MINERALOGY. 



439 



veins of calc-spar 140 feet wide, traversing gneiss, in 

 the valley of Lauterbrun, in the Alps of Switzerland, 

 la the island of Arran we obierved a vein of porphyry- 

 slate nearly 160 feet broad, traversing sandstone. Horn 

 mentions that the Spitaler vein at Schemnitz, in Hun- 

 gary, is from 14 to 15 fathoms wide. In that part of 

 the Fichtelgebirge that belongs to Bavaria, there is a 

 vein from 42 to 70 feet wide ; and in the country of 

 Holberg, near Rotleberode, there is a vein of fluor-spar 

 35 feet wide. In this country there are vein* of pitch- 

 stone and greenstone from 10 to 100 feet wide. 



The width of veins does not continue the same 

 throughout, but change* considerably, and in some par- 

 ticular veins in a remarkable degree. 



2. Length of Vein* Veins differ very much in their 

 length : when their length exceeds 6000 feet, it is to 

 be considered as uncommon. The following may be 

 mentioned as instances of metalliferous veins of un- 

 common length : The Halsbruckner-spath near Frey- 

 berg, which has been traced above four miles and a 

 half; the Mordlauer-flach vein in the Firhtelgebirge, 

 9000 fathomi ; and the Friedensgrubner-flach vein, in 

 the same mountain*, 5000 fathom*. Greenstone and 

 pitchstone vein* may be traced some miles in this coun- 

 try, as in the i-Uml of Arran. 



Deph of 3. Depth of f'eim Few metalliferous veins reach 

 'int. above 2OO fathoms below the surface of the moun- 

 tain* in which they arc situated, and still fewer continue 

 metalliferous to the depth nf 300 fathoms. The fol- 

 lowing are instances of veins which are metalliferous 

 at the depths mentioned : 



FaUMM. 



The Kuchschat vein near Freyberg, at --M7 



The irke vein near Freyberg, at 158 



The Thurnil.otVr vein, also near Freyberg, at 300 

 The Samson vein at Andreatberg, at . 250 



The Thurmhofer-shaft at Clausthal, at . S12 



The deepest shaft on a vein i that at Kuttenbcrg 



in Bohemia, .... 500 



Part* of * That part of a vein which appears at the surface 

 cin*. f mountain is denominated its outgoing at crop ; the 

 directly opposite boundary its bultom; and the lateral ex- 

 tremities, its end*. Those planes that bound the vein ac- 

 cording to its greatest extent, are termed its taalbaiulc 

 or tide*. 



Direction 5. Vein* continue in general in one direction. It 

 of rein*. must be understood that we here allude to the general 

 direction. A vein of a mile in extent may stretch north 

 and south in general, but there may be many devia- 

 tions from that during to long a course. 



Inclination 6. Veins are usually much inclined, always wore so 

 of t tin*. than beds ; the average inclination of beds is 45, that 

 of veins much higher. In inclined veins the upper 

 side is denominated the hanging tide, and the lower 

 side the lying ride. 



2. Structure and Internal Relations of Veins. 



1. The mass or body of a vein, as we have already 

 observed, is almost always different from that of the 

 rock which it traverse*. In tome cases, however, we dis- 

 cover resemblances between mountain-rocks and vein, 

 stones. Instances of this kind are porphyry and granite. 



- A principal character of veins is their division into 

 into branches. The vein is sometimes divided into many 

 * branches by fragments of the tralU (nebengestein ;) or 

 branches shoot out from the sides of the vein in differ- 

 ent directions, and either terminate gradually in the 

 rock at a greater or less distance from the vein, or, by 

 winding, again join it. 



It is observed that small veins usually terminate in Geognosy, 

 the manner of these lateral branches ; but large veins, < "~~r^ 

 on the contrary, divide into numerous branches at their 

 end-; and bottom, but less frequently at the bottom 

 than at the ends. 



3. The mass of the greater number of veins is sepa- Besteg of 

 rated from the rock through which it passes, by a very "in- 

 delicate seam ; but in others this is not the case. Some. 



times the sides of the vein are coated with a clayey 

 substance, which is denominated Bestfg by the German 

 miners ; but this does not always continue throughout 

 the whole extent of the vein in which it occurs. In 

 other cases the substance of the vein is intimately mix- 

 ed with its walls. 



4. Veins are composed either of earthy masses, as SubtUncci 

 clay or loam, or rocks, as granite, clay-slate, alum-slate, of which 

 porphyry, sandstone-conglomerate, sandstone, flcctz- '"> are 

 limestone, coal, basalt, wacke, greenstone, pitchstone, """P **^ 

 porphyry-slate, or ores of different kinds. There is 

 scarcely any species of ore that does not occur in veins. 



5. Some veins are composed of but comparatively Structure 

 few minerals, and these are massive and intimately ag- of vcioi. 



: L-d together ; others are composed of a greater 

 variety of minerals, but which shew little regularity in 

 their structure ; and lastly, veins frequently occur hav- 

 ing a regular structure, where the different materials 

 are arranged in layers parallel among themselves and 

 to the wall* of the vein ; and these throw great light 

 on the origin of veins, and on the formation of the mi- 

 nerals they contain. 



When veins are Composed of different layers, or are 

 stratified, the same succession of layers is to be observ- 

 ed from both sides towards the middle. Each suc- 

 ceeding layer rests on the preceding, in such a 

 manner that the crystals of the second layer are al- 

 ways impressed by those of the first. A beautiful 

 example of the venigenous bedded structure occurs 

 in the vein Hulfe-Gottes, at Gersdorf in Saxony. 

 This vein is from six to nine feet wide, and is composed 

 of parallel layers, which sometimes amount to forty in 

 number. These layers are composed alternately of calc- 

 spar, fluor-spar, lead-glance, grey copper-ore with 

 fluor-spar, heavy-spar, and a very small portion of 

 quartz. Similar appearances occur at Leadhills, and 

 in many other mining districts. 



In veins of this kind, in particular, we frequently 

 meet with openings or unfilled spaces, which are gene- 

 rally situated towards the middle of the vein, and are 

 by miners denominated Dnuet. They have usually a Druse*, 

 longish shape, and are always parallel with the vein. 

 They have various contractions and widening*. They 

 vary muah in size, being from a few inches to several 

 fathoms in magnitude. Their surface is covered with 

 crystals, which are usually of the same minerals as those 

 that form the massive part of the vein. Thus, the druses 

 in veins composed of quartz, are lined with quartz- 

 crystal* ; those in veins of brown-spar, with brown- 

 spar crystals. When druses are lined with a variety of 

 crystallizations of different minerals, we observe that 

 the one series is laid on the other in a determinate or- 

 der ; the oldest part of the formation being that on 

 which all the other crystals rest; the newest, that which 

 covers all the others. Druses are sometimes filled with Druses 

 water ; and when they are of great izc, the quantity of mott "" 

 water they contain is so considerable, as to endanger m 

 the lives of miners, when they are cut into. It is also * 11 



observed, that druses occur most abundantly, and of 

 greatest size, in the upper part of veins, but become 

 gradually smaller, and less numerous in thedeeper parti. 



