 59

NX 54.8 75

Geo-techniques LoggingIn addition to the data given in geologic logs, geotechnical logs require more detail on

discontinuities and they may require an estimate of rock strength. The angle between a

discontinuity and the axis of the core is measured in a special rock mechanics goniometer or

more crudely with a simple clinometer made from a celluloid protector.

The absolute orientation of a series of discontinuities can sometimes be calculated from their

attitudes in two or three non parallel drill holes or by taking an oriented core from one drill

hole; all of these techniques are explained and illustrated in a book on geological engineering

by Goodman (1976). Discontinuities can sometimes be oriented from geophysical logs in a

single hole, or they can be seen in an oriented borehole camera picture. The orientation of

drill-core information is especially important in mine design; in as much as none of the

existing techniques is entirely satisfactory, there is considerable emphasis on the

development of better tools.

Rock strength information is obtained from unsplit pieces of core. It is also expressed in core

logs by rock quality designation (RQD). A format of geotechnical logs is shown in Figure

(5.1); this log form is taken from a comprehensive report on the logging of rock cores for

engineering purposes.

Special hydrologic tests can be made by keeping exploration drilled holes open for use as

observation wells or by pumping water into open sections of exploration drill holes that havebeen seal off by packers.

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