euphotides

The abundance of copper mentioned by the Conquistadores of the sixteenth century, at a period when the Spaniards were more attentive than they have been in latter times to the natural productions of America, may possibly be attributed to the formations of amphibolic slate, transition clay-slate mixed with diorite, and to euphotides analogous to those I found in the mountains of

Travels to the Equinoctial Regions of America 1851

The abundance of copper mentioned by the Conquistadores of the sixteenth century, at a period when the Spaniards were more attentive than they have been in latter times to the natural productions of America, may possibly be attributed to the formations of amphibolic slate, transition clay-slate mixed with diorite, and to euphotides analogous to those I found in the mountains of Guanabacoa.

Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 3 Alexander von Humboldt 1814