VEIN. 



in ore on one fide of the fiucan, will be poor on the other 

 fide. This faft, which we beheve has not been fufficiently 

 noticed, is well deferving attention, and would indicate that 

 the prefence of water affefted the contents of veins. 



Some veins' contain little diverfity in the nature of their 

 contents, being filled principally with one kind of ore or 

 vein-ftone. Other veins contain a great variety of minerals, 

 without any apparent regularity of arrangement : there are 

 alfo numerous veins which have a regular ftrufture, the dif- 

 ferent minerals being arranged in parallel layers, coating 

 each other : the fame fucceffion of different minerals occur 

 on each fide and meet in the middle, filling up the vein, or 

 fometimes leaving an empty fpace between. Thus calca- 

 reous fpar, fluor fpar, barytic fpar, lead-ore, blende, and 

 grey copper-ore, form different layers over each other in the 

 fame fucceflion on each fide of the vein. In the Botallock 

 mine, before defcribed, copper-ore is frequently fousd lin- 

 ing each fide of the vein, and this is covered by tin ; but 

 in other parts of the mine the tin covers the walls, and is 

 fucceeded by copper. 



Irregular J^e'ms. — Befides rake-veins, which may be confi- 

 dered as regular, there arc other veins which prefent a great va- 

 riety of ftrufture, and are called bi'Uit's, pipes, &c. according 

 to their form. If a rake-vein be regarded as a tubular mafs of 

 mineral matter interfcfting mountains ; if this vein become 

 irregulai-, and have its fides clofed, or, as the miners call, 

 twitched in, it forms what they denominate a pipe-vein, or 

 mafs of ore and vein-ftone fometimes of a tubular fhape, de- 

 fcending to a confiderable diftance like a pipe. In other 

 inftances, the fides are clofed in both above and below, as 

 well as on the fides, inclofing what the miners call a bel/y, or 

 mafs of ore of confiderable magnitude. Sometimes a fmall 

 rib of ore is continued through that part of the reck where 

 the fides of the vein are twitched in, until the vein expands 

 again and produces another mafs of ore. In fome inftances 

 there is no ore between, a rib of vein-ftone or rider of 

 clay being carried through the narrow part or tiuitch of the 

 vein, but many of thefe twitches contain neither ore, clay, 

 nor rider. In fuch cafes, it becomes exceedingly difficult 

 to follow the vein through the rock, to where it opens out 

 again. 



The veins in general do not clofe fuddenly, but the fides 

 gradually approach each other, and the ore terminates in the 

 form of a wedge at the twitch. 



Thefe contraflions or twitches are of various lengths, and 

 no miner can tell, when the vein is fo fqueezed in, how 

 many fathoms he muft pafs through before it opens again, 

 unlefs the fame twitch has before been cut through above 

 or below the part where he is working. The intervening 

 fpace between two maffes of ore is called a bar, and fome- 

 timesiextends ten, twenty, or even a hundred fathoms or 

 more ; and when it is cut through, the ore makes its ap- 

 pearance, and begins gradually to widen and form another 

 mafs or belly. When one of thefe bellies of ore proves 

 pure and folid, it generally happens that all the contiguous 

 bellies prove fo in the fame vein. According to Mr. Forftcr, 

 inftances have been known of eight hundred tings of ore 

 being raifed by fix miners from one of thefe bellies in the 

 fpace of nine weeks. 



When the matrix in thefe large bellies of ore is foft, the 

 ore is generally found in a globular form, more or lefs irre- 

 gularly imbedded in the foft materials, and thefe globular 

 maffes of ore are of various dimenfions. It is no uncommon 

 thing to find the foft openings in this kind of vein fwell to 

 an enormous width, fo as to make it difficult to find the 

 real fides of the vein. Working thefe veins is the moft^ 

 difficult part of mining, as there is no proceeding a foot 



without advancing timbers as far as they go, in the form of 

 a paffage in a houfe, compofed of two fide-poile, a lintel 

 and a fole. The miners ftand within this fquare frame, 

 where they work and ereft more timber as they proceed. 

 It frequently happens that the ore is fo plentiful and rich in 

 this kind of metallic repofitory, as abundantly to compen- 

 fate for all the labour and expence. 



Flat Feins and Beds. — When a vein runs parallel with the 

 ftrata, it is called a flat vein. If the ftrata are foft, and the 

 metallic matter is widely diftributed, fuch veins do not differ 

 from beds, being regular beds or ftrata impregnated with 

 metallic matter. When flat veins run between hard ftrata, 

 they are alfo hable to contraftions, or ttvitches, and again ex- 

 pand, forming pipes or tubulai- maffes of ore, which extend 

 in an inclined pofition, having the fame dip as the ftrata. 

 Flat veins may be diftingnilhed from beds by this charac- 

 ter ; proper flat veins appe.ar to be openings between the 

 ftrata which have been filled with metallic matter from a 

 rake-vein, or are at leaft connected with it, as they feldom 

 are produftive of ore, except in the vicinity of the vein ; 

 whereas beds are regular ftrata, having the fame elevations 

 and depreffions as the other ftrata in a mountain, but con- 

 taining metallic matter more or lefs abundantly fcattered 

 through them. Iron ores and ores of manganefe frequently 

 occur in beds, forming regular parts or layers of the moun- 

 tain. Other metallic ores, which occur lefs frequently and 

 abundantly in beds, are, we believe, for the moft part veins 

 which have taken the courfe of the fofter beds and diftri- 

 buted their contents through them. It is well known, that 

 when a vein defcends through ftrata of different kinds of 

 rock, it grows wider in the foft ftrata, and contracts in the 

 harder beds of rock. 



The metalliferous beds in Cumberland appear, in many 

 inftances, to be foft beds, rendered produftive of ore by a 

 number of fmall veins running through them. There are 

 few metallic beds in England, except in that county. Man- 

 ganefe occurs in beds in red fand-ftone ip the vicinity of 

 Exeter, but the metallic matter decreafes as the beds dip 

 from the furface. Metallic beds, in primary countries, oc- 

 cur moft frequently among the fchiftofe mountains, com- 

 pofed of gneifs, mica-flate, and flate. ( See RoCK. ) It is 

 obferved, that the ores and minerals which occur in beds 

 are feldom cryftallized, as thefe beds contain few drufes or 

 cavities to admit t"he formation of cryftals. The minerals 

 in beds are accompanied with garnet, aftinolite, and horn- 

 blende, which never occur in rake-veins. See Garnet, &c. 

 Stock-nvorke. — When a rock is croffed and penetrated by 

 a great number of fmall veins in every direftion,. the whole 

 mafs is worked as an ore, and is called by the Germans a 

 ftock-worke, or werke, the rock being afterwards feparated 

 from the ore by pounding and wafliing, in the fame manner 

 as the vein-ftone is cleared from the ore in other mines. 

 When the ore is diffeminated in particles through the rock, 

 fuch rocks are alfo worked for the ore when it exifts in fuf- 

 ficient quantity. In fome inftances, maffes of ore of great 

 magnitude are found imbedded in rocks, without any ap- 

 parent conneftion with veins, which maffes muft^ have been 

 formed at the fame time with the rock itfelf. 



Rocks and ftrata are fometimes penetrated by metallic 

 falts or oxyds, diffufed through the mafs in the fame manner 

 as we frequently obferve ftrjta of fand-ftone abounding with 

 the red oxyd of iron. Where the metals are valuable, fuch 

 impregnated rocks or ftrata are fometimes worked as ores. 

 At Alderley Edge, a hill near Macclesfield, in Chefliire, the 

 fand-ftone, which is in fome parts a kind of breccia, is im- 

 pregnated with the black oxyd of cobalt, with tlje car- 

 bonate and oxyd of copper, and with particles of fulphuret 



and 



