Note on the Occurrence of Remains of Recent Plants in Brown Iron-ore

Abstract

This bed of fossiliferous iron-ore is situated at Rio Tinto, in the province of Huelva, Spain, and is in close proximity to the celebrated copper-mines of that name. In this portion of Southern Spain deposits of cupreous iron pyrites, consisting of a series of lenticular masses of ore, having a general direction a little north of east and south of west, extend from Aznalcollar, near Seville, in the east, for a distance of more than seventy miles westward to within the Portuguese frontier. At Rio Tinto the deposits of this mineral are very extensive, and consist of a compact and intimate admixture of iron pyrites with a little copper pyrites, through which strings of the latter mineral sometimes ramify. Although these mines appear to have been worked, and the copper smelted upon the spot, from time immemorial, it is evident from the vast heaps of furnace-slags, and from the extent of the various other remains in which coins and inscriptions of the reigns of the Emperors from Nerva to ttonorius have been discovered, that their great development under the Romans took place during the first four centuries of the Christian era. After the f.~ll of the Roman empire they seem to have been abandoned down to as late as the year 1727, from which date they were intermittently worked by the Spanish Government and by ,~arious private speculators until 1873, when they were purchased by an :English company. The extent of the mining and metallurgical operations anciently carried on in