Charles George Warnford Lock.

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

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Per cent. Per cent.

41 15 or Sodium carbonate (Na,CO,) .. 46*90

38-94 „ Sodium bicarbonate (NaHOO,) 37-17

19-91 „ Water (HjO) 15-93



From this we derive the formula Na2C08+NaHC03+2H20, which
M long been known under the mineral name of " urao," or " summer
da/' its name at Ragtown.

The amount of this salt thus obtainfd will depend upon the
-oportion of bicarbonate present, as every 37 '17 parts will in
y stalliaing take with it 46 * 9 parts of Na^COj. If more than suffi-
snt bicarbonate was originally present, the excess will crystallise
tt before any ** summer soda" forms. If too little is present, the
:ct» of carbonate remains in solution.

On evaporating a sample of water from any of the lakes, at a
rtain oonoentration point (sp. gr. 1*260 for Owens Lake water)
ystallisation will begin. The crystals are crude summer soda.
wing to the presence of so much sulphate and chloride in the
Intion, the crop becomes more an^ more contaminated with these
lis as the concentration proceeds. Hence to obtain an article of a

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354 ECONOMIC MINING.

fair degree of pnrity the prooess must be interrupted at some d^ite
degree of specific gravity, and the mother liquor be drawn off. If th«
mother liquor be nirther evaporated, successive crops can be obtaiDed,
the earlier ones, in the case of Owens Lake, being prindpally
sulphate, and the later ones chloride ; while finally we get a moth«r
liquor rich in potash salts, from which, on cooling to a low
temperature, the ordinary "soda crystal" (NajCOj+lOHjO) ii
deposited.

While all these localities can produce summer soda in the manner
described, none has enough bicarbonate in its water to give ti»
largest possible yield. It is necessary to increase the proportion of
bicarbonate, which can be done in several wavs, but most economi-
cally, perhaps, by utilising the carbonic acid given off in the prooea
of ^macing the summer soda, 'i'his, when heated to a modenfe
degree, loses its water and excess of carbonic acid, 100 parts yielding
70-36 parts "ash," 9-74 parts gas, and 19-91 parts water. Tla
fumacing must be done in any event to reduce weight and Bare
transportation charges ; hence, if the gas can be economically used,
there is a clear gain.

At present all the product is shipped in its crude condition ffl
borax works in the vicinity, where it meets with a ready sale i1
remunerative prices. The present annual output is given as book
2500 tons, while the Kagtown works produce about 800 tons. TTn
cost is sufficiently low to warrant the assertion that there are sevend
places at which ash of vet"^ satisfactory quality can be made at a ooil
not exceeding 12. per ton.

The manufacture of high-grade soda-ash and other products frofl
the natural material divides itself into two stages, each perfect^
distinct from the other.

1. Field work, including vat construction and arrangement^ pump
ing and handling of the original solutions and the mother liquoi^
control of the crystallisation process, gathering of the summer sodi
and transportation of it to the refinery.

2. Befining work, in which the summer soda is put into vari<nl
marketable forms and delivered to the consumer.

The field work is dependent for its conduct and economy oi
climatic conditions. These, while most favourable for evapoiatioi
and crystallisation, produce a scarcity and consequent high cost i
manual labour. The amount of this must therefore be reduced to i
minimum and be supplemented by machinery. The use of the lat^
when steam driven, is limited by the fuel cost, which will always h
high. Windmills can be used for pumping, and simplicity of arrange
ment and various mechanical devices can greatly increase «l
efficiency of the workmen, particularly in gathering the crop. If fl
a large plant the vats are properly arranged, accurate control will h
made easier and the transportation cost reduced to a minimum by ^
use of light railways.

The field work can be done on a large or a small scale with pio
bably equal advantage. At the Little Lake at Bagtown in 1886 X9i
men made 300 tons, and could have done much more had the oonditkafl
of the locality permitted it. The product of the Big Lake, otfii



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NON-METALLIFEROUS MINERALS. 355

nder very adverse conditions, required but little more labour in
roportioD. The entire product is hauled 16 miles to the railroad
Dd shipped to San Francisco, where it is refined.

Fornacing before shipping to the refinery is not always advan-
igeoQs. True, the reduction in weight is about 25 per cent., but the
iving in transportation will rarely pay for the cost of fumacing
rben this is done on a small scale. Moreover, refiners will prefer
nfQiTuioed material, and by devoting attention exclusively to the
rodnction of summer soda, regularity in composition, which is very
oportant, can be better assured.

During the dry season, the surface of the land in many parts of
forth China is covered with a white incrustation of salts, called c^ten
jr the natives, which easily dissolves in water, and therefore disappears
aring the rainy season. A sample collected in the neighbourhood of
fckin, a few 1% to the south-west of the city, contained : —

Per cent

Chloride of Bodium (common salt) 23-8

Carbonate of sodium (soda) 12-4

Sulphate of sodium (Glauber's salts) 63*8

100-0

Large quantities of these salts may be obtained by having the
round swept with a broom and lixiviating the sweepings with warm
ater. Over a third of the material thus collected proves to be soluble
fttter. It may be separated from the solid residue either by filtering
' hy siphoning the supernatant liquor and evaporating the saline
btion, which shows a strong alkaliue reaction on account of the
rhonate of sodium contained in it. When su£Sciently concentrated,
« liquid, on cooling, deposits a large mass of crystalline matter,
hich mostly consists of sodium sulphate, a part of it, together with
e sodium carbonate and chloride remaining in the mother liquor.
be latter, on being evaporated, yields a brownish looking substance —
e colour being due to organic matter — which, on being treated with
oegar, shows a brisk effervescence. It is to all intents and purposes
e same substance as the one called izu-cliim by the Chinese, which
&n impure carbonate of soda extensively used in dye works. Not
ily does it serve for the cleansing of textile fabrics, but, owing to
> Urge amount of sodium sulphate, is also used as a mordant, for
stance, in colouring cotton cloth with a solution of indigo, &c.



Colour.


Water.


Qu-b.

Sod*.


Chloride
Soditim.


Snlphate
Sodium.


Com.


oQ-diien (from Ka]gan>—
1. Fien ohien, yeUowisb, white

B-k*<m ebien (from Sbansi)—
1 Pai cbien, white

3. Tto cbien. first <juality, dirty yellow

4. Do. second quality, brown ..


per cent.
45-61

52-60
28-65
17-30


percent.
53-00

45-71
41-61
33-13


percent
1-33

1-07

6-29

18-14


traces

traces
23-46
31-27


dec.
31-41

27-09
24-66
19-19



Judging from the above, there appears to be an abundance of
dium sulphate in some parts of China which may become valuable

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356

when, with the I

factnre of glass i . . „

The table below gives an analyslH of each of the four kinds of sq
distinguished in trade. The samples were obtained from one of i
great depots outside the city. For q^mparisoii, the Ciigliish co
inercial ** degrees " have be^-n added.

At present this substauoe is extensively used by the Chinese
cleaning purposes, taking the place of soap in foreign couu tries.



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NON-METALLIFEROUS MINERALS. 357



STONE.

HE tenn stone is here used generically and embraces such widely
iferent snbHtanoes as marbles, slates, lithographic stones, &c., which,
K)ugh applied to divergent purposes, are yet similar in origin and
ioe^ much in the same manner.

Building Stones, — Perhaps at once the commonest and the most
Befol kinds of stone are those employed in constmction. Geologically
ley oover a very wide range, and it may almost be said that no
sriod is devoid of beds or deposits of mineral adapted to the mason's

Of far greater importance than their geological horizon is the
icroscopic structure of stones to be used for building purposes, and
reat loss and disappointment have followed inattention to these
itares. But while incipient decay may thus be detected, it is not
ways safe to assume that because a rock contains a mineral that has
ready commenced to decompose, as shown by examination under the
icroecope, therefore this stone is valueless. Occasionally microscopic
ides of sandstones will show that the felspar has commenced to
kolinise, but that the decay has been arrested. The decomposition
idonbtedly took place in such sandstones (of Triassic origin) previous
the degradation of the rocks which now compose them. When these
ere ground up, and their elements redistributed to form the sand-
one, there seems to have been a cessation of the causes which pro-
loed the decomposition; this was arrested, and has not since
Ivancdd any further in the rock.

The characters which it is important to observe,* are whether the
Dne contains minerals which are either already decomposed, or are
cely to become so ; whether these minerals contain water in cavities

ooDsiderable quantities ; or whether, either by disintegration or by
e locfseness of the binding material, the stone contains so many
teistices or fissures that it is likely to absorb large amounts of
Iter, which may either attack certain of the constituents, causing
em to swell, or may itself, under the influence of a severe climate,
tve sufficient power, in the form of ice, to disintegrate the stone.
^6 examination of the stone in the quarry should be conducted as a
bole, and not with reference to a particular part of it, for it not
ifrequently happens that stones composed of exactly the same
iuerals have entirely di iferent properties, as granite and gneiss, for
^unple, and yet one of them may not be a proper stone for outside
nstmction. The age of the stone, since its extraction from the
umy, may or may not be in its favour. Nearly all stones are weaker
imediately after their extraction, while they hold the quarry water,
^ after they have lost it. Most stones after lung exposure, more

♦ T. Egleston, * Building Stones.'



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3S8 ECONOMIC MINING,

especially if they have not been uniformly moist, absorb more w«to
than when they are fresh, and are therefore more likely to disint^^nl
from frost than when they were yonnger, or than if they were ke|
uniformly moist. Certain rocks, exposed to high heat or to seTei
cold, lose their power of resistance along irregnlar lines of weaknes
and tend to disintegrate, and this effect may 1^ produced by artifidi
heating as well as by climate. Stones, therefore, which endure ei
ceedingly well in one climate may not stand in another. Tl
particular places where the structure is to be erected, whether in d
city or country, is to be considered. In the city there are noxiw
and corroding gases, coming either from fuels or manufactories ; tl
dryness or dampness of the ground is to be cousidered, and whetb
the particular spot chosen is well ventilated or not ; in the countr
whether the air is humid or dry, or whether there are prevailing bi|
winds cariying sand. All these, and manv other circumstances, hat
great influence on the durability of building stones, and should I
carefully considered before expensive structures are undertaken.

Building stones may be divided into three general classes : fin
the different varieties of granite and granitic rocks; second, tl
marbles, which may have a coarse or granular structure, and may 1
either Umestone or dolomite or serpentine; third, the sandstoD<
which may be composed of material having an organic, an argillaceon
a ferruginous, a calcareous or a silicious binding material Slates «l
occasionally used in building, but not frequency. They are subj^
to peculiar forms of decomposition when they are used as room
material, about which little need be said, because the deoompositii
which they would undergo in such very thin sheets would hardly ta)
place when they are used in thick pieces in the construction of i
ordinary building. Besides these stones, there are a few others whii
are sometimes used in the vicinity where they are found, such
various kinds of trap or basalt and serpentines ; also steatites, al
some other very soft rocks. Their use, however, is not oommc
Each of these stones is subject to its own particular kind of dec^
which may be either chemical or mechanical.

All stones, and sandstones especially, contain, when freshly brok
from the quarry bed, varving amounts of moisture, or quarry wat4
as it is technically called. If exposed to freezing while in this cd
dition, they are, if not actually burst and ruined, at least rendexi
less tenacious. In many localities it is necessary to flood t^e quan^
with water, or cover them with earth, on the approach of cold weathi
to prevent serious damage from this cause.

Experiments made on a number of building stones after freeeh
and thawing 25 times, showed only six samples which possessed f4
resistance to such treatment ; they included a dolerite, a diorite, a]
four sandstones. Eesistanoe to fire and to water applied during gn
heat are every day becoming more important considerations in
building stone, and in these respects the volcanic rocks and the san
stones, when of homogeneous structure, are preferable.

Dolomite (the double carbonate of lime and magnesia\ often calli
magnesian limestone, is of uncertain composition, rarely pres^itii
the true proportions of 54*35 lime carbonate and 45*t>5 magnei

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NON'METALLIFEROUS MINERALS. 359

ctrbonate. As a building stone its qualities vary exceedingly. A
nlidous variety is used with great suocees in the north of England,
but the Houses of Parliament bear testimony to a total £eiilure of
inother kind to withstand London air.

Limestone proper is well illustrated by the world-renowned Bath
hsestone, a famous warm-toned stone, which possesses the remarkable
)Tialitie6 of durability and easy working at the same time, ^he beds
a Bath stone are contained in the formation known as the Qreat or
Bath Oolite.

Although, in accordance with geological investigation and deduc-
ions, Bath stone should extend over a considerable area, this is found,
n practice, not to be the case, the area being a tract about 30 miles
ong and 10 miles wide, extending to the east of Bath between
Chippenham on the north and Trowbridge on the south. But even
a this limited area the stone has only been found at a workable depth
D certain localities, though innumerable bore holes and trial shafts
lave been put down to prove the ground. Moreover, the beds, though
wind almost horizontal where worked, vary greatly, within short
istances, from one unbroken stratum averaging 7 ft. thick, to several
b^ta measuring, together, 21 ft. The quality also differs in the
sveral localities, which yield stone adapted to various usages.

The system of quarrying or mining here employed is described
elow. An average sample of the stone is of 2 * 2 sp. gr. when dry,
00 lb. of stone absorbing only 9 lb. of water ; and in actual practice
. will stand a pressure of 70 tons per sq. ft. without cracking.
Aslysis shows: — Carbonate of lime, 97-2; alumina and iron oxide,
'6 ; silica, 1 ; magnesia carbonate, '2. Its selling price is 11(2. per
iKft.

Marble is generally understood to be carbonate of lime, either
hite or coloured, uniform or variegated, and pleasing to the eye ;
Le term is also applied to any coloured stone soft enough to easily
it, and hard enough to bear a good polish.

True marble is lime carbonate, composed of carbonic acid and the
:ide of calcium, or lime, in the following proportions: — Carbonic
•id, 44 ; lime, 66.

Of all the ornamental and decorative stones, the marbles are the
aet abundant and varied, and at the same time the most extensively
a ployed. Any rock susceptible of a fine polish is termed ^' marble "
r the stcpi^-cutter ; hence we hear of " Connemara marble," which is
roe serpentine ; and of ^ Sicilian marble," which is often a brecciated
va. The term, however, should be, and is, restricted by geologists
limestones capable of receiving a polish, and frequently exhibiting a
kiiety of colours in veins and blotches. We have thus uni-KK>loured
^rbles, such as pure blacks and whites ; and party-coloured sorts,
triving their tints from accidental minerals, from metallic oxides,
ving them a veined or clouded appearance, or from shells, encrinites,
rals, and other organisms which impart a variety of figure as well

of hue. Every country has its own peculiar marbles. These
txieties are almost endless, but the following are a few of the better
kx>wn and more esteemed varieties, ancient and modern. Carrara r
ire white, saocharoid, and semi-transparent; highly esteemed for



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36o ECONOMIC MINING.

statuaiy purposes; 98*1 per cent, lime carbonate. Parian: of a
waxy cream-colour, also crystalline, and employed in statnarj.
GiaUo antico : yellow, and mixed with a small proportion of inm
hydrate; used for ornamental purposes. Sienna: rich yellowish-
brown, with lighter veins and cloudings. Bosso antico : deep blood>
red, less or more veined. Mandelato : light red, veined and clouded.
Verde aiitique : cloudy green, mixed with serpentine, or serpentise
itself. Cipolino : a mixture of talcose schist with white saocharoidil
marble. Bardiglia : a bluish-grey variety, with bold black veins and
cloudings. Lumaohello or fire-murble : a dark-brown variety, having
brilliant chatoyant reflections, which it owes to the nacreous matter
of enclosed shells. Black marbles : like those of Derbyshire, Dent,
and Kilkenny, deriving their dark colours from bitumen. EncriiiAl
marbles: like those of Dent in Yorkshire and other Carboniferoiia
districts, deriving their " figure " from the stems and joints of eo-
crinites. Shell marbles : like those of Purbeck and FetworUi in
Dorset and Sussex, and Eingsbams in Fife, receiving their ^figure*
from the component shells of univalves and bivalves. NununuH^
or Verona: creamy to nearly white. Phrygian or pavonazetta : cA»mj
white ground, veined with dark red, pink, or yellow. Equal in bean^
to any of the ancient marbles, and surpassing most of them, is tba
onyx now being mined in Mexico, New Mexico, and Arizona. It
weighs about 200 lb. per cub. ft., and can be cut out in blocks of asv
desirable size, up to 20 ft. by 10 ft. ; it is worth 50«. per cub. f L at tb«
quarries.

The mode of working the underground stone quarries near B&tli,
above alluded to, is somewhat peculiar, and is thus briefly deocnbei
by Prof. C. Le Neve Foster.

The dip of the beds is slight, being only 1 in 33. The bed o£
stone which it is proposed to work is reached by an inclined pknor
and then a main heading is driven out, 15 or 16 ft. wide, with ^'iide
holes " at right angles as wide as the roof or ceiling will admit witk
safety, say 20-24 ft., leaving pillars 10 ft. square and upwards. H
rock is unsound, it is left as a pillar, and this may cause so
irregularity in the plckn of the mine.

The first process in removing the stone consists in excavating
the '^ jad," a horizontal groove at the top of the bed, which is cot is
for a depth of 5 ft. and width of 20-25 ft. The jad is cut out with i
pick, which is not set quite at right angles to the hilt. This fon
enables the workman to cut right into uie comers. The first pick
weighs 7 lb., the second 6 lb., and the third 5 lb. This last has a hill
5 ft. long, so that the man may cut the jad to a' full depth. Projecting
pieces of roof are broken down by the *' jadding iron," a long bar.
After the jad has been excavated with the pick, two vertical cuts an
made with a saw, and a piece, called the " wrist," is wedged up froa
the bottom or off from the side. When the " wrist" has been removed,
the blocks are simply cut out with saws. These saws are 6-8 ft. loo|,
by 10-12 in. wide. The first saw used in the jad has to be narrower,
and is called the '* razor saw." The heaviest saw weighs 56 lb., vA
the handle can be used entirely below the eye when working satf
the roof.



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NON-METALLIFEROUS MINERALS, 361

WheD set free by sawing on all four sides, the block can easily be
letached by wedges driven in along a plane of bedding. The blocks
ire lifted off by cranes, and either loaded at once on to trucks, or
tacked inside ^e quarry, after having been roughly dressed with an
ixe or with a saw. A workman can saw 15 sq. ft. of the softest beds
u hour. The men work in gangs, and the ganger is paid at a certain
ate per cub. ft of stone delivered on the trolleys at his crane. The
sen make from 20«. to 28«. a week; the ordinary hours are from

A jf. to 5 P.M., with two hours for meals. Good pickers cutting out
he jad can earn as much as 1«. per hour while at work, but at this
ate they wiU not work more than 5 or 6 hours a day. Owing to
ilse bedding and other irregularities, a bed of stone 20 ft. thick will
aly yield on an average one-half of blocks fit for the market.

Ever since blasting has been imed in quarrying, efforts have been
lade to direct the blast so as to save stock. Holes drilled by hand
re seldom round. TUe shape of the bit and the irregular rotation
hile drilling usually produce a hole with a triangular section. It
r&s observed, many years ago that, when a blast was fired in a hand
rilled hole, the rock usually broke in three directions radiating from
le points of the triangle in the hole. This led quarrymen to look
tr a means by which the hole might be shaped in accordance with
prescribed direction of cleavage.

A system used successfully for a number of years comprises the
rilling of deep holes 10 to 12 in. diam., and charging them with
cploeives placed in a lune-shaped canister made of two pieces of
leet tin, with sections, minor segments of a circle, soldered together,
kd the ends filled with cloth or paper. Earth or sand is filled in
ound the canister in the drill-hole, so that the effects of the blasts
e practically the same as though the hole was drilled in the shape

the canister. Straight and true breaks are made, although the
stem is expensive, as obviously a larger hole than necessary is
iUed.

Another of the older systems of blasting is that known as lewising.
RTo or three holes are drilled close together on parallel, the partitions
tween being broken down. Thus a wide hole or groove is formed,
to which the powder is charged by being rammed down, or in a
1 canister the shape of the trench-hole. This system is confined
nost entirely to granite. Then, again, there is the well-known
ag and feather system, in which the plugs are driven between the
kthers by the blast, and the rock is split. This process frequently
sultB in irregular breaks and damage at the top of the hole.

By the Knox system a round hole is drilled by hand or otherwise,
eferably by a machine drill, €U9 it is important that the hole should
leed be round. In sandstone of medium hardness these holes may
situated 10, 12, or 15 ft. apart. Then the holes should be reamed
t with an instrument made for that purpose, at least 1^ times the
kmeter of the hole. This is done to the bottom of tiie hole. When
ished, the hole resembles the shape of the canister. I'hen the
le is charged with the smallest possible amount of slow-acting
wder; dynamite is unsuitable. The cap should be inserted near
^ bottom of the cartridge. Then the tampitig is put in, not



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362 ECONOMIC MINING.

directly upon the charge, as in most systems, but an air-space is k
between. The tamping should be placed about 6 to 10 in. below t]
top of the hole, and placed securely so that it will not blow oi
The intervening air-space may be tilled with a wad of hay, grat
or paper. The hole is now ready to blast. If several holea are on
line they should be blasted simultaneously by electricity. The ^St
of the blast is to make a vertical seam cocnecting the holes, u
the entire mass is sheared several inches or more. The explaoalii
of the rationale of the blast is that the gas, acting equally in i
directions from the centre, is forced into the two opposite wedg
shaped spaces by a force equally prompt and energetic. All rocl
possess tne property of elasticity to greater or less degree, and tb
principle being excited to the point of rupture at the apioee of tl



Online LibraryCharles George Warnford LockEconomic mining: a practical handbook for the miner, the metallurgist and ... → online text (page 40 of 76)