656 



C. LE NEVE EOSTEIt ON SOME 



The stuff is trammed away a distance of about a quarter of a mile 

 to some stamps worked by water power ; and even at present prices 

 the poor tin-bearing rock, containing not more than 7 lbs. to the 

 ton of stuff, say one third per cent, black tin, may be made to pay 

 all expenses. 



Fig. 2. — Sectional view of Mulberry Mine. 



«^3 L 



^^^^^^^^ 



As in the case of Wheal Prosper, such a result could not be ob- 

 tained were it not for the fact that the rock is soft and the tin in 

 comparatively large grains. 



Minear Downs*. — About 1| mile N.E. of St. Austell is a deposit 

 very much resembling that of Mulberry Mine, which I have just 

 described. The great open quarry at Minear Downs is about 200 

 yards long at the top, and 60 or 70 yards wide, but only 90 

 yards long and 20 or 30 yards wide at the bottom. The greatest 

 depth can scarcely be less than 120 feet. These dimensions will give 

 an idea of the enormous amount of the tin-bearing rock which has 

 been removed. The tin-ore occurs in a series of more or less parallel 

 veins in the killas, striking about E. 7° S., and dipping N. at an angle 

 of about 70° ; the strings are often mere cracks, but occasionally 

 J in. wide, and lie from 2 inches to 12 inches apart. I counted ten 

 strings in one place in a width of 6 feet. They generally keep their 

 own course without much interlacing in dip and strike. The killas 

 itself dips S.S.E. at an angle of 20° to 25°, so that the strings inter- 

 sect it almost at right angles. At the sides of the strings the killas 

 is often stained red and yellow, and is occasionally altered into tour- 

 maline schist. 



On the S.W. side of the pit is a so-called lode, which is merely a 



* The word "Minear" is, of course, a corruption of Menhir, a Longstone. In 

 fact, the name of the farm is written " Menheir " on the Ordnance Map. I 

 use the spelling adopted by the present owners of the mine. 



