Charles George Warnford Lock.

Economic mining: a practical handbook for the miner, the metallurgist and ... online

. (page 42 of 76)
Online LibraryCharles George Warnford LockEconomic mining: a practical handbook for the miner, the metallurgist and ... → online text (page 42 of 76)
Font size
QR-code for this ebook


Digitized by



Google



NON'METALLIFEROUS MINERALS. 371

are, clamped with iron bands and backed with a concrete made
n chips and fragments. The grinding face is dressed all over with
ores. European supplies come from the Silurian, carboniferous
[ old red sandstone grits of England, the metamorphic quartzites
^tland and Norway, and, the best kinds, from the Tertiary sand-
aes of Seine et Mame, France, and the Tertiary lavas of the
ine.

The flint and quartz conglomerate from which American mill-
068 are made is found at different places along the Alleghany
antains. In Ulster county. New York, it is quarried under the
oe of '^ esopus stone ; " in Lancaster county, Pennsylvania, it is
>wn as " cocalico stone ; " in Montgomery county, Virginia, it is
led " Brush mountain stone," and in Moore county. North Carolina,
8 found as ** North Carolina grit."

WheUUmes. — Much finer grain is required in a grindstone, but
erwise its qualities resemble those of the millstone series— hard-
B, toughness, and uniformity of texture. They may be all classed
Bandstones, varying in fineness of grain. British supplies come
^Ij from the coal measures, but also from the old red sandstone,
oolite, and the greensand beds. Kenton, Gk>sforth and Eighton
iks (near Newcastle), Wickersley, Haverley, and Congleton (in
rftsbire), Bilston (in Staffordshire), Craigleith (near Edinburgh),
I many other places afford a useful article.

The still finer grained stones used as hones and oil-stones are
re properly schists and slates of very close and compact texture, in
ich the silica is in an exceedingly fine state of subdivision. The
t known *' batts " for whetting scythes, &c., are obtained from the
rer carboniferous sandstones of Lomond, Fifeshire, the millstone
t and ganister beds of the coal measures in Yorkshire, and the
ensands of the Blackdown hills, Devonshire. The '* rag-stones "
Scotland, Norway, and Russia are highly silicious mica schist, the
t named being the softest. The most familiar of the European
itonee are the " Charley Forester," a corruption of Chamley
wt, Leicestershire, the "Water of Ayr" or "snake-stone" of
rshire, the Welsh date and the Grerman novaculite from the slate
fi around Batisbon ; but better than any of these are the " Turkey
stones " from Asia Minor. Much is also imported from the United
tea.

Of the important American supply of silicious rock used for
rpening edged tools, Arkansas, Indiana, and New Hampshire
ysh the biuk ; a small quantity is produced in Vermont. The
■nsas stone is found in the neighbourhood of Hot Springs, and is
«ed to have been formed by the action of hot water upon the
z formations. It is found in two varieties, known as " Arkan-
and " Washita " stone, the grains in the former being smaller
more compact, of a uniform bluish-white colour, and semi-
parent, while the Washita stone is more opaque, and of a pure
^ colour. In Indiana two varieties also occur, known commer-
f as " Hindostan " and " Orange " stone, the former being white in
r and the latter of a buff or orange tint. The quarries are all
»1 in Orange county. The quarries in New Hampshire are
[ 2 B 2

I Digitized by VjOOQ IC



372 ECONOMIC MINING.

located in Grafton county, and the product consists of " rift sandstone'
and *' chocolate " whetstone. The Vermont quarries are located in
Orleans county, and the product is used exclusively for scythe-«ton€?w
Some *' Labrador" oilstones have in the past been produced at
Manlius, Onondaga county, New York, but tne factory is now used
for the manufacture of oilstones from Arkansas and Washita stone,
The output of the different kinds of sharpening stones in 1889 cos-
sisted of 456 tons of scythe-stone, 1500 tons of rift sandstone, 15 toia
of orange stone, 500 tons of Washita oilstone, 80 tons of Arkanai
oilstone, and
6000Z.



Digitized by



Google



NON'METALLIFERQUS MINERALS. 373



SULPHUR.

The following remarks relate exclusively to native sulphur (brim-
tone). Though the amount of sulphur annually mined in the form
f snlphi'tes of various metals («. g. iron and copper pyrites, galena,
dende, &c.) probably far exceeds that obtained in the uacombined
tate, still, the separation of the sulphur in an utioxidised condition
rom such compounds is never attempted, for the simple rea<)ons that,
D the processes for extracting the suvernl metals from their ores, the
irat step necessary is the elimiuation of the combined sulphur, which
I most easily effected by a roasting or oxidising operation, wheieby
be sulphur is at once converted into sulphurous acid, itself a valuable
ommodity. and, moreover, capable of being readily oxidised one step
arther to form sulphuric acid, the chief purpose for which sulphur is
Dnsamed.

Italy and Sicily together furnish the greater part of the sulphur
f commerce, the major portion coming from Sicily. As to the geo-
3gical history of the sulphur beds of that island, it has been supposed
bat at the end of the Middle Miocene period the sulphur-bearing area
ras raised, and lakes were formed in which occurred the deposition of
lie snlphur rock and its accompanying gypsum, tripoli, and silicious
ime^stoDe. The sulphur r<K5k is composed of sulphur and marly lime-
tone, the sulphur being sometimes disseminated through the limestone,
nd at others forming thin alternate layers with it. These sulphur-
earing seams are often separated by layers of black marl, 20 in. to
ft. thick, some seams attaining a thickness of 28 ft. The total
ggregate thickness of the sulphur seams reaches 100 ft. in one case,
«t the average total is 10 to 12 ft. only. All the seams are decom-
osed at their outcrop, and show only an accumulation of whitish
riable earth, called hriscale by the miners, and n ai ily composed of
ypsum. This has resulted from the oxidation of the sulphur to
alphuric acid by atmospheric agency, the acid in turn attacking the
me carbonate, and forming sulphate (gypsum). The most plausible
apposition as to the origin of iiie sulphur seams would appear to be
bat the lakes received streams of water containing calcium sulphide
\ eolation, this calcium sulphide probably resulting from a reduction
f the masses of calcium sulphate (gypsum) by the action of volcanic
eat Gradual decomposition of the calcium sulphide in the presence
f water would finally result in a deposition of sulphur and of lime
arbonate, in the relative proportions of 24 and 76 per cent. As a
latter of fact, much of the Sicilian ore actually has this percentage
imposition. Whatever the process has been, it is no longer in
ctirity, and there is no growth nor renewal of the beds, in this
Bspect differing essentially from recent deposits due to ** living "
olfataric action.



Digitized by



Google



374 ECONOMIC MINING,

The sulphur country lies to the south of the Madonia cliAhi
mountains, embracing nearly the entire provinces of Caltanisetta u
Oirgenti to the seaboard, and part of that of Catania ; in addition
these, there is a group of mines in the south of the pxoTinoe
Palermo. The principal centres of this industiy are at the inin«
Caltanisetta, Castrogiovanni, Montedoro, San Cataldo, Serradifal<
Sommatino, Yalguanera, and Villarosa, in the province of Galtanisett
Aragona, Casteltermini, Cattolica, Cianciana, Comitini, Favara, Grot^
and Racalmuto in the province of Girgenti ; and Lercava in tiiat |
Palermo. In very rich lands the veins do not average more th^
6j to 27 ft. thick, with sterile strata, from a few inches to 3 ft.
over, intervening ; while in those less productive, the sulphur e
lie separated by barren strata of much greater thickness. The
containing the mineral is detached from &e mass by the use of a e
pointed pickaxe, weighing about 15 lb., and is brought to the moo
of the shaft, which is like an inclined plane running down the ^r
with steep steps roughly cut in the rock, forming, lumoBt invaziaUJ
the only means of access to the works at the bottom of the miiM
The ore is excavated by men, assisted by small gangs of boys workii
under them, who carry heavy pieces of the rock to the snr£iM)e, |
it is broken up by the miners, smd deposit them in localities allutr
to each pickman, where the ore is piled up in large heaps prepar&l
to its being measured, to ascertain the number of *' cassa " ezcavi
by each man. The '* cassa " is the measure by which the qnan
of sulphur ore dug in Sicilian mines is reckoned, when paying
miners for the labour ; but it differs in dimensions in different minii
districts of the island. The boys employed in transporting the mined
carry 40 to 60 lb., according to their ages, which range from 10 to J
years, from pits often over 275 ft. deep, making 20 to 40 journeys
day. Water is frequently met with before reaching a seam of sulpha
and up to the present it has been one of the greatest obstacles in t|
way of mining engineering in Sicily, greatly increasing the ooet \
working. The depth of 190 ft. is rarely obtained without waU
oozing through imperceptible fissures in the rock, and this frequent!
stops all operations by submerging the works.

The richest portions of the deposits are usually found where
beds are arranged in curves^ concave with reference to the overl;
strata, which previously represented the deepest portion of
original lacustrine basinsw Sudden changes, whether of dip or d
tion on the outcrop, are found as a rule to be accompanied wii
impoverishment of the deposits.

The total quantity of sulphur considered as likely to be contain^
in the deposits now known is about 65,000,000 tons, of whici
8,353,091 tons were extracted between 1831 and 1885, or siira
the statistics of production have been kept, and probably aboi^
2,000,000 tons more in times preceding the former date. As the Ioe|
in the reduction of the ore is about one-third, the above quantity i
sulphur sold represents about 15,000,000 tons of material extracw^
which leaves as the stock still to be wrought about 85,000,000 tona

The exact figures of the statistical returns for the sulphur miu*]
of Sicily in 1885 were as follows. Exclusive of the product of (^



Digitized by



Google



NON-METALLIFEROUS MINERALS. 375

olfatara of the volcano in Lipari, 377,132 tons of sulphur were
extracted from 2,548,840 tons of rock, or an averaj^e yield of 14*79
>er cent. The number of hands employed was 28,744, corresponding
o a prodnction of 88J tons of ore, and 13*12 tons of sulphur worth
t3i. 10». for each person engaged in the work.

The oofit of production per ton is made up of the following
terns : —

t. d.

Wages 28 11

Other miniDg and reducing costs 6 10

35 9
Freight to seaboard, warehouse, and shipping charges .. 16



Cost per ton free on Doard 51



9



The annual exports of sulphur from Sicily are about 150,C00 to
70,000 tons.

The sulphur workings at Swoszowice, near Cracow, are in the
uraaeic formation. There are two layers of sulphur-yielding earth,
ach oompoeed of a dark-grey marly clay, through which the sulphur
» distributed in the form of concrete masses, varying in size from
in. diam. to no larger than poppy Bced. These beds are separated
y a vein of fibrous gypum fluctating between 3 and 6 fathoms
bick. The roof is of clay containing petrifactions, and enclosing
Eunps of Bulphur weighing as much as 3j^ lb. The total depth is
bont 30 fathoms. The sulphur yield averages 10 per cent. The
meltiiig of the crude mineral is performed in gallery furnaces, the
ield being approximately GJ per cent. For some years past the
Toduct has been consumed locally for making carbon bisulphide,
rhich is largely employed as a phylloxera cure throughout the grape-
^wing districts of the Austrian empire.

Iceland has been prominently mentioned as a probable large pro-
uoer of snlphur. Prof. Geikie has reported from actual measure-
lents that there are in sight at the Erisuvik mines some 250,000 tons
f sulphur earth (the term ** ore " used by him seems liable to be
xisconstmed), having an average contents of 57 per cent, sulphur.
To commercial success has apparently ever attended the various e£forts
D develop them, and in the opinion of the author, who spent many
lonths attempting to work the Myvatn mines in N. Iceland, the con-
itions do not warrant financial venture.

Japan is exporting about 7000 tons of sulphur per annum, col-
»cted from the sides of an extinct volcano, and yielding about 50 per
BDt. of purity.

The most important deposits of brimstone in the United States
re found in Utah, at Cove Creek, 22 miles from Beaver, while there
fe other deposits at a point about 12 miles south-west from Frisco.

The mines at Cove Creek are said to be in excellent condition for
ontinuous production. A system of storage reservoirs, holding
1,000,000 gaL of water, has been put in, and 6 -in. pipe laid about one
ailo, with a fall of 1000 ft., to carry the water to the sulphur beds, to
mb in hydraulicing the surface earth away. This will greatly re-
l»oe the eost of mining, since there is a large lot of earth overlying



Digitized by



Google



376 ECONOMIC MINING.

the sulphur, whicli in the past had to be dug and carted awaj.
far as explored, the sulphur-bed extends at least 1800 ft. by 1000
and the quantity of sulphur contained therein wan estimAtedj
Prof. Yon Eath, at a time when the bed was not as fully exposed i
now is, to be at least 1,300,000 tons. A curved cut has been n
through the sulphur-bed near its western end, exposing a Tsri
wall of rich yellow sulphur, 34 ft. high. From this cut a track \i
to the dump above the smelter, a short distance to the -west. '
sulphur extends up to the surface over part of the basin, bat is moi
covered with sand or rather decomposed andesite, and is partly mj
with sand or gypsum. Most of it is of yellow colour, while some i
is dark grey, and is called '* black sulphur." The outpnt from tj
mines iu 1891 was 1200 tous.

In Nevada, the Rabbit-hole Springs mines have been woii
irregularly since 1880 ; but the excessive cost of production, trans]
ration, &c., has brought the actual cost at consuming points so t
the sale prices of imported sulphur as to limit mining to an
amounts.

Large deposits of sulphur are known to exist in Wyominff,
fomia, and Arizona, but none of them is at present available
working at a profit.

Extraction, — The separation of the sulphur from the varij
earthy matters with which it is naturallv associated is effected
the following several means: — (1) Dry heat — roasting the ore
mass ; (2) wet heat — ^melting out by the aid of aqueous solutions
salts, the salts being added to heighten the boiling point ; (3) sup
heated steam ; (4j chemical solvents. The great bulk of all \
sulphur produced is extracted by apparatus belonging to the fi
class, and including the calearelle^ calcaroney and doppione.

Calcarelle. — The earliest system adopted in Sicily was the eaJcwi
This consisted simply of a stack of ore, 6-15 ft. square, built iii
ditch 3 or 4 in. deep, with the floor beaten hard and sloped to a siuj
point, permitting the molten sulphur to flow out by an opening t^m
the morto. In building the stack, care was taken to put the largi
pieces of ore at the bottom, selecting lumps of gradually diminish^
size as the top was approached. The mass was ignited at the samnj
The construction of the stack usually occupied two days ; on i
third day the sulphur escaped by the morto, and on the fourth i
edUarelle was pulled down. The air necessary for the combustion
a portion of the sulphur (to afford the heat required to smelt the 1
mainder), was freely admitted at all sides ; only the mineral in t
centre of the heap was heated without actual contact with the air,
that its sulphur was melted out instead of being burned (oxidise^
Consequently about 6700 lb. sulphur mineral were needed to afib
385 lb. sulphur, or a yield of 5*7 per cent. ; as the ore contained I
per cent, sulphur, the consumption of sulphur as fuel was I960 Ih, {
order to extract 885 lb. In addition, the immense volumes of b^
phurous acid emitted from the stack caused a terrible destruotioD I
the agricultural crops in the neighbourhood.

Calcarune. — ^Nearly all the sulphur prepared in Sicily is now e^
traoted by the calcarone (or cmckeroney as it may also be spel^



Digitized by



Google



NON-METALLIFEROUS MINERALS. 377

'his, as is shovirn in Figs. 99, 100, is formed by building a circular
rone wall on an inclined Bole. In front is the morto or outlot, having
height of 4 to 6 ft and a width of 2 ft. ; over it is erected a wooden
lelter for the workman in charge. Calcaroni may contain 200-400
isse (each cassa being equivalent to about 6 tons, and giving 12-16
wt. of sulphur). The durability of the calcarone is governed by the
ire exercised in its construction ; 10 years is not an unusual period.



Fio. 99. — Ordinary Calcarone.



Fio. 100. — Ohdinabt Caloabone.

'he charging of the calcarone is a matter of primary importance, as
n it depends the yield of sulphur. The largest pieces of ore are
elected for the first layer, leaving interstices between them; the
ize of the lumps gradually diminishes as the height increases,
^re being taken to form the walls of the morto with calcareous
tones, so as to ensure a passage being maintained for the escape
f the liquefied sulphur. In adding the finest portions on the top,
arrow channels, about 2 ft. apart, are left for the draught to carry
be heat down. The whole is covered with a layer of the reftibe



Digitized by



Google



378 ECONOMIC MINING.

from previous operations. This layer is more or less thick, acoordinj
to the state of the weather, because the calcarone being built in tb
open air, yariations of temperature and wind influence the progres <
the operation ; consequently means have to be adopted to prevent a
undue access of air rendering the combustion too rapid. For instana
during a sirocco (local hot wind) there is danger of the sulphur coi
tained in the ore lying at the side facing the wind being complete)
converted into sulphurous acid, and thus lost. The employment of
roofed shed would prevent much of the waste occasioned by climati
causes.

When the charging is completed, the morio is closed by a stoo
slab, and fire is communicated to the mass by means of little bundK
of dried herbs, dipped in sulphur, which are thrust into the vertici
channels before mentioned. Some 6 or 8 days afterwards, a hole i
pierced in the top of the morio, by means of an iron rod ; later,
second hole is made near the floor. By these two openings the sol
phur escapes, and is collected in wooden buckets (gravite\ shaped lik
a truncated cone, and holding about 1 cwt. of sulphur. These bucket
cost over 2«., and serve only for 3 or 4 castings without wanting re
pairs. The outflow of sulphur lasts for 2 to 4 weeks. CJommonlj
the calcarone is left to itself when once the mass has been ignited, bn
then the loss of sulphur is much more serious. To ensure good result]
many precautions nave to be observed, mainly connected with th
nice adjustment of the draught, so as to effect the maximum degre
of fusion with a minimum of oxidation. When the operation is ooi^
ducted during winter, the product is less abundant, and of inferio
quality. After the charge is exhausted, a new one cannot be intro
duced till the mass has cooled down, occupying a period of 10 to 9
days, according to the size of the calcarone. The discharging has t
be done slowly and cautiously, on account of the sulphurons fanM
liberated. The consumption of sulphur (as fuel) in the heating i
about 60 per cent, of the total amount contained in the ore. Thus, tj
obtain one ton of sulphur, there is consumed as fuel about anothe
ton, worth, say, 51. and performing a duty which could be much mor
satisfactorily accomplished by 2 cwt. of coal, costing, perhaps, 5$.

A great improvement in the Sicilian calcarone has been introdacet
by P. Le Neve Foster, and worked with good results, shovnng an in
crease of yield of 30 per cent, above the ordinary plan. According U
his description, the waste heat from an ordinary calcaronCy after &I
the sulphur has been run off, is utilised to heat to the required ten^
perature the charge of ore placed in his kiln, and as soon as the mois
ture has been driven off and the heat is great enough, the charge i
fired from the top. The combustion, fed with hot air containing soom
sulphurous acid gas, is very slow, hence the loss of sulphur by bojn
ing is less than when, as in the ordinary calcarone^ the ore has to b
heated entirely by the combustion of the sulphur. The apparsto^
shown in Fig. 101 (prepared from a drawing kindly furnished me l^
the inventor) consists essentially of three parts : — (!) the flue, or o(fflj
ductor of heat; (2) the kiln, in which the ore is treated; (3) tk
chamber for the condeubation of the sulphur that is volatilised doling
the fusion, and in which it is collected.



Digitized by



Google



NON-METALLIFEROUS MINERALS. 379

The kiln may be of any suitable form to contain two obargee of
re, bat a rectangular chamber is found to be most convenient, with
uor alopiDg towards the front. The chamber consists of four walls,
referablj not covered with an arch, as afifording greater facility for
barging and discharging. The kiln communicates by means of a
oe a with the back of an ordinary calcarone 6, which furnishes the
eat necessary for melting the sulphur from the ore contained in
tie kiln c. The upper portion of the ccdcarone should be covered with
hjtr of genese (spent ore), so as to prevent the dispersion of heat
J auy other channel than that o£fered by the flue a, which is provided
rith a damper c{, so as to regulate the admission of heated air by
penings e, at the upper back part of the kiln. A rectangular open-
ig / is left in the front wall of the kiln, from which the melted



Fig. 101.— Fo8tbb*8 Impboyed Caloabons.

ilphur is run. This opening, if of suflSoient size, may serve for dis-
^ging the spent ore at the termination of the fusion. From the
pper part of uie opening, and also in the front wall, slightly above
ke level of the floor, flues g communicate with a horizontal passage

which is made large enough to serve as a condensation chamber, on
16 walls of which the sublimed sulphur collects. At one end of the
lamber is a vertical chimney t, provided with a damper k.

The kiln is charged in the usual way by placing the large pieces
' ore on the floor in such a manner as to leave passages for the flow

the liquid sulphur ; the small pieces are next filled in, and the
ler ore at the top. A few blocks of rough stone, or burnt ore, are
laced at the opening in front in such a way as to leave a vacant
lace for the melted sulphur to collect before being run off. When
barged, the ore is oovered with bricks laid flat, and on these is put
layer of genese^ well rammed and wetted, so as to form a nearly im-
irmeable coating, with a slight slope towards the walls, in order
lat the rain water may run off. The opening / in the front wall
|onld be closed with a thin wall of plaster of Paris. The ore in the
ihi, which is now ready for fusion, is put in communication with
ie spent eaUarcne 6, by opening the damper d, and at the same time a
Ball hole m is made in the wall that closes the opening in front,
em which the melted sulphur has been run off from the calcarone 6.
he corrent of air entering and passing through the incandescent



Digitized by



Google



38o ECONOMIC MINING.

mass of ore, is thnn heated, and enters the kiln at a sufficient tempera
ture. In this manner the heated mass of spent ore in the calcarm^
becomes a regenerator of heat, to be utilised in the kiln for the fi
of the sulphur that it contains. In the upper covering, two or
tubes n are placed, and serve not only for observing the rn^
temperature by a thermometer, but also for firing the ma^.

The combustion of the sulphur supplied with hot air, mixed wit!
a considerable proportion of sulphurous acid gas, proceeds slowly i
the upper part of the kiln, and the liquid sulphur dropping to thj
floor, over the already heated ore, cannot solidify and choke the pa*
sages, and so prevent the circulation of the heated air and product
of combustion of the sulphur to the chimney ; in this manner thj
operation proceeds with regularity. The success of the kiln is pnn
cipally due to the manner in which it is heated from the top and b&<^
towards the front and bottom, imitating, to a certain de^cree, tb
manner in which the heating of an ordinnry calcarone proceeds, ^it]
this di£ference, that the heat is better utilised in the kiln, and, ther^



Online LibraryCharles George Warnford LockEconomic mining: a practical handbook for the miner, the metallurgist and ... → online text (page 42 of 76)