J813.] Mlneraloglcal Observations on Cornwall. 351 



veins is copper pyrites. The arseniates of copper, &c. are too 

 small in quantity to be of any importance in a mining point of 

 view. Iron pyrites and arsenical pyrites are likewise very 

 common attendants. They are both confounded under the name 

 of mundic. Wolfram is rather scarce ; for I did not observe 

 any specimens of it in any of the mines that I visited. Fluor 

 spar is a very common veinstone. It is always green, and is 

 distinguished by the name of green spar. Galena occasionally 

 occurs ; sometimes, as in Huel Anne, in such quantities that it 

 is collected and sold. In these cases its never-failing companion, 

 blende, is also met with ; and blende is likewise in some mines 

 collected and sold. In the united mines on the south side of 

 Huel Unity I observed a good many specimens of native copper 

 among the ore. The arseniate of lead, a beautiful mineral lately 

 analysed by Mr. Gregor, has only been found in Huel Unity 

 mine, in a cross vein at some considerable depth. It was in the 

 same mine, unless I am mistaken, that some of the finest speci- 

 mens of the arseniate of copper occurred. Green mica, or oxide 

 of uranium, has been found at Beeralston, at the eastern extre- 

 mity of the county ; and Mr. Gregor showed me a yellow variety 

 of the same ore from a mine in the parish of St. Steven's. It 

 was in the same mine that the sulphuretof tin formerly occurred. 



Besides the veins running easterly and westerly, which are 

 those of the most consequence, there are other veins which run 

 from north ro south, and on that account are called cross courses. 

 These veins are usually filled with quartz. They sometimes 

 contain ores, but most commonly not. They constitute the 

 newest of the L'crnish veins; for they always cut through the 

 other veins, and frequently alter their positions ; so that the 

 portion of the vein on the west side of the cross course lies far- 

 ther north than the portion of the same vein on the east side. 

 These cross veins vary in breadth from a few inches to 20 

 fathoms. The greatest of them is about three miles east from 

 Redruth, and has been traced from sea to sea. In some places 

 it is 20 fathoms wide, in others only a few feet. It heaves all 

 the veins which it crosses about 50 fathoms. That portion of 

 the vein on its west side is 50 fathoms farther north than the 

 part of the vein on the east side. 



The tin ore is always ti/h/o/ie, or oxide of tin. This ore 

 extends the whole length of the mining district. The Scilly 

 Islands contain the same vein-, and formerly tin mines were 

 wrought in them. No doubt this was the reason why they 

 received from the ancients the. name of Cassiteridcs, for 

 xao-o-iTf^,;, M every body kuo\ss, is the Greek name for tin. 

 During Queen Elizabeth's reign considerable quantities of tin 

 were rai.-cd in Dartmoor. Hence there can be no doubt that 



