1 The minerals produced are tin, gold, iron, galena and others, in insignificant quantities.
Cambrian, Ordovician and Silurian beds have been recognized, the Upper Cambrian consisting of a limestone which is very rich in metalliferous ores (especially galena and calamine).
The lodes are most frequently of great size, containing huge masses of galena, and so little gangue that the ore can very easily be dressed to 83 or 84%.
The government let the mines to contractors for forty years and then took them over; but in the period from 1720 to 1840 only 14,620 tons of galena were extracted and 2772 of lead.
The most important minerals are lead and zinc, obtained in lodes in the forms of galena and calamine respectively.