Getting Gold: a practical treatise for prospectors, miners and students

CHAPTER II
GOLD PROSPECTING—ALLUVIAL AND GENERAL

It is purposed in this chapter to deal specially with the operation of searching for valuable mineral by individuals or small working parties.

It is well known that much disappointment and loss accrue through lack of knowledge by prospectors, who with all their enterprise and energy are often very ignorant, not only of the probable locality, mode of occurrence, and widely differing appearance of the various valuable minerals, but also of the best means of locating and testing the ores when found. It is for the information of such as these that this chapter is mainly intended, not for scientists or miners of large experience.

All of us who have had much to do with mining know that the majority of the best mineral finds have been made by the purest accident; often by men who had no mining knowledge whatever; and that many valuable discoveries have been delayed, or, when made, abandoned as not payable, from the same cause—ignorance of the rudiments of mineralogy and mining. I have frequently been asked by prospectors, when inspecting new mineral fields, what rudimentary knowledge will be most useful to them and how it can be best obtained.

If a man can spare the time a course of lessons at some accredited school of mines will be, undoubtedly, the best possible training; but if he asks what books he should read in order to obtain some primary technical instruction, I reply: First, an introductory text-book of geology, which will tell him in the simplest and plainest language all he absolutely requires to know on this important subject. Every prospector should understand elementary geology so far as general knowledge of the history of the structure of the earth's crust and of the several actions that have taken place in the past, or are now in operation, modifying its conditions. He may with advantage go a few steps further and learn to classify the various formations into systems, groups, and series: but he can acquire all that he need absolutely know from this useful little 2s. 6d. book. Next, it is advisable to learn something about the occurrence and appearance of the valuable minerals and the formations in which they are found. For all practical purposes I can recommend Cox and Ratte's "Mines and Minerals," one of the Technical Education series of New South Wales, which deals largely with the subject from an Australian standpoint, and is therefore particularly valuable to the Australian miner, but which will be found applicable to most other gold-bearing countries. I must not, however, omit to mention an admirably compiled multum in parvo volume prepared by Mr. G. Goyder, jun., Government Assayer and Assay Instructor at the School of Mines, Adelaide. It is called the "Prospectors' Pocketbook," costs only one shilling, is well bound, and of handy size to carry. In brief, plain language it describes how a man, having learned a little of assaying, may cheaply provide himself with a portable assay plant, and fluxes, and also gives considerable general information on the subject of minerals, their occurrence and treatment.[*]

It may here be stated that some twelve years ago I did a large amount of practical silver assaying on the Barrier (Broken Hill), which was not then so accessible a place as it is now, and got closely correct results from a number of different mines, with an extemporised plant almost amusing in its simplicity. All I took from Adelaide were a small set of scales capable of determining the weight of a button down to 20 ozs. to the ton, a piece of cheese cloth to make a screen or sieve, a tin ring 1 1/2 in. diameter, by 1/2 in. high, a small brass door knob to use as a cupel mould, and some powdered borax, carbonate of soda, and argol for fluxes; while for reducing lead I had recourse to the lining of a tea-chest, which lead contains no silver—John Chinaman takes good care of that. My mortar was a jam tin, without top or bottom, placed on an anvil; the pestle a short steel drill. The blacksmith at Mundi Mundi Station made me a small wrought iron crucible, also a pair of bent tongs from a piece of fencing-wire. The manager gave me a small common red flower pot for a muffle, and with the smith's forge (the fire built round with a few blocks of talcose schist) for a furnace, my plant was complete. I burned and crushed bones to make my bone-dust for cupelling, and thus provided made nearly forty assays, some of which were afterwards checked in Adelaide, in each instance coming as close as check assays generally do. Nowadays one can purchase cheaply a very effective portable plant, or after a few lessons a man may by practice make himself so proficient with the blowpipe as to obtain assay results sufficiently accurate for most practical purposes.

Coming then to the actual work of prospecting. What the prospector requires to know is, first, the usual locality of occurrence of the more valuable minerals; secondly, their appearance; thirdly, a simple mode of testing. With respect to occurrence, the older sandy and clay slates, chlorite slates, micaceous, and hornblendic schists, particularly at or near their junction with the intrusive granite and diorite, generally form the most likely geological country for the finding of mineral lodes, particularly gold, silver and tin. But those who have been engaged in practical mining for long, finding by experience that no two mineral fields are exactly alike in all their characteristics, have come to the conclusion that it is unwise to form theories as to why metals should or should not be found in certain enclosing rocks or matrices. Some of the best reef gold got in Victoria has been obtained in dead white, milky-looking quartz almost destitute of base metal. In South Australia reef gold is almost invariably associated with iron, either as oxide, as "gossan;" or ferruginous calcite, "limonite;" or granular silica, conglomerated by iron, the "ironstone" which forms the capping or outcrop of many of our reefs, and which is often rich in gold.

But to show that it is unsafe to decide off-hand in what class of matrix metals will or will not be found, I may say that in my own experience I have seen payable gold in the following materials:—

Quartz, dense and milky, also in quartz of nearly every colour and appearance, saccharoidal, crystalline, nay, even in clear glass-like six-sided prismatic crystals, and associated with silver, copper, lead, arsenic, iron as sulphide, oxide, carbonate, and tungstate, antimony, bismuth, nickel, zinc, lead, and other metals in one form or another; in slate, quartzite, mica schist, granite, diorite, porphyry, felsite, calcite, dolomite, common carbonate of iron, siliceous sinter from a hot spring, as at Mount Morgan; as alluvial gold in drifts formed of almost all these materials; and once, perhaps the most curious matrix of all, a small piece of apparently alluvial gold, naturally imbedded in a shaly piece of coal. This specimen, I think, is in the Sydney Museum. One thing, however, the prospector may make sure of: he will always find gold more or less intimately associated with silica (Quartz) in one or other of its many forms, just as he will always find cassiterite (oxide of tin) in the neighbourhood of granite containing muscovite (white mica), which so many people will persist in terming talc. It is stated to be a fact that tin has never been found more than about two miles from such granite.

From what has been said of its widely divergent occurrences it will be admitted that the Cornish miners' saying with regard to metals generally applies with great force to gold: "Where it is, there it is": and "Cousin Jack" adds, with pathetic emphasis, "and where it is generally, there I ain't."

I have already spoken of the geological "country rock" in which red gold is most likely to be discovered—i.e., the junction of the slates and schists with the igneous or metamorphic (altered) rocks, or in this vicinity. Old river beds formed of gravelly drifts in the same neighbourhood may probably contain alluvial gold, or shallow deposits of "wash" on hillsides and in valleys will often carry good surface gold. This is sometimes due to the denudation, or wearing away, of the hills containing quartz-veins—that is, where the alluvial gold really was derived from such veins, which, popular opinion to the contrary, is not always the case.

Much disappointment and loss of time and money may sometimes be prevented if prospectors will realise that all alluvial gold does not come from the quartz veins or reefs; and that following up an alluvial lead, no matter how rich, will not inevitably develop a payable gold lode. Sometimes gold, evidently of reef origin, is found in the alluvial; but in that case it is generally fine as regards the size of the particles, more or less sharp-edged, or crystalline in form if recently shed; while such gold is often of poorer quality than the true alluvial which occurs in mammillary (breast-like) nuggets, and is of a higher degree of purity as gold.

The ordinary non-scientific digger will do well to give credence to this view of the case, and will often thereby save himself much useless trouble. Sometimes also the alluvial gold, coarser in size than true reef-born alluvial, is derived almost in situ from small quartz "leaders," or veins, which the grinding down of the face of the slates has exposed; these leaders in time being also broken and worn, set free the gold they have contained, which does not, as a rule, travel far, but sometimes becomes water-worn by the rubbing over it of the disintegrated fragments of rock.

But the heavy, true alluvial gold, in great pure masses, mammillary, or botryoidal (like a bunch of grapes) in shape, have assuredly been formed by accretion on some metallic base, from gold salts in solution, probably chloride, but possibly sulphide.

Nuggets, properly so-called, are never found in quartz lodes; but, as will be shown later, a true nugget having all the characteristics of so-called water-worn alluvial may be artificially formed on a small piece of galena, or pyrites, by simply suspending the base metal by a thread in a vessel containing a weak solution of chloride of gold in which a few hard-wood chips are thrown.

Prospecting for alluvial gold at shallow depths is a comparatively easy process, requiring no great amount of technical knowledge. Usually the first gold is got at or near the surface and then traced to deep leads, if such exist.

At Mount Brown Goldfield, N.S.W., in 1881, I saw claimholders turning out to work equipped only with a small broom made of twigs and a tin dish. With the broom they carefully swept out the crevices of the decomposed slate as it was exposed on the surface, and putting the resulting dust and fragments into the tin dish proceeded to dry blow it.

The modus operandi is as follows: The operator takes the dish about half full of dirt, and standing with his back or side to the wind, if there be any, begins throwing the stuff up and catching it, or sometimes slowly pouring it from one dish to another, the wind in either case carrying away the finer particles. He then proceeds to reduce the quantity by carefully extracting the larger fragments of rock, till eventually he has only a handful or so of moderately fine "dirt" which contains any gold there may be. If in good sized nuggets it is picked out, if in smaller pieces or fine grains the digger slowly blows the sand and dust aside with his breath, leaving the gold exposed. This process is both tedious and unhealthy, and of course can only be carried out with very dry surface dirt. The stuff in which the gold occurred at Mount Brown was composed of broken slate with a few angular fragments of quartz. Yet, strange to say, the gold was invariably waterworn in appearance.

Dry blowing is now much in vogue on the West Australian fields owing to the scarcity of water; but the great objection is first, the large amount of dust the unfortunate dry blower has to carry about his person, and secondly, that the peck of dirt which is supposed to last most men a life time has to be made a continuous meal of every day.

For wet alluvial prospecting the appliances, besides pick and shovel, are puddling tub, tin dish, and cradle; the latter, a man handy with tools can easily make for himself.

In sinking, the digger should be careful to avoid making his shaft inconveniently small, and not to waste his energy by sinking a large "new chum" hole, which usually starts by being about three times too large for the requirements at the surface, but narrows in like a funnel at 10 feet or less. A shaft, say 4 feet by 2 feet 6 inches and sunk plumb, the ends being half rounded, is large enough for all requirements to a considerable depth, though I have seen smart men, when they were in a hurry to reach the drift, get down in a shaft even less in size.

The novice who is trying to follow or to find a deep lead must fully understand that the present bed of the surface river may not, in fact seldom does, indicate the ancient watercourses long since buried either by volcanic or diluvial action, which contain the rich auriferous deposits for which he is seeking; and much judgment and considerable underground exploration are often required to decide on the true course of leads. Only by a careful consideration of all the geological surroundings can an approximate idea be obtained from surface inspection alone; and the whole probable conditions which led to the present contour of the country must be carefully taken into account.

How am I to know the true bottom when I see it? asks the inexperienced digger. Well, nothing but long experience and intelligent observation will prevent mistakes at times, particularly in deep ground; but as a general rule, though it may sound paradoxical, you may know the bottom by the top.

That is, we will assume you are sinking in, say, 10 to 12 feet ground in a gully on the bank of which the country rock is exposed, and is, say, for instance, a clay slate or sandy slate set at a certain angle; then, in all probability, unless there be a distinct fault or change in the country rock between the slate outcrop and your shaft, the bottom will be a similar slate, standing at the same angle; and this will very probably be overlaid by a deposit of pipeclay, formed by the decomposition of the slates.

From the crevices of these slates, sometimes penetrating to a considerable distance, you may get gold, but it is useless attempting to sink through them. If the outcropping strata be a soft calcareous (limy) sandstone or soft felspathic rock, and that be also the true bottom, great care should be exercised or one is apt to sink through the bottom, which may be very loose and decomposed. I have known mistakes made in this way when many feet have been sunk, and driven through what was actually bed rock, though so soft as to deceive even men of experience. The formation, however, must be the guide, and except in some specially difficult cases, a man can soon tell when he is really on bed rock or "bottom."

On an alluvial lead the object of every one is to "get on the gutter," that is, to reach the lowest part of the old underground watercourse, through which for centuries the gold may have been accretionising from the percolation of the mineral-impregnated water; or, when derived from reefs or broken down leaders, the flow of water has acted as a natural sluice wherein the gold is therefore most thickly collected. Sometimes the lead runs for miles and is of considerable width, at others it is irregular, and the gold-bearing "gutter" small and hard to find. In many instances, for reasons not readily apparent, the best gold is not found exactly at the lowest portion of these narrow gutters, but a little way up the sides. This fact should be taken into consideration in prospecting new ground, for many times a claim has been deserted after cleaning up the "bottom," and another man has got far better gold considerably higher up on the sides of the gutter. For shallow alluvial deposits, where a man quickly works out his 30 by 30 feet claim, it may be cheaper at times to "paddock" the whole ground—that is, take all away from surface to bottom, but if he is in wet ground and he has to drive, great care should be taken to properly secure the roof by means of timber. How this may best be done the local circumstances only can decide.

CHAPTER III
LODE OR REEF PROSPECTING

The preceding chapter dealt more especially with prospecting as carried on in alluvial fields. I shall now treat of preliminary mining on lodes or "reefs."

As has already been stated, the likeliest localities for the occurrence of metalliferous deposits are at or near the junction of the older sedimentary formations with the igneous or intrusive rocks, such as granites, diorites, etc. In searching for payable lodes, whether of gold, silver, copper, or even tin in some forms of occurrence, the indications are often very similar. The first prospecting is usually done on the hilltops or ridges, because, owing to denudation by ice or water which have bared the bedrock, the outcrops are there more exposed, and thence the lodes are followed down through the alluvial covered plains, partly by their "strike" or "trend," and sometimes by other indicating evidences, which the practical miner has learned to know.

For instance, a lesson in tracing the lode in a grass covered country was taught me many years ago by an old prospector who had struck good gold in the reef at a point some distance to the east of what had been considered the true course. I asked him why he had opened the ground in that particular place. Said he, "Some folks don't use their eyes. You stand here and look towards that claim on the rise where the reef was last struck. Now, don't you see there is almost a track betwixt here and there where the grass and herbage is more withered than on either side? Why? Well, because the hard quartz lode is close to the surface all the way, and there is no great depth of soil to hold the moisture and make the grass grow."

I have found this simple lesson in practical prospecting of use since. But the strike or course of a quartz reef is more often indicated by outcrops, either of the silica itself or ironstone "blows," as the miners call them, but the term is a misnomer, as it argues the easily disproved igneous theory of veins of ejection, meaning thereby that the quartz with its metalliferous contents was thrown out in a molten state from the interior of the earth. This has in no case occurred, and the theory is an impossible one. True lodes are veins of injection formed by the infiltration of silicated waters carrying the metals also in solution. This water filled the fissures caused either by the cooling of the earth's crust, or formed by sudden upheavals of the igneous rocks.

Sometimes in alluvial ground the trend of the reef will be revealed by a track of quartz fragments, more or less thickly distributed on the surface and through the superincumbent soil. Follow these along, and at some point, if the lode be continuous, a portion of its solid mass will generally be found to protrude and can then again be prospected.

There is no rule as to the trend or strike of lodes, except that a greater number are found taking a northerly and southerly course than one which is easterly and westerly. At all events, such is the case in Australia, but it cannot be said that either has the advantage in being more productive. Some of the richest mines in Australasia have been in lodes running easterly and westerly, while gold, tin, and copper, in great quantity and of high percentage to the ton, have been got in such mines as Mount Morgan, Mount Bischoff, and the Burra, where there are no lodes properly so-called at all.

Mount Morgan is the richest and most productive gold mine in Australasia and amongst the best in the world.

Its yield for 1895 was 128,699 oz. of gold, valued at 528,700 pounds. Dividends paid in 1895, 300,000 pounds.

This mine was opened in 1886. Up to May 31, 1897, the total yield was 1,631,981 ozs. of gold, sold at 6,712,187 pounds, from which 4,400,000 pounds have been paid in dividends. (See Mining Journal, for Oct. 9, 1897.)

Mount Morgan shareholders have, in other words, divided over 43 1/2 tons of standard gold.

The Burra Burra Mine, about 100 miles from Adelaide, in a direction a little to the east of north, was found in 1845 by a shepherd named Pickett. It is singularly situated on bald hills standing 130 feet above the surrounding country. The ores obtained from this copper mine had been chiefly red oxides, very rich blue and green carbonates, including malachite, and also native copper. The discovery of this mine, supporting, as it did at one time, a large population, marked a new era in the history of the colony. The capital invested in it was 12,320 pounds in 5 pound shares, and no subsequent call was ever made upon the shareholders. The total amount paid in dividends was 800,000 pounds. After being worked by the original owners for some years the mine was sold to a new company, but during the last few years it has not been worked, owing in some degree to the low price of copper and also to the fact that the deposit then being worked apparently became exhausted. For many years the average yield was from 10,000 to 13,000 tons of ore, averaging 22 to 23 per cent of copper. It is stated that, during the twenty-nine and a half years in which the mine was worked, the company expended 2,241,167 in general expenses. The output of ore during the same period amounted to 234,648 tons, equal to 51,622 tons of copper. This, at the average price of copper, amounted to a money value of 4,749,224 pounds. The mine stopped working in 1877.

Mount Bischoff, Tasmania, has produced, since the formation of the Company to December 1895, 47,263 tons of tin ore. It is still in full work and likely to be for years to come.

Each of these immense metalliferous deposits was found outcropping on the summit of a hill of comparatively low altitude. There are no true walls nor can the ore be traced away from the hill in lode form. These occurrences are generally held to be due to hydrothermal or geyser action.

Then again lodes are often very erratic in their course. Slides and faults throw them far from their true line, and sometimes the lode is represented by a number of lenticular (double-pointed in section) masses of quartz of greater or less length, either continuing point to point or overlapping, "splicing," as the miners call it. Such formations are very common in West Australia. All this has to be considered and taken into account when tracing the run of stone.

This tyro also must carefully remember that in rough country where the lode strikes across hills and valleys, the line of the cap or outcrop will apparently be very sinuous owing to the rises and depressions of the surface. Many people even now do not understand that true lodes or reefs are portions of rock or material differing from the surrounding and enclosing strata, and continuing down to unknown depths at varying angles. Therefore, if you have a north and south lode outcropping on a hill and crossing an east and west valley, the said lode, underlying east, when you have traced its outcrop to the lowest point in the valley, between the two hills, will be found to be a greater or less distance, according to the angle of its dip or underlie, to the east of the outcrop on the hill where it was first seen. If it be followed up the next hill it will come again to the west, the amount of apparent deviation being regulated by the height of the hills and depth of the valley.

A simple demonstration will make this plain. Take a piece of half-inch pine board, 2 ft. long and 9 in. wide, and imagine this to be a lode; now cut a half circle out of it from the upper edge with a fret saw and lean the board say at an angle of 45 degrees to the left, look along the top edge, which you are to consider as the outcrop on the high ground, the bottom of the cut being the outcrop in the valley, and it will be seen that the lowest portion of the cut is some inches to the right; so it is with the lode, and in rough country very nice judgment is required to trace the true course.

For indications, never pass an ironstone "blow" without examination. Remember the pregnant Cornish saying with regard to mining and the current aphorism, "The iron hat covers the golden head." "Cousin Jack," put it "Iron rides a good horse." The ironstone outcrop may cover a gold, silver, copper or tin lode.

If you are searching for gold, the presence of the royal metal should be apparent on trial with the pestle and mortar; if silver, either by sight in one of its various forms or by assay, blowpipe or otherwise; copper will reveal itself by its peculiar colour, green or blue carbonates, red oxides, or metallic copper. It is an easy metal to prospect for, and its percentage is not difficult to determine approximately. Tin is more difficult to identify, as it varies so greatly in appearance.

Having found your lode and ascertained its course, you want next to ascertain its value. As a rule (and one which it will be well to remember) if you cannot find payable metal, particularly in gold "reef" prospecting, at or near the surface, it is not worth while to sink, unless, of course, you design to strike a shoot of metal which some one has prospected before you. The idea is exploded that auriferous lodes necessarily improve in value with depth. The fact is that the metal in any lode is not, as a rule, equally continuous in any direction, but occurs in shoots dipping at various angles in the length of the lode, in bunches or sometimes in horizontal layers. Nothing but actual exploiting with pick, powder, and brains, particularly brains, will determine this point.

Where there are several parallel lodes and a rich shoot has been found in one and the length of the payable ore ascertained, the neighbouring lodes should be carefully prospected opposite to the rich spot, as often similar valuable deposits will thus be found. Having ascertained that you have, say, a gold reef payable at surface and for a reasonable distance along its course, you next want to ascertain its underlie or dip, and how far the payable gold goes down.

As a general rule in many parts of Australia—though by no means an inflexible rule—a reef running east of north and west of south will underlie east; if west of north and east of south it will go down to the westward and so round the points of the compass till you come to east and west; when if the strike of the lodes in the neighbourhood has come round from north-east to east and west the underlie will be to the south; if the contrary was the case, to the north. It is surprising how often this mode of occurrence will be found to obtain. But I cannot too strongly caution the prospector not to trust to theory but to prove his lode and his metal by following it down on the underlie. "Stick to your gold" is an excellent motto. As a general thing it is only when the lode has been proved by an underlie shaft to water level and explored by driving on its course for a reasonable distance that one need begin to think of vertical shafts and the scientific laying out of the mine.

A first prospecting shaft need not usually be more than 5 ft. by 3 ft. or even 5 ft. by 2 ft. 6 in., particularly in dry country. One may often see in hard country stupid fellows wasting time, labour, and explosives in sinking huge excavations as much as 10 ft. by 8 ft. in solid rock, sometimes following down 6 inches of quartz.

When your shaft is sunk a few feet, you should begin to log up the top for at least 3 ft. or 4 ft., so as to get a tip for your "mullock" and lode stuff. This is done by getting a number of logs, say 6 inches diameter, lay one 7 ft. log on each side of your shaft, cut two notches in it 6 ft. apart opposite the ends of the shaft, lay across it a 5 ft. log similarly notched, so making a frame like a large Oxford picture frame. Continue this by piling one set above another till the desired height is attained, and on the top construct a rough platform and erect your windlass. If you have an iron handle and axle I need not tell you how to set up a windlass, but where timber is scarce you may put together the winding appliance described in the chapter headed "Rules of Thumb."

If you have "struck it rich" you will have the pleasure of seeing your primitive windlass grow to a "whip," a "whim," and eventually to a big powerful engine, with its huge drum and Eiffel tower-like "poppet heads," or "derrick," with their great spindle pulley wheels revolving at dizzy speed high in air.

"How shall I know if I have payable gold so as to save time and trouble in sinking?" says the novice. Truly it is a most important part of the prospector's art, whether he be searching for alluvial or reef gold, stream or lode tin, copper, or other valuable metal.

I presume you know gold when you see it?

If you don't, and the doubtful particle is coarse enough, take a needle and stick the point into the questionable specimen. If gold the steel point will readily prick it; if pyrites or yellow mica the point will glance off or only scratch it.

The great importance of the first prospect from the reef is well shown by the breathless intensity with which the two bearded, bronzed pioneer prospectors in some trackless Australian wild bend over the pan in which the senior "mate" is slowly reducing the sample of powdered lode stuff. How eagerly they examine the last pinch of "black sand" in the corner of the dish. Prosperity and easy times, or poverty and more "hard graft" shall shortly be revealed in the last dexterous turn of the pan. Let us hope it is a "pay prospect."