Note 215 — Chapter IV · THE PROTO-CHALCITIC OR COPPER AGE OF WEAPONS.
Reading edition
They abandoned the native silver mines when the ore became too hard, and they smelted it in small portable stoves. They knew also the chemical combinations, sulphate, antimonial, and others; and they worked quicksilver. They had mines of Quella (Khellay, or iron), but they found difficulty in extracting it. Besides smelting, they could use the tacana (hammer), cast in moulds, inlay, and solder.