Charles George Warnford Lock.

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\ cwt. lime and 1 cwt. coal. The blast is supplied by a Baker blow^.
and as the lead is melted it runs over into a receiver, from which it is
cast into pigs, which are afterwards desilverised. The peculiarity ol
this process is that it makes comparatively little difference wheUier
the lead is obtained in this or in a subsequent operation. A hot and
strong blast can therefore be used, and labour is greatly economiiwd ;
4 men, 2 on each side, can smelt 7 tons of ore in 8 hours ; or 12 men«
working 3 shifts, can put through 21 tons in 24 hours. An additional
man can bring all the coal and mne required. By the Scotch health,
a similar yield would have required 32 men. Leas skilled men may
be employed. The slag and fumes, together with considerable second-
grade ore, are treated in the pigment furnaces, water-jacketed lov
cupola blast famaoes. The charge produces in these fumaoee a
portion of metallic lead, and a large quantity of lead sulphate vdati-
fises. The vapours are oxidised, and drawn by a fan through ccm-
ducting pipes into bag condensers. This sublimed white leadj
consists mainly of an amorphous sulphate and oxide of lead inci-
dentally containing 4-5 per cent, zinc oxide. The produc^on of
this material grew from 3^ million lb. in 1890 to 8 million in
1893.

The process has lately been established at Canon City, Colcu^o,
on argentiferous zinc-lead sulphides, carrying 2-30 per omt. lead,
12-28 zinc, 10-38 iron, 0-10 copper, 5-38 silica, and 4-29 <». silvo-.

• Prof. W. BamBay, " Lewia-Burtlett Process of Lead Smelting,** JndttstrMv;
E. W. Hftwker, •* The F. L. Bartlett Zinc-Lead Process ; " P, P. Dewev, -Lewa-
Bartlett Bag Process for catching Lead Fumes," Trans. Amer. Inst Im. Engi^
xviii. 674.



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METALLIFEROUS MINERALS. 553

The reqnisiies for suooess are: — (1) Oheap flaming fael — e. g. bitu-
minonB ooal ; (2) iron ore either as oxide or pyrites, the latter being
especiallj desirable if it contains silver; (3) oopper ore containing
about 3 per cent, copper for the formation of copper matte to collect
the silver.

Ores containing 25 per cent, zinc and over are crashed to pass a
4-inesh screen, ana mixed by an Archimedian screw with an equal
balk of fine coal. The mixture is moistened and charged in lots of
600 lb. into a furnace, of which the grate consists of perforated plates,
the charge being spread on the grate in a layer about 4 in. deep. Air
is forced through the charge from below at a pressure of about 2 oz.
per sq. in., and a sufBcient quantity of air is also forced through
openings in the sides of the furnace above the layer of the ore to
prevent the formation of sulphuric acid with the hydrocarbon vapour.
The burning is completed in about 4^ hours, when the charge, which
has not been touched during the operation, is in the form of a sintered
mass, ready to go to the blast furnace, containing the silver and other
Qon-volatiie metals and some zinc. All the lead, and most of the zinc,
is volatilised, and collected in the form of fume, out of which the pig-
ment is made. Iron pyrites, when neoessary for a flux, is charged
Into a somewhat similar furnace and treated in a sitnilar manner,
except that only enough slack coal is used to start the pyrites burning,
their sulphur contents being sufficient to supply the requisite fuel
tieat, whue a higher blast (4 oz. per sq. in.) is used, the burning being
completed in |-1 hour. Sinter from the zinc ore is mixed with the
3umed pyrite, copper ore, fluxes, and fuel in the requisite proportions,
md is smelted at a high temperature in a water-jacketed furnace of a
greater proportional length than that of the ordinary blast furnace.
Host of the zinc left in the charge passes off in the form of a fume,
^hich is saved, while the copper matte which collects the silver runs
nto an outside crucible with the slag, and is tapped from time to time.

Ores containing about 22 per cent, zinc or less are smelted directly
Q a special furnace with the jproper mixture of copper ore, fluxes, and
uel. This furnace is water-jacketed, and has two rovra of tuyers on
ach side, the upper ones being about 10 in. above the lower. The
>wer blast is supplied under a pressure of about 2 lb. per sq. in., and
% preferably a hot blast. The upper blast is cold, and run under a
ght pressure. The ore and fuel are fed together continuously in a
bin layer 12-18 in. deep. For fuel, a mixture of coke and coal
greenings is used, amounting to \ the weight of the ore. The blast
-om the lower tuyers plays upon the bath of molten matter, scorify-
ig it, and volatilising all the lead and most of the zinc, which pass
or, thjTOUgh the thin myer of the unmelted portion of the charge, in
10 form of fume. The upper tuyers deliver a blast at the top of the
larK^ thus serving to keep up the necessary combustion, and prevent-
Lg the condensation of the volatile compound rising through it. The
>pper matte which collects the silver, as in the first method, runs
ito an exterior crucible with the slag, and is tapped occasionally.

The matte contains as much as 65 per cent, oopper and 250 oz*
Iver per ton. The slag contains 6-10 per cent zinc and f-1^ oz.
I ver per ton of ore treated, no lead, and only a trace of copper.



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554 ECONOMIC MINING.

The fumes from all the furnaces, oonsisting of &e zinc, lead, a&d
other volatile elements, are drawn forth into chambers by means of
exhaust £Bkns, and then forced through iron cooling conduits into long
bags hanging &om the roof of a building at some distance &om the
smelters. The gases pass through the bags, where the solid oont«ita
of the fumes are caught, from time to time shaken down \nto can,
taken to the refinery, and subjected to a low-red heat in a doeed tube
containing a screw, which keeps the material in constant motion. By
t^ means aU the deleterious volatile elements are removed, and tli^
product is a marketable white pigment containing 35-40 per cent
oxysulphate of lead and 55-60 per cent, zinc oxide.

Some ores lose silver heavily and others hardly any, oree oontain-
ing copper or iron pyrites losing much less than others. Ab mudi as
95 per cent, has been recovered, but generally the salva^ is between
70 and 85 per cent. Theoreticallv, the loss of silver should be confined
to that in the pigment and that in the slags, L e. in the former aboat
1 oz. and in the Tatter 1^-2^ oz. per ton of ore treated; but there is &
variable loss somewhere between, which has never been disooveied.
(Later returns show the silver loss to be under 2 oz. per ton of ore
treated, while there was a gain in the lead and gold over the assay of
the raw ore\* The cost of treatment at Canon City is 2O-40«. (average
25<.), incluaing the production of the pigment and matte. The prio&
of slack coal delivered at the works is 2#. per ton ; of coke, 20^. per
ton at Canon City. The cost of a plant to treat 250 tons of ore per
day, producing about 20 tons of pigment and 40 tons of matte, is
60,0002.

(6) The Pamell process was successfully worked for some years
near Swansea. It depends on the fact that when blende is roasted
l¥ith access of air, the zinc is converted partly into oxide and partlj
into sulphate, both amenable to lixiviation, the former with water
and the latter with dilute acid. The following operations are en-
tailed: — ^roast at low heat; leach with water; heat residue with
dilute snlphuiic acid in revolving lead-lined pans ; leach with water
and add liquor to previous one; precipitate copper by scrap iron;
evaporate liquors down to a moist paste ; add \ of its dry weight of
finely powdered blende ; dry ; calcine in muffle ; smelt residue of zinc
oxide. The leached ore after calcination makes an argentiferous iron-
lead suitable for ordinary smelting. The sulphurous acid escaping
from the blende roaster and from the sulphate caloiner is utilisea for
making sulphuric acid. Jhe yield was 80 per cent, of the zinc in a
metallic form, with a loss of 4 per cent, each of the lead and silver.
The cost is about 25<. a ton in Wales, where the sulphurous acid is
utilised.

(c) The West process * has found successful application on zinc-
lead sulphides from the Silver Valley mine. North Carolina. The
operations are : — ^roast ; cool ; moisten with water ; place on a layer
of pebbles in a false-bottomed tank ; force the sulphurous acid firom
the roaster with a jet of steam through the ore in the tank, thus con-
,,«^;^gr the oxide into sulphite and ultimately sulphate ; remove tiw
"separate tank ; leach with water ; pass gaseous ammonia into
RDunenp, ** Treatment of Zino-Lead Sulphides," Mineral Indoaliy, 189&

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METALLIFEROUS MINERALS. t,t,t,

the liquor, thus precipitating zino hydrate ; transfer liquor (ammonium
sulphate solution) to a still, add lime, and heat, reKenerating ammonia ;
dry the leached ore (containing the iron, lead and precious metals) on
an iron floor heated by the roaster, when it can be smelted in the
usual way. The process is much too complicated and costly for wide
application, and only affords 80 per cent, of the lead and 70 per cent,
of the zinc (as oxide^ at best.

(d) Electrolysis (with a carbon anode) may be applied to the zino
solution for liberating the sdnc as metal, and the acid solution may
then be used for treating fresh quantities of zinc oxide, thus making
the consumption of acid almost nominal. This feature has been taken
advantage of in the Letrange, Siemens-Halske, and other processes,
bnt is not yet developed in a practical and economical form, the plant
being too costly for a limited output.



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556 ECONOMIC MINING.



MANGANESE.

Though manganese is very widely disseminated, it is often onlyu
gan^e matter possessing no valne ; its combinations and associatuws
in t£is character are exceedingly nnmerons. On the other hand, its
industrially useful ores are veiy few and not commonly enooonteied
in great bulk ; they are confined to oxides and (rarely) carboniie.
Of oxides and hydroxides there are also a number possessing no com-
mercial value. Practically the only ores sought and mined are ss
follows : —

Pyrolusite, or peroxide, MnOj, with 63 per cent, manganese.

Braunite, or sesquioxide, Mn^Os, with 69 per cent, manganese.

Psilomelane, of indefinite composition, containing bitriiun and
other impurities.

Manganite, or hydrated sesquioxide, MujOsyHjO.

Diallogite, or carbonate, with 45 per cent, manganese.

The ores are rarely found in such a state of punly as to be deemed
specific minerals ; they are rather mixtures in all proportions of tk
several oxides with ferrous and ferric oxides, silica, piioephoma, ^
Sometimes an attempt is made in the trade names to distinguidi the
quality of the ore : thus — " pyrolusite " when the assay gives nearly
80 per cent, peroxide (MnOj), " black oxide " when it runs below 75 per
cent., and *' manganiferous iron ore " when the percentage is verj low:
but these distinctions are arbitrary and useless. Manganese occnrrii^
with silver ores is sacrificed to the more valuable metaL M»b*
ganiferous iron ores have a usefulness in making spiegeleisen eTe
when low in manganese ; and a similar application is found for tk
manganiferous zinc ores of Franklin and Sterling, New Jersey, after
extraction of the zinc, the residue being known as '* clinker."

The British home production of manganese ore is now bo ridics-
lously disproportionate to our consumption — about 800 tons as agaiz^
a yearly importation of over 100,000 tons — that but little intew*
attaches to it, and apparently it is dying out. The greater part Ij
far is mined in Merionethshire, and is of very poor quality except it
freedom from phosphorus, giving 80 per cent, manganese, 24 ua^
2 iron, and * 02 phosphorus.

The French mines at Las Cabesses,* Pyrenees, are remari»l^
producers and geologically interesting, the exhaustion of the saife*
deposits of black oxide (pyrolusite) having led to the disooreiT <'
lower accumulations of impure carbonate (diallogite), contaiDit|
45 per cent. metaL The geological formation is shown in Fig. ^^
the lower beds a are Silurian schists, overlaid unconformably by ci^^

♦ C. A. Moreing, " The Manganese Mines of Las Cabesses, Pyrenees, ?»■*
Trans. Inat. Min. and Met., iii. 250.



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METALLIFEROUS MINERALS. 557

schists h (Lower Devonian), which pass imperceptibly in plaoes into
mixed strata of grwUt or spotted marble and limestone c (Middle
Devonian), followed by a bed d of pure qrioifA (Upper Devonian), and
this by the coal measore shales e.
The manganese deposit is concen-
trated at /, but all the Devonian
beds contain a percentage of the
metaL The rich deposit /has been
opened for a length of 200 ft., a
width of over 160 ft., and a depth
of 230 ft. The strata strike E.-W.,
and dip regularly N. about 72°.
The formation of .the deposits is
attributed* to metasomatic inter-
change between the limestone and Fio. 158.— Manoakbsb Deposits,
manganiferous solutions-; their dis- ^^ Cabbbsibs.

tribntion is very irregular, and

well-defined boundaries are wanting. The output is now about
100 tons a day.

Spain possesses important deposits! of manganese as lenticular
masses, situated along lines of weakness, and probably consisting
originaUy of carbonate which has subsequently been altered by
silicioos solutions, and the outcrops oxidised by atmospheric agencies.
The surface workines are on black oxide, changing in depth to
carbonate (diallogite; and silicates (tephroite and rhodonite). The
average contents are 40 per cent, manganese (raw), 12-20 silica, and
•l-*2 phosphorus. The silica can be to some extent reduced by
hand-picking ; and the black oxide and carbonate ores do not exceed
*08 per cent, phosphorus.^

Very important deposits of high grade ore, carrying 56-62 per cent,
manganese, and only * 83-2 -30 silica, and * 74-1 -85 phosphorus, are
now being energetically worked at Covadonga, and will probably soon
have an influence on the market. The mineral can be delivered in an
English port at a cost of little more than 30«. a ton.§

The Caucasian deposits are very extensive, forming a vein 2-8 ft.
thick which outcrops on both sides of the river Ewirua, near a town
of that name on the Baku-Batoum railway. Mining and transporta-
tion are in the crudest state, and only about one-third the product
comes to market. Assays show about 55 per cent, manganese, li^6j^
silica, and -15- -2 phosphorus.

Sweden affords a small quantity of ore showing about 47 per cent,
manganese, 16 silica, and -01 phosphorus.

Indian manganese ores average 49 per cent, manganese, 3 silica,
and * 13 phosphorus.

Japanese shipments go high in metal (52 per cent.), but carry
9 silioa and * 1 phosphorus.

• E. Hooper. t O. E. GolUns. X W. G. Bowie.

I See J. A. Jones, *'The Govadonga Manganese District and its Mines," and
F. Johnson, ** The Manganese Deposits of HueWa," in Trans. Inst Min. and Met,
Marohl895.



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5S8 ECONOMIC MINING.

Most of the manganese ore of the United States* is prodnoedin
the States of Virginia, G^rgia and Arkansas, mentioned in tbe order
of the quantity of ore raised; while smaller amounts are derived
from Leadville, Colorado, San Joaquin County, California, and the
Lake Superior region of Michigan. The Crimora mine, Virginia, ii tiie
largest in the country. The containing clay bed is over 300 ft. ihict
The ores occur in pockets, which as a maximum are 5-6 ft. thick and
20-30 ft. long, and of lenticular shape. Other irregular stnngen
and smaller masses run through the clay, which preserves the strne-
ture of the original rock. Potsdam quartzite underlies it. Aooordiiig
to C. K nall,t black oxide of manganese occurs in the Potsdam Band-
stones of this region in greater or less amount. It is often noticeable
as a black stain on the rooks or as minute specks or particles through-
out the mass, but no workable bodies have been found within ^
Potsdam sandstone. He concludes that the ore originates from the
Potsdam sandstone, where it exists disseminated throughout the
rocks. The water draining from the mountain area east of the daj
basin carries the mineral with it in minute quantities, and redepositi
it in the clay which fills the basin. The largest and best depodts of
ore have been discovered directly beneath the course of the brook ai^
immediately upon its entrance to the clay area. The ore is found in
irregular bodies in various parts of the clay mass. Clay seems to he
essential to its formation or redeposition. It is seldom found in saodj
ground, and, when it is thus found, one is led to the belief that ckj
originally formed part of the mass, and has been subsequently wished
out. A piece of sandstone imbedded in clay will sometimes beoosae
so much impregnated with the black oxide of manganese as to be in
fact a silicious manganese ore. To Hall's mind it appears that the
water, laden with its particles of manganese minerals, becomes reuid^
upon reaching the (day mass, and a separation takes place more or
less rapidly. The high-grade ores contain 48^-50^ per cent, man-
ganese, 10 silica, and *09-*l phosphorus.

Other similar bodies occur at Lyndhurst and elsewhere in th«
Great VaUey of Virginia. Less important deposits are found at
higher horizons. Cartersville, Oeorgia, is second to Crimora in pro-
duction. The ores again occur in pockets in a stiff clay, and art
associated with quartzite, which may be Cambrian (Potsdam) ^^
Upper Silurian (Medina). They contain 34-44 per cent, mangane^.
7-16 silica, and 'OS-* 16 phosphorus.

The manganese deposits of the Batesville region, Arkansas, (Kxnx
in an area of Silurian and Carboniferous rocks. The ores are ^^
in a red clay, which has resulted from the decay of a crystalfe*;
Silurian limestone (St. Clair), called by the miners "grey wek.
The deposits are usually capped by a mass of broken chert 1-60 f-
thick, of Lower Carboniferous age ; it represents the remains of »
solid stratum which originally overlaid the St, Clair limestoifc
When the limestone decayed, the chert sank down on the res^^
day left by the limestone, and became distorted and shattered. Ti^

♦ E. A. F. Penrofle, • Manganese; its Uses, Ores, and Deposits,' 1^0.
t " Notes on the Manganese Ore Deposit of Crimora, Virginia," Tran*. S»^
Inst. Min. Engs., June 1891.



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METALLIFEROUS MINERALS. 559

ore in tlie clay occurs in mticli the same way as it did in the original
limestone ; that is, in irregular pockets, masses, sheets, or as scatteiied
nodules. Sometimes the clay is barren of ore for considerable dis-
tances; at other times the ore is abundant. In some places, where
the limestone has not decayed, the ore can still be seen in it in sUu.
The ores contain 50-53 per cent, manganese, 1*7-2*9 silica, and
•16-* 35 phosphorus.

At Leadville and vicinity, considerable quantities of manganese
and manganiferous iron ores, obtained from the silver deposits, are
used as a flux in silver-lead smelting, or as a source of spiegeleisen
and ferro-manganese. These ores contain 25-40 per cent, manganese.

Quite productive deposits are found in pockets at Markhamville,
King's County, New Brunswick, in Lower Carboniferous limestone.
Some thousands of tons have been shipped. Other mines are situated
ftt Quaco Head. At Tenny Cape, in the Bay of Minas, Nova Scotia,
is another deposit in Lower Carboniferous limestone, which has
furnished several thousand tons of ore. Others less important occur on
Oape Breton. The Nova Scotian ore contains 47 per cent, manganese,
7-8 silica, and '01 phosphorus.

The Virginian and other day deposits are worked by shafts and
] rifts, the loose character of the ground necessitating much timbering,
rhe clay ore is usuallv washed in an iron-ore washer, or in revolving
jylinder screens, or (the smalls) in jigs.

The Cuban * manganese ores are chiefly pyrolusite and psilome-
ane, though wad is found in some quantity. The deposits most
>ccur associated with jasper and in vertical veins, which in places
lave nndergone decomposition into clay. In the latter case it some-
imes happens that several hundred tons of exceUent ore are found in
me body, but for the most part the ores occur as lumps of various
izes, more or less mixed with clay and fragments of jasper. The
arge lumps can be handnsorted, but the small ones can be saved only
»y washing. In some of the mines the amount of '* waste-ore " appears
warrant the erection of a plant to reclaim it The quality of
hipped ore is good, averaging 45-53 per cent, manganese, 4-9 silica,
M *03— * 1 phosphorus. Much of it can be mined in open cut with
»ick and shovel, costing 6s. a ton for mining and 6«. packing, freight
.nd charges bringing up the total to about 50«. a ton in Philadelphia.

Chilian! manganese mining is concentrated in two centres,
]!oquiinbo and Carrizal. The beds worked in the province of Co-
Tiimbo are chiefly surface deposits, requiring no expensive or scien-
ific mining. The cost, therefore, of producing the ore is trifling ;
he ore runs in ridges, the tops of which are visible, the ore being
xtracted chiefly by crowbar and sledge. The great expense, how-
ver, is the cost of transportatiou. The ore from this district contains
onsiderable peroxide, and is softer than that from the Carrizal district,
^he latter is found in nearly vertical lodes of a few inches to about
ft. -wide or more, but the common width is about 3 ft. There were
eavy outcrops on the surface forming waUs or dykes 10 ft. or more
igh. These were worked as open quarries, but now the ore is usually
'orked underground as mines. The walls of the lode are not well
• E. J. Chibw. t J. 'D. Weeks.



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56o



ECONOMIC MINING.



formed, nor is there any natural cleavage between the ore and ths
walls ; the manganese is not regularly continuous for any great •dtf-
taDce ; there are sudden *' faults " or disappearances of the ore, it
having been pushed to one side or other, maMng it difScultto findtbe
lode again. The ore is hard and brittle, with a glassy fracture, and
has no soft powder-like deposits as some of the Coquimbo manganeee.
Every pound of it must be taken out by blasting. Assays of Chiliu
manganese show 50-63 per cent, manganese, 4-7^ silica, and *02-*OS
phosphorus. A very large proportion relatively of the metal ii
present as protoxide. Next to the calcined carbonate of Las CabesKi
it is the most highly prized product for the steel maker.

Australian samples of manganese ore have given 48 per cent, nun-
ganese, 3 silica, and «8 phosphorus; and New Zealand shipments,
63 per cent, manganese, 8 silica, and * 07 phosphorus.

Treatment, — The carbonate ore of Las Cabesses is calcined in kilns
similar to those used for roasting iron carbonate, consisting (Fig. 159)

of a cylindrical i^eet-iron shell a, open
at both ends, lined with fire-brick k
and restiug on iron standards c aboit
3f1
16




Fig. 159.— Makoanese Calcinino J?'

FUBNAOE. Th

for
charging goes on, one layer of ore
about one-third of the kiln is fill<
continued in the same manner to
and on the fourth day the material
bring air into the kiln, and preve:
into lumps. After having thus bej
the kilns are filled to the top with
When charging the kilns for the fi
chosen, so that the draught may
kilns are in operation, the layers n
nmall. The whol^ must be arrang
The third day after, the kilns are fi
to say, the bringing down of the o
ore is added on top. i When the k
the sixth day— there! are 3 drawii



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METALLIFEROUS MINERALS. 561

ours regularly ; and by tluB means S-10 tons caloined ore are drawn
at of ea^ kihi in 24 hours. When the kilns are properly started,
le working only requires care, and drawing and filling at regular
itervals. The ore is broken for the furnace to pieces not larger than
-5 in. square, and the smallest stuff put in is of the size of walnuts,
he proportion of the different materials introduced are : — 14 wheel-
irrows of large ore, with 8 of small stuff, to 2 of coke. The layers
llow each other regularly, and are arranged so that in the centre of
le kilns, as well as at the sides, there is cSways big stuff, whilst the
sail ore occupies the intermediate space; the large pieces of ore
tow the air to circulate, and form a kind of chimney, while the coke
spread out as regularly as possible, and forms a thin cover over
oh layer of miner^. The proportion of coke used is 2^^ per cent.
' weight, of the raw mineral. The loss in weight of ore by roasting



Online LibraryCharles George Warnford LockEconomic mining: a practical handbook for the miner, the metallurgist and ... → online text (page 63 of 76)