THE TIN LODES OF CORNWALL. 421 



schist and sometimes capel ; hence the Great Flat Lode, being a 

 band of altered rock, is different from a vein as commonly understood, 

 and might be termed a tabular stock work. This deposit yields 

 more than one-eighth of the tin ore of Cornwall. 1 



Tin near Helston. Close to the turnpike road leading from 

 Penryn to Helston, and about four miles from the latter town, are the 

 tin deposits of the East Wheal Lovell. These lodes are usually very 

 narrow, sometimes only a couple of inches thick ; but in places rich 

 deposits of tin occur on both sides of the vein. There is a leader or 

 little vein of quartz, less than half an inch thick, running through the 

 granite, and on each side of it a quantity of tin stuff which is a 

 mixture of quartz, mica, cassiterite, pyrites, and other minerals. 

 There is no wall separating the tinny mass from the granite. Some- 

 times the tin was more developed on one side of the leader than on 

 the other. The main mass of the East Wheal Lovell extends like a 

 pipe from the forty fathom level to the no fathom level. Dr. 

 Eoster remarks that there are other pipes and bunches of tin ore, 

 similar to those which occur in the St. Ives district ; but they differ 

 in the absence of the mineral tourmaline. Concerning their origin 

 he observes that the leader was evidently an open fissure, so that 

 after the solidification of the granite, cracks were formed in it through 

 which vapours or solutions ascended, decomposed the felspar, and 

 deposited tin stone and other minerals among the constituents of the 

 granite. 2 



Tin Lode of St. Columb. Another important localit} 7 for tin is 

 Park of Mines, three miles south of St. Columb. The nearest 

 granite is a portion of the great mass north of St. Austell, which 

 approaches within three quarters of a mile. Many little veins run 

 from north to south through the clay slate, varying in thickness up 

 to a quarter of an inch. They occasionally enlarge to one or two 

 inches and contain cassiterite. Near these insignificant little strings, 

 lenticular masses of tin stone occur in the planes of bedding of the 

 clay slate. They are termed the east-and-west lodes, but correspond 

 to the deposits which when horizontal are termed floors in Cornwall, 

 and flats in the north of England. The only minerals associated with 

 the cassiterite are schorl, quartz, and kaolin. The clay slate near 

 the boundary of the tin layers is usually stained red by oxide of 

 iron. 3 



Tin of St. Agnes. In the St. Agnes district, Dr. Le Xeve 

 Eoster has described several tin lodes. One of these, known as the 

 Pink lode in the Penhalls Mine, east of Trevaunance Cove, extends 

 thirty-five degrees north of west in the clay slate. The leader 

 consists of quartz, cassiterite, chlorite, iron pyrites, and pieces of 

 capel, and has a width of from four to fifteen inches. The rock on 

 each side is termed capel, when by the infiltration of mineral solu- 

 tions it is changed from a soft slaty rock to a compact mass of quartz 



1 Dr. Le Neve Foster, Q. J. G. S., vol. xxxiv. p. 640. 



2 Trans. Roy. Geol. Soc. Cornwall, vol. ix. part II., 1876. 



3 Foster, Miners' Association of Cornwall and Devon Report, 1875. 



