Charles George Warnford Lock.

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extracted by lixiviation. If much iron remains with the nickel, the
lixiviated material is dried, mixed with a little pyrite (or other
snlphiir oomponnH) and pand, and fused in a reverberatory furnace so
as to slag off the iron and leave almost pure nickel sulphide, which is
then converted into uxide by calcination.

(6)* The matte, having' been roasted, is treated repeatedly with
hydrochloric or dilute sulphuric acid, to dissolve the nickel and
copper, and cobalt, lead and bismuth, if present. Any iron that may
have gone into solution is precipitated by lime, having previously
been converted into ferric oxide by the addition of lime chloride.
The temperature of the solution is then raised to 158° F., and the
copper is precipitated by calcium carbonate, milk of lime, or a solution
of soda. When all the copper has been thrown down, the cobalt is
precipitated by the careful addition of a solution of calcium chloride
to the perfectly neutral, hot, and not too dilute filtrate. The nickel
is finally precipitated as hydrate by calcium carbonate, milk of hme
or soda. The nickel hydrate is filtered off, dried, heated with sodium
earbonate to decompose any calcium sulphate that may be present,
-washed with acidulated water, dried again, and finally reduced by
carbonaceous materials to the metallic state. This process, being
dependent upon the fractional precipitation of the several metals in
the ore with the same reagents, is subject to slight alterations of
procedure in various works.

The {^reparation of gamierite for the market is of the simplest
description. The crude ore having been reduced by spalling to a
snitable size, a portion consisting of mixed ore and rock is separated
by cobbing, the cobbed ore being always of high grade. The remaiiv-
ing portion, consisting of the fine ore, a good deal mixed with stone,
is all carefully collected and screened in hand sieves of ^| in. holes ;
the fine which passes through is not further treated ; the coarse which
remains in the sieve is hand-picked, the useless stone being rejected.
The picked ore is next mixed with the fines and cobbings. The
crashed mineral has a sp. gr. of only 3, which is so near that of the
serpentine gangue that wet concentration is impossible. If the
cobbed and hand-selected portions only were utilised as a marketable
product, the percentage of the ore would be something like doubled ;
but the crude smaUs which form the bulk of the ore, and which do
not admit of concentration at all, are mixed with the richer portions,
and thus the percentage of the metal is reduced to the average of
about 7-8. In this state it is shipped to Europe. U'he further treat-
ment consists in smelting in a low-blast furnace with coke and
gypsum (or alkali waste or salt-cake), to remove silica, magnesia, <fec.,
as a slag, and produce an iron-nickel regulus. This latter is then
subjected, in a reverberatory furnace, to a series of alternate roastings
and fusions with sand, whereby the iron is gradually slagged ot!', and
almost pure nickel sulphide is iinally obtained ; this may be converted
into oxide by calcination. -Sometimes the first roasting and fusion of
the blast-furnace matte is replaced by bessemerising.
• W. R. Ingalla, En. oud Min. Jl.

2 p 2

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58o ECONOMIC MINING.

The bulk of the Canadian matte is treated by the Oiford Copper
Co^ by the following* method: — The metals in the matte aw
reduced by a preliminary treatment, either by the Bessemer prooen
or by ordinary calcining and melting in a blast-fdmaoe, to a point
where the metals are present substantially as subsulphides. Thii
matte is then melted with an alkaline sulphide (in praoiice with nli-
cake, i. e. sulphate of soda, which in the blast-fumaoe is reduced to
soda sulphide), and a reaction follows in which the copper and irro
take the sulpnur from the soda. By adding the proper proportion d
salt-cake, the bulk of the iron and copper are converted into sulphide,
and mixing with the soda, make a very fluid mass, from whidi tb«
nickel subsulphide separates by gravity, and, on cooling, leaves in
the tope the bulk of the copper and iron and the soda, and in tk
bottoms the bulk of the nickel. On exposure to the weather, the
soda in the tops is converted into caustic soda ; mixing these topi
with matte and remelting, the caustic soda is converted into Bodi
sulphide at the expense of the nickel, leaving the latter in a semi-
metallic state, and again a top and bottom is formed with copper and
iron in the top and nickel in the bottom. Bv properly balancing tbese
various treatments a pure nickel sulphide is at last obtained, which
by calcining is converted into oxida This oxide is said to be sopokir
to metallic nickel for the steel-maker*s purpose.

The reduction of the pure nickel oxide is brought about by miziB^
it intimately with charcoal, and heating it to whiteness in graf^tt
crucibles, where it assumes the metallic condition. When molten, it
is granulated by pouring into water. To produce it in oohereot
close-grained masses, the oxide is mixed with finely-powdered wood-
charcoal, or with flour or starch made plastic with molasses, and tiie
mixture is moulded and packed in crucibles with charcoal, ^ hett
applied being just short of that required for fusion.

According to Rickard,f in New Caledonia the ferro-nickel prooBBi
is now beine adopted, as follows : The ore is smelted in a 40-ft. hhtft-
fumaoe to obtain ferro-nickel, which is then ground and decarbooited {
in a reverberatory furnace, and in subsequent treatment the ixoo, ^
silica, and the manganese are slagged off^ and the product is sent
be refined ; the refining is, however, very costly.

Some of the leading proposed modifications not yet adopted mr
be mentioned. .

From researches on the magnetic qualities of the several minenii
in the Sudbury ores, J. T. McTighe and T. A. Edison have sepsrattlj
claimed to be able to effect magnetic separation. Seeing that M^^
mineral must first be reduced to a very fine state of division (at ooc
siderable cost) before admission to the machine, and that dean sepfr
ration is impossible, in view of the fact that it is dependent only o^
comparative degrees of magnetism between the nickeUferona a»2
non-niokeliferous portions (even supposing that to hold good in all
cases), it hardly seems a feasible project.

Macfarlane proposes to treat nickeliferous pyrrhotite by a
cation of Henderson's chlorination process for copper pyrites thu

* B. M. Tbompeon, Mineral Indnstry, 1893, p. 357.
t DisouBsion on Garland's paper.



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METALLIFEROUS MINERALS. 581

(a) roast to bum off the greater part of the sulphur ; (&) mix the
roasted ore with about \ its weight of oommon salt (sodium chloride)
aud reduce the mixture to powder ; (c) calcine the mixture at a low-
red heat; (d) lixiviate witn hot water; (e) add a small quantity of
caustic soda to precipitate any iron ; (/) add sodium sulphide to pre-
cipitate any copper ; ((/) add caustic soda to precipitate the nickel as
hydrate.

Probably the most important modification of present methods will
follow from the discoYery of Dr. S. H. Emmens * that the nickel in
pyrrhotite is eaaily dissolved by a solution of ferric sulphate, even if
the ore be in a raw state,* but it is greatly accelerated by a preliminary
low-roast. He therefore proposes to replace the ordinary roast-heaps
and smelters by weathering-floors, a low-roasting furnace, and lixivi-
ation tanks ; the product being obtained and shipped to t^e refineries
in the shape of either cryst^lised nickel sulpimte or precipitated
nickel hydrate. The simplicity, economy, and high concentration
power of such a method are obvious, and will certainly claim atten-
tion for it.

The Mond process looks very attractive as a laboratory operation,
but it is not free from difficulties. It is based on the discovery that
carbon monoxide (CO) brought into contact with finely-divided nickel
below 300^ F. forms a readily volatilised compound of 1 molecule
of nickel and 4 of carbon monoxide. This "nickel-carbon-oxide,"
Ni(CO)4, is a colourless liquid boiling at 110° F., and its vapour, when
heated to 356° F., becomes decomposed into metallic nickel and carbon
monoxide. As applied to pyrrhotite, the mineral is first pulverised,
then dead-roasted to complete oxidation (not easily attained) ; next
the oxide is reduced to a nnely-^livided metallic state by the action of
hydrogen at 660°-760° F. ; this metal is subjected at 120° F. to a
current of carbon monoxide, which carries off the nickel as Ni(C0)4,
leaving all other metals behind (except some iron which also volati-
lises); finally the vapour is passed through tubes heated to about
356° F., when the nickel separates out in coherent metallic masses.
The finely-divided metallic powder soon loses its energy in the
presence of carbon monoxide, and requires revivifying by heating up
to 570°-660° F. in a current of carbon monoxide or hydrogen, and
cooling down again ; and an enormous amount of carbon monoxide
free from oxygon or halogens will be required in practice.

Oammetce. — The output of nickel ore fluctuates greatly. Thus the
New Caledonia exports were over 10,000 tons in 1884, under 1000 in
1886, 8500 in 1887, dropped to 6500 in 1888, and reached 35,000 in
1891. The metal production in 1891 is estimated at over 10 million
lb., of which New Caledonia furnished more than half, Canada about
4^ million lb., Scandinavia about 160,000 lb., and the United States
120.000 lb.

It has been computed f that the cost of Canadian pyrrhotite
delivered at the breaker is not less than 20«. a ton, and the costs of
succeeding operations are ^ven as follows : — breaking, la. 3d. ; heap-
roasting, 2k ; cupola smelting, 9a. ; bessemerising, 8«. ; reverberatory
calcining, 5«. ; reverberatory fusion, 14s. ; refin^ sulphide roasting,
* Mineral Industry, 1893. f Emmens, op. oit

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S82 ECONOMIC MINING.

20a. ; chlorination and lixiviation, 16«. From ibis it is dedaoed tkt
the cost per ton of nickel oxide carrying 76 per cent metd
will be : —

{a^ From pyrrhotite : breaking, 35«. ; heap-roasting, 58#. ; matte
smelting, 15Z. : beesemerising, 40«. ; first calcination, 13». ; chliirina- 1
tion and lixiviation, 40«. ; second calcination, 9«. ; second faeioB,2oi.; i
pulverising refined sulphide, 2«. ; first sulphide roast, 20«. ; seoond
pulverising, 2«. ; second roast, 20«. ; total, 28/. 4«

(6) From gamierite : smelting for matte, 7d«. ; first calcinatitm,
10«. ; first fusion, 28«. ; second calcination, 9«. ; second fusion, 25*.;
pulverising refined sulphide, 2«. ; first roast of refined sulphide, 21k;
second pulverising, 2«. ; second roast, 20» ; total, 9/. 12«.

Assuming the oxide to be sufliciently pure to require no interme-
diate refining, and to be reduced direct to granulated metal, the coKt
of this operation is calculated at 4d. per lb. of nickel made. E«cko!i-
ing also that the extra richness of gamierite iN counterbalanced I'V
greater freight charges, and that the nickel in the ore costs about ^
same whether it be in pyrrhotite or gamierite, viz. 6«J. a lb., then the
ultimate cost per lb. of metallic nickel will be : —

(a) From pyrrhotite : mining and transpoi-t, 6<i.; conversion into
oxide, 4^. ; reduction into metal, Ad. ; loss in working, 2i. ; total,
1«. ^\d.

{h) From gamierite: mining and transport, 5J. ; con version hito
oxide, Ij^.; reduction into metal, 4c/.; loss in working, j^; total
\\d.

It is to be noted, however, that the calcinations and fusions of tk
matte in the case of gamierite may amount to five, thus incresfflng
the cost; but the metal is completely iree from arsenic.

Market prices fluctuate considerably, as the refining trade is in
few hands, but 2«.-2*. fid. a lb. for 98-99 per cent, fine metal is about
the average.

The great consumption is for nickel-steel armour-plates ; also fur
coinage, domestic articles, and plating.



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METALLIFEROUS MINERALS. 583



PLATINUM.

This metal • is quite widely distrLbnted geographically, but usually
in very small quantities. Geologically, not much is known about the
conditions of its existence, because it is almost entirely encountered
in alluvial formations. Kecently, however, during explorations on
Mount Soloviefif, which lies at the head of the platiniferous gravels of
the Urals, a piece of rock over 1 ft. diam. was encountered, consisting
of chrome iron and serpentine in alternate bands, associated with a
small quantity of dolomite, and some disseminated angular fragments
of country rock. Visible grains of native platinum could be distin-
guished by means of a lens, but even the rock in which no platinum
grains could be seen was found to contain 0*0107 per cent, of that
metaL The platinum is therefore present in microscopic accumula-
tions. The country rock of Mount SoloviefT consists of angular grains
of olivine, cemented by dear green serpentine, and besprinkled to a
small extent with grains of chrome iron ; it may be regarded as the
variety of peridote known as dunite ; this is sometimes massive when
in contact with the including rocks, and at other times shattered and
penetrated by the latter. Moreover, the richeut alluvial deposits are
found lying on serpentine. In California, the placers containing
platinum are always in close proximity to serpentine. In Canada, it
is associated with nickeliferous pyrrhotite in the '* greenstone " group
of diorites and diabases. The platiniferous alluvials of Colombia
consist largely of diorite, carrying chromic iron ; and the alluvial
platinum found in British Columbia is associated with chromite in
deposits resulting from the erosion of diorite. In New South Wales,
it is found in situ in ferruginous felsite and granite, and in gravels
^i^ly composed of serpentine. MineralogicaJly, platinum is nearly
always alloyed with iridium, osmium, palLidium, rhodium, or ruthe-
nium, in the metallic form ; but a notable exception is its occurrence
as an arsenide, sperrylite ^containing 52^ per cent, platinum, 41
arsenic, 4^ tin oxide, | rhoaium, ^ antimony, and * 07 iron), in the
nickeliferous pynhotite of Canada.

Present commercial sources of platinum are all alluvial, though
the vein matter of the Macdonnell mine, Ontario (which carries as
high as '53 per cent, platinum sometimes), and the nickel oxide
prepared from the Sudbury ores (which averages '25 per cent,
platinum), will probably soon be made to yield their quota. In
order of importance come the placers of Eussia, Colombia, British
Colombia, California, Brazil, Borneo, New South Wales, New Zea-
land, &c.

• See C. BulujaD, ** The Platinam Group of Metals,'* Miucrul ludustry, 181)3,
p. 373.



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S84 ECONOMIC MINING.

Bussia virtually supplies the world's demands. The dig^ginji;! now
worked are at Goro-bJagodat (Government) and at Nijni-Tapkk
(Prince Demidoff), neither being auriferous to any extent ; aUo at
Bogoslowsk, Miask, aud New Jansk, where gold predominates. All
the platinum-hearing streams of the Nijni-TagilKk district deeoend
from Mount SolovieCcmd the country around is covered with rormded
boulders of serpentine and peridotite rock. As these boulders deooo-
pose under the action of the air, they form a sand or gravel from
which the metal can be profitably extracted. The platinum of the
aUuvial deposits occurs in grains, or sometimes in nuggets, of whidi
one at least has been found of 22 lb. weight. I'he gravel often ood-
tains \ oz. per ton of platinum, but can be profitably worked for
iV oz. The deposit near the banks of the Kiver Martiane rests on t
serpentine conglomerate, and is 12-15 ft thick. Above is a thi<^Be«
of 70 ft. of barren ground, chiefly clay. Most of the alluvial aariferooi
deposits in which platinum is found are in the neighbourhood uf
peridote rock or of serpentine rock formed by the partial alteratkn uf
the peridotite. Thus the river Miass takes its source from \
mountainous district mainly composed of serpentine rook, and sooth-
ingly the auriferous deposits near the head of the river are rioh is
platinum^ but farther down stream, as the serpentine formation i§ M
oehincU the gold becomes less platiniferous. The richest deposit uf
the Nijni-'J agilsk district is that of Avrorinski, extending for a longUi
of \ nule, 20-60 yd. wide, and of a thickness of 4-5 yd. Hero tk
platinum iH found to the amount of 4j^, 5, and sometimes even 9 <&
per ton. The metal contains a small proportion of gold, about -2^
grm. per kilo., which is separated by amalgamation. The cnde
platinum left contains about 90 per cent, pure platinum, froa
October 1886 to August 1887 the production at Avrorinski wtf
40,476 oz.

On the mines of Prince Demidoff,* the platinum-bearing sand a
found at a depth of 6-40 fL, the •* pay-streak," which is 6-10 ib.
thick, resting directly upon serpentine bedrock. When the over-
lying gravel is not too thick, it is thrown to one side, and the *'fnj
sand " is then scraped up ; but, as a rule, shafts are sunk to the bec-
rock, and the sand is removed by drifting. This work is done daricc
the winter months, the sand being piled to be washed during tbe
summer. The sand to be washed is carted upon an elevated pla^rs.
from which it is fed with water into a revolving conical screen, tt^
platinum and fine sand passing through into the sluioe below, whik
the coarse materials are discharged at one side and carted away. Tk
sluice consists of an outer and an inner compartment, the latter beaoc
kept locked, and opened only once every 24 hours by a governmefit
inspector. The tailings from the first compartment, in which rm^
of the platinum settles, enter the second, where they are puddled as:
raked by women, the coarse part being thrown to one side to» far
carted away, while the fine sand pabses into a tail sluioe. Tte
machines run continuously, are driven by steam, and attended I?
men and women working in shifts of 12 hours each, with » r»t «[
4 hours. Each machine has a capacity of about 400 metric tow ^
• G. F. Kunz, Minezal Indnstry, 1893, p. 379.



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METALLIFEROUS MINERALS. 585

sand per 24 hours, yielding over 5f lb. of metal, or a total daily out-
pnt of 11^ lb. During the summer months, 8000-8500 men and
women are employed; during the winter but 1000. The eost of
washing at the Demidoff mines is as follows : — 40 oarts and drivers at
3«. 9fi. = 72. 10«. ; 16 men at 2«. 8d., IZ. 16<. ; 4 women at 1«. 8(2., 5«. ;
total per machine per day, 92. 11«., not including cost of fuel, engineer,
Bhovellers, interest, depreciation, <&o.; this would make the cost of
washing about 2d, per metric ton of sand washed. ISand containing
less than 8 grm. per ton cannot be profitably worked, although a few
instances of sand containing only 2*5 grm. per ton and worked at a
profit can be cited. These costs probably do not vary much from
those of the northern or Government district. In the Goro-Blagodat
district the Government has granted 70 concessions, and the output
is considerably larger than in the southern district. All the platinum
produced pays a tax of 8 per cent, in kind to the Government. The
average yield of the Demidoff estate during 1801 was, according to
Knnz, 6-55 grm. per metric ton. The report of the Bussian Depart-
ment of Mines, 1892, states that during 1890 the total amount of
pktiniferous sand washed in the empire was 778,158 tons, yielding
2836 kila of platinum, an average of 8*8 grm. per metric ton ; and
>n the Demidoff estate, 288,200 tons, yiel£ng 865*7 kilo., being an
iverage of 8*06 grm. per ton.

In Colombia the chief and the only washings of importance are
found in the Province of San Juan, Department of Cauca, formine the
Kmthem part of what is known as El Choco. The principal locaTitieB
ire the districts of Sipi, Taman4, Condoto, Iro, and San Juan, in all
)f which the metal is found associated with gold. Platinum is also
Ibund in the Atrato and its tributaries, in Antioquia, and in the
iistrict of Barbacoas. The bulk of the product is from the ealiche
)eds, which Bulman * asserts to be glacial drift, and in which diorite
letritus is very common. The deposits are ground-sluiced in a
udimentary manner, and the heavy sand is scraped up and washed
n bateas. The gold and platinum are placed on a porcelain plate,
^d separated by gently and regularly tapping on the edge. Nearly
il the ealicke deposits were found by Bultuan to yield j^l grm. per
ub. metre, and many of them could be worked by hydraulicing.
[lie present yield is about 250 lb. yearly, but it used to be very mucn
urger, and could easily be increased by systematic working.

In British Columbia, important deposits of platiniferous gold
ravels are found on the Similikameen Biver and its tributaries,
specially the Tiilameen. It is also found in the Frazer hiver dis-
net, near LiUooet. Hitherto it has not been diligently sought for,
ut is simply recovered as a bye-prod act of the gold washings. The
atput is 60^120 lb. per annum.

In California, platinum frequently occurs, associated with iridos-
line, in the auriferous gravels ; in Humboldt County it is found in
le auriferous sands of the Gold Bluff Beach, near the mouth of the
ian&ath River. The yield from the gold placers of this State and
"regon constitute the total production of the United States, which is
[>proximately 20-40 lb. yearly.

* En. sDd Min. JL, April 2. 1892.



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586 ECONOMIC MINING.

In Brazil, native platinum oocurs in the auriferous gravels of
Minas Oeraes, associated with iridosmine, platiniridiam, and an alViy
of palladium and gold ; in grains in the auriferous veins of the Bua
Esperan^a in the Province of Parahyba do Norte ; while the gold of
the Gkmgo Soco jacutinga of Minas Geraes h frequently found lUlojcd
with platinum, and occasionally with palladium. The platiniferoos
deposits of Brazil are further distinguished by two very rare native
allovs — porpezite, a palladium-gold alloy occurring at Porpez, and
rhoaium-gold. The annual production is now very smalL

In Borneo; platinum is found in certain auriferous gravels of
which little is known, although some years ago it was reported tlixt
600-800 lb. a year were being extracted from them. The rare niinenl
laurite (ruthenium sulphide) occurs there in small quautities with the
platinum.

In the Australasian Colonies, platinum has been found in the
sands of the Richmond and Tweed rivers, and in the Broken Hill uree,
New South Wales ; and in the sands of the Tayoka river, the quarts
of the Qaeen of Beauty mine, and in considerable quantitiee at
Hokitika, New Zealand . Broken Hill ore carrying 2 * 78 grm. platinum
per ton was concentrated up to 15-28 grm. per ton on Fme vaoners,
but not with commercial success.

Treatment, — The preparation of pure or partially pure platinnni
from its ore and alloys is an industry which is practically a monopoly
and which demands very large capital ; it in virtually controlled bv
Johnson, Matthey and Co., London, and needs but brief deecription
here. The method pursued by them is, in outline, as follows. The
crude metal is treated in a reverberatory furnace with an equal weight
of galena. When the platinum has formed an alloy with the 1^
reduced by the iron in tne ore, ground glass and borax are added u
fluxes. The osmiridium does not alloy with lead, and gradoally
settles to the bottom by virtue of its high. specific gravity. The
sulphur is then oxidised bv the addition of Htharge. Finally the
slag is skimmed off, and the metal is run into ingots, which upoa
cupellation yield platinum containing some iridium and rhodium.
Such metal is well adapted for ordinary uses, and the cost of the
operation is given at about (yd, a lb. when working on 200 lb. lot^.
If greater purity is demanded, this metal is melted with 6 times its
weight of chemically pure lead, which is then granulated and treated
with nitric acid diluted with 8 parts of water. Part of the lead, and
the cupper, iron, palladium, and rhodium are disnolved, leaving «
black amorphous powder containing platinum, lead, and small quanti-
ties of the other metals present ; the iridium existing ax a brilliaDt
crystalline substance insoluble in nitric acid. This residue is treated
with dilute aqua regia, which dissolves all the platinum and lead, bat
not the iridium. The solution of the chloride is evaporated to asniall
bulk, and sulphuric acid is added to precipitate the lead. To the
filtrate, ammonium and sodium chlorides are added, precipitating the



Online LibraryCharles George Warnford LockEconomic mining: a practical handbook for the miner, the metallurgist and ... → online text (page 66 of 76)