BOOK V. 117 



which the tin itself is made, and a material they dig up resembhng litharge ; 

 of iron, iron rust. Gold and copper are equally indicated by chrysocolla and 

 azure ; silver and lead, by the lead. But, though miners rightly 

 call bismuth " the roof of silver," and though copper pyrites is the common 

 parent of vitriol and melantena, still these sometimes have their own 

 pecuhar minerals, just as have orpiment and stibium. 



Now, just as certain vein materials give miners a favourable indication, 

 so also do the rocks through which the canales of the veins wind their 

 way, for sand discovered in a mine is reckoned among the good indications, 

 especially if it is very fine. In the same way schist, when it is of a 

 bluish or blackish colour, and also limestone, of whatever colour it may be, is 

 a good sign for a silver vein. There is a rock of another kind that is a good sign ; 

 in it are scattered tiny black stones from which tin is smelted ; especially when 

 the whole space between the veins is composed of this kind of rock. 

 Very often indeed, this good kind of rock in conjunction with valuable 

 stringers contains within its folds the canales of mineral bearing veins : if 

 it descends vertically into the earth, the benefit belongs to that mine in 

 which it is seen first of all ; if inclined, it benefits the other neighbouring 

 mines^2. As a result the miner who is not ignorant of geometry can calculate 

 from the other mines the depth at which the canales of a vein bearing rich 

 metal will wind its way through the rock into his mine. So much for these 

 matters. 



I now come to the mode of working, which is varied and complex, for in 

 some places they dig crumbhng ore, in others hard ore, in others a harder 

 ore, and in others the hardest kind of ore. In the same way, in some places 

 the hangingwaU rock is soft and fragile, in others hard, in others harder, and 

 in stiU others of the hardest sort. I call that ore " crumbling " which is com- 

 posed of earth, and of soft sohdified juices ; that ore " hard " which is composed 

 of metaUic minerals and moderately hard stones, such as for the most part 

 are those which easily melt in a fire of the first and second orders, hke lead 

 and similar materials. I call that ore " harder " when with those I have already 

 mentioned are combined various sorts of quartz, or stones which easily melt 

 in fire of the third degree, or pyrites, or cadmia, or very hard marble. I call 

 that ore hardest, which is composed throughout the whole vein of these hard 

 stones and compounds. The hanging or footwalls of a vein are hard, when 

 composed of rock in which there are few stringers or seams ; harder, in 

 which they are fewer ; hardest, in which they are fewest or none at all. 

 When these are absent, the rock is quite devoid of water which softens 

 it. But the hardest rock of the hanging or footwall, however, is seldom as 

 hard as the harder class of ore. * 



Miners dig out crumbhng ore with the pick alone. When the metal 

 has not yet shown itself, they do not discriminate between the hangingwaU 

 and the veins ; when it has once been found, they work with the utmost care. 

 For first of all they tear away the hangingwaU rock separately from the vein, 

 afterward with a pick they dislodge the crumbhng vein from the footwaU 



**Presumably the ore-body dips into a neighbouring property. 



