ORIGIN AND DEVELOPMENT OF ORE-DEPOSITS. 129 



were always far more complex. in character. " The dip is S.W., 

 varying from 75° at the S E. part, to 60° at the N.W. extremity 

 of the workings. The structure of this lode deserves particular 

 attention ; the so-called lode consists of four or five small parallel 

 tin veins, bounded on each side by a hard rock locally known as 

 hardworh, which merges into granite. The total width of the 

 lode varied from 10 to 20 feet, and averaged about 12 feet. 

 Each little vein or leader, known at Balleswidden as a gry, was 

 generally about a half-inch thick and rarely widened out to more 

 than 4 inches. The gries rarely united with one another along 

 the dip or the strike, but often dwindled away to a mere string 

 or joint. The filling up of these little veins consisted of coarsely 

 crystallized tin stone, with schorl, quartz, gilbertite and kaolin 

 [prian) ; a little wolfram, fluor-spar, bismuthine, and native copper 

 were also sometimes met with. The little veins or gries were 

 continuaRy varying in productiveness ; as a rule only one of them 

 was rich in any given section, and as soon as it began to dwindle 

 away one of the neighbouring ones began to improve. There 

 was always a sharp and well-defined wall between fkegry and the 

 adjoining hard-work, and this was of importance to the miner as 

 it enabled him to separate the rich gry from the poorer rock 

 adjoining it, and make a little parcel of best work." The greater 

 part of the tin was contained in the "gries," but the hard- work 

 also contained a little tin. Associated with the so-called lodes 

 were certain off-shoots or " pie-lodes," which much resembled 

 the carbonas of the St. Ives district, yet to be referred to, but 

 differed from them in containing less schorl and more gilbertite 

 when really productive. The mine was worked to a depth of 

 about 150 fathoms. During the 36 years that the adventure 

 lasted, from February, 1837 to April, 1873, more than 12,000 

 tons of black tin were sold, of a value of £694,094, besides 

 certain small quantities raised and sold before and since.* 



Beam. This mine is about four miles north of St. Austell, 

 on the north side of the Hensbarrow granite. It is many years 

 since it was worked, and the latest published description is that 

 given with plan and sections in my "Hensbarrow granite district," 

 in 1878. It is said to have been first worked as an open cutting in 



* Ibid, p. 17, 



