IMAGE EVALUATION TEST TARGET (MT-3) 1.0 I.I ■^1^ 125 ■ 50 ■' ima |j6 US 2.2 S 1^ iio IL25 llllljy_ ill 1.6 % /a y: y A ,v :<\^ \\ ^ (meaning CONTINUED"), or the symbol y (meaning "END"), whichever applies. Un des symboles suivants apparattra sur la der- nlAre image de cheque microfiche, selon le cas: le symbole — ^ signifie "A SUIVRE", le symbols ▼ signifie "FIN". The original copy was borrowed from, and filmed with, the Itind consent of the following institution: Canadian institute for Scientific and Technical Information, National Research Council Maps or plates too large to be entirely included in one exposure are filmed beginning in the upper left hand corner, left to right and top to bottom, as many frames as required. The following diagrams illustrate the method: L'exemplaire film6 fut reproduit grAce d la g6nArosit6 de l'6tablissement prAteur suivant : Institut Canadian de I'information scientifique et technique, Conseil national des recherches Les cartes ou les planches trop grandes pour Atre reproduites en un seul clichA sont filmAes A partir de I'angle supArieure gauche, de gauche A droite et de haut en has, en prenant le nombre d'images nAcessaire. Le diagramme suivant illustre la mAthode : 1 2 3 1 2 3 4 5 6 PI c I'lC > pra(;ttcal instructions FOR V H K 1),K r K R M I X A '1' 1 () N BY FURNACl-: ASSAY OF GOLD AND SILVER I N ROC KS Ax\ 1) OR KS, UN K. J. CHA1^NL\N, I'u.l)., 1.1,1). 'rofessur of Miiieraloyy and (leology in University Colioge, loioiUu ; ;uirl Ai-ting Prolessor of Mining Geology, Blowpipe Practice, and Assaying, in the l\)ronto School ot" Practical Science. I'O KON TO : COl'l'. CI.AKK .V CO., 9 FRONT STKi:!.'! WK.-^r i88i. AOT1.IV "'» r CHAPMAN'S ASSAY NOTES. INSTRUCTIONS FOR THK I)ETP:RMINATI0N OF (iOFl) AND SILVER IN ROCKS AM) ORES. RV I UK SA\fh: AUTHOR. I. AN OUTLINM-: OF THE GEOLOC.V OK CANADA. H\SKI) ON A SUBDIVISION OF THK PKOVINCKS INTO NATURAL AREAS. /r/M su- sketch-maps and 86 fi^ires of charaderhtir fossils. Thi-, is the only published work which presents a systematic view ot the geology of the entire Dominion. It ha-, been drawn up not to serve simply as a College text-book, but for consultation by goneral readers. II. HLOWl'llM-: PKAC'l'K K. WIIH oRKilNAl. L'ABLES FOR THE UETERMIN A Ih 'N Ol- AI.I. KNOWN MINERALS. rhis work (published in 1880) comprises two distinct parts : An Cnitline of tilowpipe Practice, as applied to the qualitative examma- t,on of inorganic bodies generally ; and a series of Determmatu.- Mineral Tables, with accompanying crystallographic an.l spectn,- .'icopic notes. COPl', Cl.AKK & CO., rORON TO. ADVERTISEMENT. I The following notes contain definite instructions for the examination or assay by furnace operations of all rock-mat- ters and other naturally occurring mineral bodies in which gold or silver is known or suspected to be present. Although given expressly in condensed form, the notes embody various tables and many explanatory directions not given, to the writer's knowledge, in other publications ; whilst, at the same time, they are kept free from sundry complicated de- tails belonging solely to the assay of bullion and other arti- ficial alloys. As they are intended for actual use in the laboratory, it has not been thought necessary to add figures of the balances, furnaces, muffles, scorifiers, tongs, cupel- moulds, and other pieces of apparatus employed in these operations. The student will necessarily see these things for himself ; and he will find their proper form and manipu- lation fully described in the text. School of Practical Science, Toronto, May 30th, 1881. CONTENTS. — • — CHAPTER I. INTRODUCTORY OBSERVATIONS. § 1. Assays in general. Rock and Mineral assays for Gold and Silver " § 2. Gold ores ** § 3. Silver ores ** CHAPTER II. SAMPLING AND PREPARATION OF ASSAY-MATTERS. § 1. Assay-Samples in general • 1^ §2. Preparation of the assay -matter : Implements required . . U CHAPTER III. THE SCORIFICATION PROCESS. § 1. Object and general explanation of the Process 14 § 2, Apparatus -^^ § 3. Reagents • ^^ § 4. Weighing and dressing samples for scorification 18 § 5. Examples of assay-mixtures 20 § 6. Details of the Scorification Process • 24 § 7. Separation and cleaning up of the workable lead or scori- fication-button 25 CHAPTER IV. THE CRUCIBLE PROCESS. § 1. Object and general explanation of the Process 26 § 2. Apparatus 27 § 3. Reagents ^^ 11 CONTENTS. § 4. Roasting 32 § 5. Weighing and dressing samples for crucible assay 33 § 6. Furnace manipulation 35 § 7 Manipulation of the Crucible Button 36 CHAPTER V. CUPELLATION. § 1. Object and essential character of Cupellation 37 § 2. Apparatus and api^liances . 38 § 3. Preparation of Cupels 40 § 4. Details of the Cupellation Process 43 CHAPTER VI. ESTIMATION OF GOLD AND SILVER IN CUPEL BUTTONS. § 1. Explanatory Remarks on the Separation of Gold and Silver 48 § 2. Apparatus 50 § 3. Reagents 52 § 4. Details of the Process 52 CHAPTER VII. ASSAY TABLES. Table I. Assay-weight, 5 grammes 57 Table II. Assay-weight, 25 grammes 5^ Table III. Assay-weight, 50 grammes 59 Table IV. Assay- weight, 29*17 grammes CO Table V. Assay- weight, 32 67 grammes 60 Table VI. Assay-weight, 1 oz 61 Table VII. Percentage Values 62 Table VIII. Average value of Gold 63 Table IX. Approximate Sp. Gr. of Gold Alloys 63 I *• FURNACE ASSAYS OP GOLD AND SILVER ORES. CHAPTER I. Introductory Observations, [Nature of Assays. Enumeration of Processes. Ores.] O Gold and § 1. Assays in general. Rock and Mineral Assays for Gold and Silver : — Assaying is strictly a bnmcli of quanti- tative chemical analysis, diiftjring from the latter, properly so-called, by determining only those components of a sub- stance which impart to it a commercial value. In some cases, the assay is ])erformed by furnace operations ; in others, by solution and precipitation, &c., as in ordinary chemical analysis ; and in others, again, by volumetric methods. The present Notes refer solely to furnace assays of mineral matters containing, or suspected to contain, gold or silver.* These assays, as regards their modus operandi, are of two general kinds : Scorification * Mining Assays of this description are quite distinct, it must be understo(,d, from Mint or jeweller's assays, in which bullion and metallic alloys containing gold and silver alone come under examination. The assays to which the pre- sent publication refers are not gold and silver assays, properly so-called, but assays of rocks,vin6stones, and mineral ores generally, for the detection and determination of any gold or silver that may be present in these matters. 8 FURNACE ASSAYS. Aasays, applied to comparatively rich ores; and Crucible Assays, adopted essentially in the examination of poor ores. In both, however, the preparatory stages (including the sampling and preparation of the assay-matter) are alike ; and both terminate in the common process of Cupellation. In the scorification assay a small portion, only, of the prepared ore is directly operated on ; whilst in the crucible assay a much larger portion of the ore can be taken. In all cases, at least a couple of assays should be made simultaneously.* The complete assay comprises the following processes : (1) Sampling and Preparation of the Assay-matter (Chapter II.) ! Scorification (Chapter III.), or Crucible Treatment (Chapter IV.) (3) Cupellation (Chapter V.) (4) Treatment of the Cupel-Button (Chapter VI.) * Objections are often ignorantly urged against laboratory assays, as being made on portions of matter too small to give trustworthy results regarding the quality of the vein or other deposit to which the assays refer ; but if the samples be properly taken (as directed in Chapter II), assays of even a few grammes of matter (forming in most cases, it must be remembered, portions of samples weighing several pounds) may be thoroughly relied on as regards the general cliaracter of the deposit— i. e., its comparative richness or poverty — although this may of course vary at different depths. Very frequently an assay of this kind serves to reveal the absolute barrenness of deposits from which large returns are falsely stated to have been obtained ; and much subsequent loss and disappointment is thus prevented. In preliminary mining operations, again, small assays are especially useful ; and when the ore is not of an ex- ceedingly variable character their results are quite as trustworthy as those derived from the treatment of large quantities of the deposit. This wiU apply especially to argentiferous lead-ores and auriferous pyrites. Assays, also, are indispensable in checking the results of furnace operations on the large scale ; and in the purchase and sale of ores generally. ^ [« GOLD AKD SILVER OllES. § 2. Gold Ores : — The metal gold occurs in Nature chiefly under the following conditions: (1) as ''free gold " (i. e., in a simple, uncombined state, although com- monly alloyed with a little silver) disseminated either in small nuggets or in more or less imperceptible particles through quartz or other solid rock-matter; (2) in the same condition in river-sands and gravels or other alluvial matters forming the "jjlacer digginrjs,'' &c., of Western explorers, the " Sei/enlager" of Germsin miners; (3) in probably the metallic state (or as an arsenide or sulphide?) in some examples of mispickel, iron pyrites, copper pyrites, blende and other similar ores, in which it is present in very minute quantity as an " accidental component;" and (4), in some rare tellurides. Assay- samples consist very generally of pieces of quartzose gangue or veinstone, carrying interspersed particles of pyrites, mispickel, zinc-blende, galena, &c., without any visible show of gold. § 3. Silver Ores: — These are somewhat numerous. The principal comprise: (1) Native silver (usually in small grains or scales, or in leafy or filiform examples) in • assay-matter, with pure lead (from which these metals are afterwards separated by cupellation, Chapter Y.); whilst iron, arsenic, sulphur, intermixed rock-matter, &c,, become "scorified" or pass into slag. The process is performed in small, thick, saucer-shaped vessels of fire- clay, known as " scorifiers." These are strongly heated in a muffle or thin fireclay oven according to the method described in detail under § 5, below, and the "workable lead" is then poured into an iron or copper mould, previously warmed to prevent the lead from spitting or throwing off small portions of its mass. The lead button thus obtained, is squared up and cleaned from adherent slag on the anvil, after which it is cupelled as described in Chapter V. § 2. Apparatus : — The following pieces of apparatus are needed in preparing the assay-mixture and carrying out the process of scorification. ( 1 ) An ordinary chemical- balance, with gramme weights ranging from fifty ■ SCOIIIFICATION APPAllATL'S. 15 ^ . grammes downwards. f (2) A porcelain capsule or crucible to liold the weighed matter, and a tare for these vessels. The tare may consist of a thin brass box with sere wed-on top, holding a few particles of test-lead or some fine shot. (3) A small copper-scoop, or two, for taking up the powdered ore, test-lead, (fee, and a small spatula for mixing the assay-matters. (4) A fixed or portable muflle-furnace. For ordinary work, a small portable furnace is amply sufficient. The square fire- clay furnaces, bound with sheet-iron bands, made at the Battersea Works (London, England,) are especially serviceal)le. The cracks, which commonly occur in them when they are first lighted, are of no consequence. A convenient size is that denoted by the letter C, stamped on the moveable doors and other pieces of the furnace. This size takes a muffle 8 inches long by 4J inches broad. The small "Luhme furnaces," made of sheet-iron thickly lined with fire-clay, are also very useful ; but the fire-clay lining will require to be patched or replaced pretty constantly if the furnace be in active use. Repairs are effected by kneading some good fire- clay with a very small quantity of water into a stiff* paste, and pressing this strongly into the damaged places by a trowel, the surface being properly smoothed over after- wards. The patchings must be left to dry thoroughly t A very expensive balance is not required in these preliminary assaying processes, but for weighing the cupellation buttons and the fine gold separated from the latter, a delicate assay-balance is, of course, essential (see Cliapter VI.). For crucible operations it is convenient to have certain special weight s , as described under the crucible process in Chapter IV. w 16 FURNACE ASSAYS. for several days before the furnace is again used.* The fuel for these furnaces consists of charcoal chopped by a small light hatchet into blocks of about two inches square. Large pieces do not fall properly, and dust destroys the draught. (5) A fire-clay muffle of suitable dimensions to fit the furnace. Formerly, these muffles had always slits or air-jmssages at the sides and back, but they are now generally made without am, and are consequently stronger. Under both forms, however, they are easily broken. Duplicates should, therefore, be kept at liand.t It is advisabe to spread a little boneash thinly over their floor to prevent the scorifiers from adhering in case some of the contents of the latter should be allowed by mismanagement to overflow, or should escape through the cracking of a faulty scorifier. (6) An assortment of fire-clay scorifiers. Those turned out by the Battersea Works are of excellent quality. The * Fur private laboratories, or occasional use, the small gas-furnaces maJe by Fletcher and others, if properly handled, are also very serviceable. t Fire-clay muflfles, in remote places, cannot always be procured. The writer has thus been compelled at times to use cast iron muffles. In these, a slit at the back can of course be made in the casting ; but if holes at the side be re- quired, they must be bored subsequently. Muffles of this kind answer well enough in small furnaces ; and, as a rule, they will serve for thirty or forty assays before becoming too much corroded for additional use. In wind-fur- naces, however, or where the draught is very strong, they are rapidly melted and destroyed. Wrought iron muffles, made in two pieces, answer better. In these, the floor has a slight flange turned up on each side, and the dome con- sists of a separate piece, bent into the form of an arch and kept by the flanges in its place. The back is entirely open, but it can of course be closed or par- tially closed by a piece of fire-brick roughly cut into shape. A large cruciblet | laid on its side, may sometimes serve as a makeshift muffle where nothing else is at hand. In the small gas-furnaces, plumbago mufflss are commonly used. SCORIFICATION APPARATUS. 17 more generally useful sizes measure two inches, and an inch-and-three-quarters, respectively, across the top. (7) A pair of tongs, about two feet in length, with spring blades flattened and somewhat enlarged at the ends, for feeding the furnace with charcoal. These are commonly known as furnace-tongs or charcoal-tongs. (8) A pair of scorifier-tongs for placing the scorifiers in the muffle, and for removing them from the latter, after scorifica- tion, and pouring their contents into the assay-mould described below. These tongs have flat spring blades of about three feet in length. One is the under and the other the upper blade. The under blade is fashioned into a kind of fork or horseshoe-shaped expansion to fit the bottom of the scorifier. The upper blade is of one width throughout. When in use it goes across the flat top of the scorifier, and as the base of the latter rests within the horseshoe of the lower blade, the scorifier is held very securely, both when placed in the muffle and when removed and reversed over the assay-mould. (9) A thick slab of iron or copper, with two (or several) saucer- shaped depressions on one of its flat surfaces, and a metal handle (with wooden " grasp ") strongly screwed into one end. This is the assay-mould for the reception of the "workable lead" from the scorifier. The bottom of the saucer-shaped receptacles must be rubbed lightly with chalk or red ochre to prevent the lead from adhering, and the entire mould must be warmed strongly imme- diately before use. This is best effected by placing it for a few minutes on the ledge before the muffle door, or on tS FURNACE ASSAYS. the outside of the furnace at the top. (10) An anvil or block of hard steel from four to six inches square and of about the same thickness, with a tongue or projection several inches in length at the under side for insertion into a block of hard wood. The latter may consist of part of a tree-trunk eight or nine inches or a foot in diameter and about 2J or 3 feet high. It should be perfectly level at the base so as to stand firmly and securely. A good hammer, with head of about 1 lb. or 1^ lb. in weight, should accompany the anvil, and be hung up (between a couple of nails supporting the head) on the adjacent wall. One end of the hammer-head must be chisel-shaped, the other end flat and square. § 3. Reagents : — The reagents required in the scorifica- tion -process comprise merely granulated lead (commonly known as " test-lead "), dried borax, and (for occasional use) a little charcoal powder. Every sample of lead purchased for the laboratory should be tested by cupella- tion before actual use, to ensure the absence of silver. See Chapter V. § 4. Weighing and Dressing of Samples for Scorif ca- tion: — The sieved and thoroughly mixed powder {§2, Chapter II.) is poured from its receptacle on to a sheet of paper and is made up into a conical heap. This is divided roughly by a spatula into quarters, and from each quarter small portions are taken and placed in the weighing capsule until 5 grammes are thus weighed out for assay. This amount is placed in a scorifier, and is '' 8C0RIFICATI0N MIXTUUES. 191 dressed with its proper amount of granuliitc 1 kfud, vary- ing from about 20 to over 50 grammes, accoi-dincf to the nature of the substance, as shewn in the Tables of Assay mixtures under § 5, below. About one-third, or rather more, of the lead, is mixed in the scoritier with the powdere^ FURNACE ASSAYS. If turninij with a milligramme when loaded with the above weight, it will ho sufHciently delicate for criicil)lo and hco- rification weighings, but a projx'r assay-balance indicating tlie tenth of a niilligranime is necessary for the estimation of th(; final cuiK'llation-products (see Chapter VI). {'2) A porcelain capsule (and tare) to hold the assay-matter whilst being weighed. ('>]) A co[)per scoop with flat floor and raised edge, provided with a short wooden handle. This S(irvcs for mixing the assay-matter with lithai'ge and llux, and [)Ouring it into the crucible. It may be about '^ inches long and 4 inches wide at the upper end, taper- ing to about H- inch at the point. (-I-) A light steel spatula with wooden handle, for mixing the assay matters in the copper scoop. (5) A melting or fusion furnace. The portable furnaces of sheet-iron thickly lined with lire-clay, made by Luhme, of Berlin, answer perfectly; or, in place of these, the fire-clay, iron-bound, melting furnaces of the Battersea Company may be used. As regards size, those with a diameter of 8 or 9 inches and a depth of about dh inches will be found most convenient. The domed top with its short chimney is removable. When this is taken off in order to remove the pots, after the fusion of the assay, it must be phiced on a brick floor or on the broad sandbath which accompanies the jjuhme furnaces. The method of fixing the crucibles and igniting the furnace is described in § 6 of this Chapter. I The pro})er fuel is good charcoal in pieces of about two inches square ; but a few larger pieces to put over the pots should also be at hand. (6) A supply of fire-clay { CnUCIBLE PROCESS. APPARATUS. 29 • crucibles or " pots." Those of the B.attersca Works can^ not bo surpassed. The rouuvl pattern, 4 indies high, .'i inches diameter at top, and 1| inch at bottom, is most suitable. A good stock of this size should be provided, as each assay (if made, as it should be, in duplicate) entails the sacrifice of two crucibles. It is also desirable to have at hand a few pots of larger and some of smaller size, but very large and very small crucibles are com- paratively useless. (7) A few crucible sui)ports. These are small circular blocks of fire-clay, 2 inches in diameter and 1 -1 inch high. In their absence, a squared piece of of fire-clay brick, or a stout scorifier (reversed), may be used. If the crucibles are placed directly on the furnace bars, they are liable to adhere to these ; and the heat is greater an inch or two above the grate than immediately upon it. (8) A pair of crucible tongs, scissor-shaped, about two feet long with the ends of the blades fiattened inside and bent slightly downwards. A pair of elastic tongs for feeding the furnace with charcoal (see Chapter IV., § 2 [7]) are also necessary. (9) An iron pan, such as a small cast-iron frying-pan, to hold under the hot crucible when this is removed from the furnace, as described in § 6 of this Chapter. (10) A small supply of fire-clay roasting-dishes, about three inches in diameter. These, of course, require a muffle-furnace, but they are used only in special cases (see § 5). The flat-based dishes are more conveniently handled than those of watch-glass form, but the latter are more durable. Tlio inside is nibbed or smeared with chalk, red ochre, oi- plumbago, 30 FURNACE ASSAYS. before use. (II) A piece of stout iron wire ten or twelve inches loii«^ (slig'itly flattened at one extremity, and inserted at the otiiei- into a wooden handle) to serve as a stirrer during the roasting process. (12) An anvil, on a solid block of wood, and .a good hammer of about a pound in weight at the heail, with one end square and the other chisel-shaped. Thtise are described in Chapter IV., §2 (10). They are used for breaking the crucible and extracting and sqiiaring up the workable lead-button, as as described in § 5 of the present Chapter. § 3. Reagents : — In the examination of rock-matters for gold and silver by crucible assay, but few reagents are required. These com[)rise, essentially: (1) Litharge; (2) Fluxing materials ; (3) Covering materials. (1) X{itate will be produced if hydrochloric acid be present. (2) A solution of common salt (NaCl), or some hydrochloric acid, for re-obtaining the silver of the cupel-button (if this be desired) from the nitric acid solution. (3) A piece or two of pure lead foil, and some finely-sifted boneash, for re-cupelling the gold buttons when necessary, (4) A small strip of pure silver. This may be obtained from an ordinary silver-coin by separating the copper alloy ! either by fusion with lead and subsequent cupellation, or by solution of the coin in nitric acid and precipitation of the silver as chloride, the latter, after thorough wash- ing, being fused with some reducing flux in a porcelain crucible, and the reduced silver hammered out for use. § 4. Detailed Treatment of the Cupel-button : — The small button or globule, after being carefully separated from the cupel, and cleaned from adhering matter, as explained at the close of Chapter V., is taken in a little porcelain capsule to tlie balance room, and its weight ia TREATMENT OF CUPEL BUTTON. 53 very accurately ascertained. The button is then replaced in the capsule, and some pure nitric acid diluted with about an equal bulk ot* water is dropped upon it, and the capsule is held for a few minutes, or until the acid begins to boil, over the flame of a spirit-lamp or Bunsen-burner. One of three results will then ensue : (i) the globule will dissolve wholly ; or (u) it will dissolve in part only, the gold separating as a dark-brown or black powder ; or (Hi) it will merely become black on* the surface, and in this latter case scarcely any orange-brown fumes will be evolved from the acid, whilst copious fumes of this kind will be given off if the button be dissolved in part or wholly. If the solution be complete, so that nothing remain undissolved, the button will have consisted entirely of silver. Its corresponding value per ton of ore may therefore at once be calculated or otherwise determined by reference to the proper table in Chapter VII. If the button be in part dissolved, with separation of brown flakes or powder, the liquid must be carefully decanted from the capsule, and the operation repeated with undiluted acid. The dark powder is then washed two or three times with distilled water, this being decanted cautiously after each washing. As the powder is very heavy, the washing is easily efiected without risk of loss. The last remains of the water are drawn off" by «, fold of filtering or blotting paper, or are expelled by •cautiously warming the capsule. The dry powder is then shaken or swept by a camers-hair pencil into one of 54 FURNACE ASSAY'S. the little weighing capsules of the assay-balance, and its weight, to the tenth of a milligramme, is carefully ascertained. If desired, it can be folded afterwards in a piece of lead foil, and melted and cupelled in one opera- tion by the blow-pipe, and the resulting gold globule can be preserved in a short piece of glass tube closed at each end by a piece of cork. Or, to show its true nature, the dark powder may be compressed strongly by a glass stirring-rod, or rubbed in an agate mortar, when it will quickly assume the yellow colour and metallic lustre of ordinary gold. The weight of the silver is, of course, obtained "by difference," i.e., by deducting the weight of the gold from that of the cupel-button. When, on the other hand, the cupel-button merely becomes darkened on the surface by treatment with nitric acid (as in all buttons which show a rich gold colour) the process known as "quartation" must be resorted to for the purpose of extracting the silver, so as to obtain the true weight of the gold in the button. It is commonly assumed that unles the silver be to the gold in the proportion of 3 to 1, the gold prevents the acid from thoroughly dissolving it. Complete solution of the silver is effected, however, when the proportions are as 2 (or even 1|) to 1. In the case of very rich buttons, therefore, a small cutting of silver three or four times at least, the size of the button, must be placed with the latter, in contact with a piece of lead foil, on a blowpipe Cupel, and the whole fused together and then subjected to cupellation on the same support. The weight of the ASSAY TABLES. 55 added silver need not, of course, be taken. The resulting silver-gold globule will be quite white, and all the silver will be readily extracted from it by treatment with nitric acid, as directed above. The weight of the gold deducted from that of the original cupel-button gives, of course, the weight of the silver present in the assay- matter. In some exceptional cases the auriferous button left on the cupel may be too large to be subjected to blowpipe treatment. A button of this kind must be wrapped with a cutting of silver in a })iece of lead foil, and cupelled in the muflfle. Finally, the amount of gold and silver in the assay- matter being thus obtained, the corresponding amount in the ton of ore must be determined — the portion of ore taken for assay being assumed to represent the ore gener- ally. The determination is, of course, very simple. If X grammes (the assay amount) represent the ton of 2000 lbs. or 2240 lbs. of ore — how many ounces, penny- weights, and grains, Troy, will x milligrammes (the amount of gold or silver obtained in the assay) represent 1 The Tables given in the ensuing Chapter will show the required result, in ordinary cases, without calculation. CHAPTER VII. Assay Tables. Table I., of the following series, will be found useful in calculating the ton values of returns obtained from SfS FURNACE ASSAYS. Scorification Assays. Tables II. to V., inclusive, apply to Crucible Assays. Table VI., which also applies to Crucible Assays, is calculated for grain weights. Table VII. shows the ton values corresponding to percentages from 1 to 0-0001. These Tables have been drawn up expressly for the present work. Table IX. does not per- haps belong properly to the series, but may be found useful in certain cases. It is the result of repeated determinations in the writer's laboratory. The following example will serve to explain the Tables generally : — Five grammes of a given ore are scorified with the proper quantity of lead, &c. (see Chapter III.), and the lead-button, thus obtained, yields a cupel-button which weighs 8 milligrammes. This leaves 2 3 milli- grammes of gold after treatment with nitric acid (see Chapter VI. ). The amount of silver in the button was consequently equal to 5-7 milligrammes. Hence (see Table I.) the gold is equivalent to 13oz. 8dwts. 8gr. (= lloz. ]3dwts, Bgrs. + loz. ISdwts. Ogrs.) per ton of 2000 lbs. of ore ; and to 15oz. Odwts. ISgrs. ( = 13oz. Idwt. 8grs. + loz. 19dwts. 5grs.) per ton of 2240 lbs. The silver, in like manner, is shown by the Table to correspond to 33oz. 4dwts. 14grs., and to 37oz. 4dwts. 20grs., per short and long ton, respectively. As already stated, gold and silver ounces are invariably understood to be Troy ounces. ASSAY TABLES. 57 TABLE I. 5 Grammes taken for Assay. Milligrammes of TON of 2000 Lbs. Ton or 2240 Lbs. Gold or Silver Obtained. Oz. Dwts. Grs. Oz. Dwts. Grs. 1 10 58 6 16 65 6 16 9 52 10 58 16 i 8 46 13 8 52 5 ' 8 7 40 16 16 45 14 ! 16 6 35 38 16 ' 6 29 3 8 32 13 8 4 23 6 16 26 2 16 3 17 10 (» 19 8 1 2 11 13 8 13 1 8 ! 1 5 16 16 6 10 16 0.9 5 5 5 17 14 0.8 4 13 8 5 4 13 0.7 4 1 16 4 11 12 ' 0.6 3 10 3 18 10 0.6 2 18 8 3 5 8 0.4 2 6 16 2 12 16 0.3 1 15 1 19 5 0.2 1 3 8 1 6 3 0.1 11 16 13 n •58 FURNACE ASSAYS. TABLE II. 25 Grammes taken for Assay. MlIXiailAMMEa OF Ton OF 2000 Lbs. Ton OF 2240 Lbs. Gold or Silver Obtained. Oz. Dwts. Grs. Oz. Dwt8. Grs. 10 11 13 8 13 1 8 9 10 10 11 15 4 8 9 6 16 10 9 2 7 8 3 8 9 2 22 6 7 7 16 19 6 5 16 16 6 10 16 4 4 13 8 5 4 12 3 3 10 3 18 10 2 2 6 16 2 12 6 1 1 3 8 1 6 3 0.9 1 1 1 3 12 0.8 18 16 1 21 0.7 16 8 18 17 0.6 14 15 16 0.5 11 16 13 2 0.4 9 8 10 11 0.3 7 7 20 0.2 4 16 5 5i 0.1 2 8 2 14| ASSAY TABLES. TABLE III. 50 Grammes taken for Assay. 59 MlLLIORAMMKS OF Ton OF 2000 Lbs. Ton OF 2240 Lbs. Gold or Silver Obtained. I Oz. Dwts. Grs. Oz. Dwts. Gra. 10 5 16 16 10 , 1 16 !! 9 5 5 1 5 17 14 ! 8 4 13 1 ' 8 1 5 4 13 ' 7 4 1 16 4 11 12 j 6 3 10 3 18 10 6 2 18 8 3 5 8 16 ! 4 • 2 6 16 2 12 3 1 15 1 19 5 1 2 1 3 8 1 6 3 i 1 11 16 13 1 2 0.9 10 2 11 18 0.8 9 8 10 11 0.7 8 4 9 3i 0.6 7 7 20 0.5 6 20 6 13 i 04 4 16 5 5i 0.3 3 12 3 22 0.2 2 8 2 141 0.1 1 4 1 n eo FURNACE ASSAYS. TABLE IV. 29.17 Grammes taken for Assay. Assay-Result IN Gold or Silver. 1 milligramme. 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.05 Tom of 2000 Lbs. Oz. Dwts. 18 16 14 12 10 8 6 4 2 1 TABLE V. 32.67 Grammes taken for Assay. Assay-Result IN Gold or Silver. 1 milligramme. 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.05 Ton of 2240 Lbs. Oz. Dwts. 18 16 14 12 10 8 6 4 2 1 Grs. Grs. J A-SSAY TABLES. 61 TABLE VI. 1 Oz. Avoirdupois taken for Assay. ^ Assay-Rksult Ton OF 2000 Lbs. Ton OF 2240 Lbs. IN Gold on Silver. 02. Dwts. Grs. Oz. 1 Dwts. Org. 1 grain. 66 13 8 74 13 8 0.9 60 67 4 0.8 53 6 16 69 14 16 0.7 46 13 8 52 5 8 0.6 40 44 16 0.5 33 3 16 37 6 16 0.4 26 13 8 29 17 8 0.3 20 22 8 0.2 13 6 16 14 18 6 0.1 6 13 8 7 9 8 0.09 6 6 14 8 0.08 5 6 16 5 19 10 0.07 4 13 8 6 4 13 0.06 4 4 9 13 0.06 3 6 16 3 14 15 0.04 2 13 8 2 19 17 0.03 2 2 4 m 0.02 1 6 16 1 9 21 0.01 13 8 14 22i 62 FURNACE ASSAYS. TABLE VII. A Table of Percentages and Corresponding values per Ton. Percentage. Ton of 2000 Lbs. Ton OF 2240 Lbs. Oz. Dwts. Grs. Oz. Dwts. Grs. 1 291 13 8 326 13 8 0.9 262 10 294 0.8 233 6 16 261 6 16 0.7 204 3 8 228 13 8 0.6 175 196 0.5 145 16 16 163 6 16 0.4 116 13 8 130 13 8 0.3 87 10 98 0.2 58 6 16 65 6 16 0.1 29 3 8 32 13 8 0.09 26 5 29 8 0.08 23 6 16 36 2 16 0.07 20 8 8 22 17 8 0.06 17 10 19 12 0.05 14 11 16 16 6 16 0.04 11 13 8 13 1 8 0.03 8 15 9 16 0.02 5 16 16 6 10 16 0.0) 2 18 8 3 5 8 0.009 2 12 12 2 18 19 0.008 2 6 16 2 12 6 0.007 2 20 2 5 17 0.006 1 15 1 19 5 ' 0.005 1 9 4 1 12 15 i 0.004 1 3 8 1 6 3 ! 0.003 17 12 19 4 0.002 11 16 13 2 O.OOl 5 20 6 13 O.O0O9 5 6 5 21 0.0008 4 16 6 5 0.0007 4 2 4 14 0.0006 3 12 3 22 0.0005 2 22 3 6 0.0004 2 8 2 15 0.0003 1 18 1 23 0.0002 1 4 1 7 0.0001 14 15 J i twrr^Bwr^^i'^^w^^Ffw ASSAY TABLES. 63 TABLE VIII. Average Value of Gold per oz., Troy. Fineness in • Carats. £ .s. d. 24 20. G5 4 5 22 18.93 3 17 11 20 17.21 3 10 10 18 15 49 3 3 9 16 13.77 2 10 8 14 12.05 2 9 7 12 10.32 2 2 6 Note —The value of silver is subject at present to constant fluctuation. The average Bar or Standard Silver wi)l jtiobably oscillate for some time at a few cents over $1 per oz. Troy. Standard Silver consists of 92 5 % pure silver, and 7"6 % copper alloy. Cupelled or Cake Silver will average about a twelfth more in value. TABLE IX. Approximate Sp. Gr. of Gold Alloys. i 1 Fineness in Alloy 1 Carats. Sp. Qr. Gold, %. ((JU-AG) %. 23 18-56 1)5-83 417 22 17-74 91 07 8-33 21 17-22 87-50 12-50 20 16-00 83 34 10 00 19 16-00 79-17 20-83 ! 18 15-42 75-00 25-00 17 14-92 70-83 29-17 16 14-48 06 07 33-33 15 14 00 02-50 37-50 14 13 05 ' 58-33 4167 13 13 28 5417 45 83 12 12-91 50 00 50 '00 INDEX. •■ Acid gangues, 31. Antimoniiil ores, 9, 22. Anvil, 18. Apparatus, 11, 14, 18, 27-30, 38-40, 50-52. Argentiferous galena, 10, 23, 34. Arsenical pyrites, 9, 22. Assays in general, 7-8. Assay Balance, 50. Assay Matters, Preparation of, 11. Assay Mixtures, 20-23. Assay Moulds, 17. Assay Samples, 10. Assay Tables, 55-G3. Assay Tongs, 17, 29, 40. "Astonishing." how effected, 12. Auriferous pyrites, 9, 21. Balances, 14, 15, 27, 50. Basic gangues, 20, 31. Blendiferous ores, 22. Blowpipe Cupellation, 50, 54. Boneash, 39. Borax, 18, 20, 31. Capsules, porcelain, 51. Carat values, 49, 63. Chalk, 17. Chapman's crucible flux, 31. Charcoal, 16. Charcoal tongs, 17, 29. Coup de grace stage in scori- fication, 25. Cover (salt), 31-32. Crucibles, 29. Crucible buttons, 36. Crucible process, 26-37. Crucible supports, 29. Crucible tongs, 29. Cupellation, 37-48. Cupellation loss, 47. Cupels, preparation of, 40. Cupel buttons, 46, 47, 49, 52. Cupel moulds, 39. Cujjel tongs, 40. Cupreous ores, 21, 23. Dressing Samples : For crucible fusion, 33. For scorification, 18. Fluxes, 31. Freezing, 43. Furnace (melting), 28. Furnace (muffle), 15, 38. Furnace tongs, 17, 29, 40. Galena, 10, 23, 34. Gangues, acid, 31. (iangues, basic, 20, 31. Gangues, silicious, 31. Gold, Separation of, from silver, 49, 53-55. Gold alloys, 63. Gold ores, 9. Gold, powder, 53. Gold values, 63. Gramme weights, 14, 27, 61. Hammer, 12, 18, 30. Hydrochloric acid, 52. Iron mortars, 13. Jewellers' gold, 49. €6 INDEX. L-ead buttons, 25-20, 37, 43. Lead foil, 52. Load, granulated, 18. Lead, test, 18. Lead, workable, 25, 37. Litharge, 30. Luhme's furnaces, 15, 28. Mallet, 40. Melting furnace, 28. Mortars, iron, 13. Mortars, porcelain, 40. Muffles, 10, 38. Muffle furnace, 15, 38. Native gold, 9, 23. Native silver, 9, 23. Nickeliferous ores, 20, 22, 45 Nitre, 35. Nitric acid, 52. Parting flasks, 51. Percentages, Table of, 62. Porcelain capsules, 51. Porcelain mortar, 40. Potash, nitiate, 35. Potash, tartrate, 31. Pyrites, 9, 21. Pyritous galena, 23. Pyritous ores, 21, 22. Quartatior, 54. Quartz, 9. Quartzose gangues, 20, 21. Red ochre, 32. Riders, 50, 5i. Roasting dishes, 29. Roasting process, 32. Salt, for coveis, 31, 32. Salt solution, 52. Sampling (»res, 10, 11. Scoops, copper, 28. Scoops, i)orcelain, 31. Scorilication process, 14-26. Scoritiers, 16. Scoriiicr mould, 17. Scorilier tongs, 17. Sieves, 13. Siliceous gangues, 31. Silver, native, 9, 23. Silver ores, 9. Silver, Separation of, from gold, 48, 53-55. Special weights, 27. Specific gravity of gold alloys, 03. Stirrer, 30. Sugar, 31. Supports, crucible, 29. Tartrate of potash, 31. Test-lead, 18. Tongs : assay, 17. charcoal, 17. crucible, 29. cupel, 40. furnace, 17. scissor, 29. scorifier, 17. Weights : for crucible assays, 27, 33. for scorification assays, 18. 19, 21-23. Zinc-holding ores, 22. COPP, CLAKK & CO , PRINTERS, COLBORNE STREET, TORONTO. 32. 1. 14-26. f, from Id alloys. 27, 33. lays, 18, _Sl. ""-— '•'■^■'' '"