45(5 Geological Society. 



surface. The usual width of the veins that are worked 

 varies from one foot to three ; in particular instances, how- 

 ever, portions of veins occur 24 feet or even 30 feet wide, 

 and on the other hand a vein of tin ore not three inches 

 wide has been followed with profit. 



The substances that accompany the metallic ores (or the 

 veinstone?) vary considerably, not only in different veinsi 

 but in different parts of the same vein ; and it is from these, 

 and not from their metallic contents, that the miner's no- 

 menclature of the veins is derived. 



Gossan is a friable substance of a loose texture, consist- 

 ing of clay, mixed more or less with siliceous matter, and 

 coated or tinged with oxide (jf iron ; its colour varies from 

 light yellow to deep red and brownish black. A gossany 

 lode is more comiiiun than any other, and is considered as 

 prop. ising both for c(^pperand tin. 



When quartz predominates, the vein is said to be sparrv ; 

 and \\ the quartz is considerablv compact, it is looked upon 

 as a very unfavourable indication, more especially if the vein 

 becomes narrower as it desc?nds. 



If iron pyrites abounds, the vein is said to be mundicky. 

 When this substance occurs at a shallower level, it is con- 

 sidered as not unpromising, more especially if mingled with 

 yellow copper ore as it descends. 



A vein containing a large proportion of chlorite is termed 

 a peachy lode, and promises for tin rather than for copper. 



A veni is said to be fioohimj, when one or both of its 



.sides is lined with hlueish vvhiteclay. It sometimes is so 



abundant as to occasion considerable difficulty and expense 



to prevent it from slipping down and obsfucling the 



works. 



When the contents of a vein consist of a hard substance 

 of a greenish or brownish colour, which appears to be 

 chiefly a mixture of quartz and chlorite, the vein is deno- 

 minated caply. Tin is often found in it, copper rarely. 



When the ore, whether of tin or copper, is found m de- 

 tached stones orlumps, n'tixed loosely with the other con- 

 tents of the veins, itjs termed d prymiy lode. 



A vein abounding in blende is called a black jack lode, and 

 is considered as unpnmiising for tin, but a good sign of 

 copper. 



When a vein contains granite in masses or blocks, or in 

 a state of semi decoiriposiiion, it is termed a growan lode, 

 and is generally considered as more promisiiig for tin than 

 for copper. Of late, however, many rich veins of copper 

 have been found in the granitcdistrict of Cornwall. 



The 



