SULPHUR.— Compounds.
one terziaria nella zona solfifera della Sicilia,” “ Me-morie del R. Comitato Geologico d’ Italia,” vol. i.,1871. Fig .. 3 is a cross - section of La CrastaSulphur Mine near Delia, copied from Mottura’swork, and shows how the seam of sulphur lies:
a, ferruginous marls and clays (Lower Miocene) ;
b, siliceous limestone (Upper Miocene) ; c.. sulphurseam, decomposed into briscale at the outcrop;d, gypseous and bituminous marls; e, marly lime-stone with foraminifera.
In the Romagna there are some large and impor-tant mines near the town of Cesena. The geologicalhorizon is the same as that of the Sicilian sulphur.There is a bed of limestone about 10 feet thick, partor the whole of which is sulphur-bearing. Theaccompanying section (Fig. 4), showing the rocksnear the sulphur seam in one of the Boratella mines,gives a good general idea of the mode of occurrence.
At Radoboi, in Croatia , “ the sulphur is inter-calated in beds full of remains of insects and plants,and coloured brown by mineral resin and carbona-ceous matter” (“Manual of Geology:” Jukes andGeikie, 1872, p. 55). At Swoszowice, in Galicia ,the sulphur is found irregularly deposited in nestsin shale, interbedded and veined with gypsum, andis worked at three horizons. The sulphur ore yieldsabout 10 per cent, of sulphur (“Denkbuch desOsterreichischen Berg und Hiittenwesens,” Vienna ,1873, p. 261).
Sulphur Mining .-—In Sicily the sulphur seams areusually reached by means of inclined shafts, at anglesof from 30° to 50°, which the miners ascend by stepscut in the rocks. The miners then drive out galleries5 or 6 yards apart down the dip, and then galleriesalong the strike, leaving pillars 5 or 6 yards square.The galleries are 6 to 8 feet wide. The pillars arethen gradually worked away, the roof being allowedto fall in. When there are two beds, one abovethe other, the pillars are supposed to be left oneabove the other; but from absence of plans, it veryoften happens that a pillar has a very unsafe footing.In many cases, however, especially where there arevery thick deposits, the workings are most irregular;galleries are driven out in all directions, hugecaverns of all shapes and sizes are excavated, andare kept up by an occasional small pillar, whichoften rests on the roof of a cavern underneath. Theconsequence is that after a time the workings fall in.The miners then make a fresh start somewhere else ;and after a time, when they think the ground hasgot settled, go back into the old workings, drivingin levels, which are secured by masonry all round.They then extract as much sulphur as they can.
The sulphur rock is worked away partly by thepick and partly by blasting. The state of mining inSicily is so primitive that the ore is generally carriedalong the levels and up the shafts on the backs ofboys and lads. The mines are drained by aditlevels, hand pumps, and rarely by pumps driven bysteam engines.
In the Romagna the system of mining is notso rude as in Sicily . At the Boratella mine, forinstance, they sink shafts till they reach the seam,
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drive out levels, and then take away the sulphurseam, leaving pillars, 10 or 12 feet square, at dis-tances of about 24 feet apart; the pillars graduallycrumble away, and the roof falls. The mineral isconveyed underground by wheel-barrows and tram-ways, and is raised to the surface by horse-whims,or winding apparatus driven by a steam engine.The mines are worked at a depth of from 60 to 70fathoms. When sulphur is worked in solfataras,the earth is simply dug up.
Natural Compounds of Sulphur. — Sulphurettedhydrogen is given off from volcanoes and solfataras,some mineral springs, such as the well-known oneat Harrogate, and is found in the. air of sulphurmines and in some coal mines. Sulphides of themetals of the alkalies and alkaline earths are alsoconstituents of some mineral waters—such as thoseof Aix-la-Chapelle, Aix in Savoy, Saint Boils, nearDax, and Bex, in Switzerland —which afford evidenceof the deposition of sulphur from aqueous solutions(“ Manual of Geology,” Jukes and Geikie, 1872,p. 55).
The sulphides of the heavier metals are so nume-rous that it will be impossible in the limits of thisarticle to enumerate more than a few of them.
Iron pyrites, FeS 2 , crystallizes in the cubicalsystem ; colour, between a brass-yellow and a gold-yellow. It is a mineral very largely diffused innature, and occurs in a great variety of rocks ofall ages.
Marcasite has the same chemical composition asiron pyrites, but crystallizes in the rhombic system,and has a much lighter colour. Like iron pyrites,it is used for making sulphur, sulphuric acid, greenvitriol, and alum.
Pyrrhotine, or magnetic iron pyrites, Fe^Sg, hasa peculiar bronze colour. It is sometimes importantns containing a few per cent, of nickel.
Mispickel, FcAs + FeS„ is useful as a source ofarsenic.
Among other important sulphides which constitutevaluable ores of the respective metals are Zinc-blende , ZnS ; Copper - glance, Cu 2 S ; Bornite,3Cu 2 S + Fe 2 S ;J ; Copper-pyrites, Cu 2 S + Fe 2 S s ;Galena, PbS ; Cinnabar , IlgS.
Silver-glance is a sulphide of silver, Ag 2 S, andthere are numerous sulpho-arsenides and sulpho-antimonides of silver—such as proustite, pyrargyrite,stephanite, and polybasite.
Sulphur occurs also in nature in sulphates. Inmineral springs, for instance, there are sulphates ofthe alkalies, such as sodium sulphate. The sulphatesof the metals of the alkaline earths are widely dis-tributed. Barytes, or barium sulphate, is very commonin mineral veins ; gypsum, CaS0 4 + 2II 3 0, is foundin large quantities in sedimentary rocks. The seaforms a vast reservoir of sulphates, containing, asit does, 0T62, or, roughly speaking, one-sixth, percent, of gypsum, and 0T97 or nearly one-fifthper cent, of sulphate of magnesium (Epsom salt ).Natural alums, or hydrated double sulphates ofaluminium, and another metal—such as potassium,sodium, magnesium, or iron—are also met with.