Feature Gems & Gemology, Spring 1985, Vol. 21, No. 1

Sapphire from the Mercaderes-Río Mayo Area, Cauca, Colombia

Commercially important quantities of gem-quality sapphire are being recovered from stream beds and terrace gravels near the Colombian village of Mercaderes, about 143 km southwest of Popayán. The area is currently subject to a high degree of political unrest; nevertheless, about 100 people are said to be sporadically mining the deposit. Sapphire crystals average about one centimeter in length and occur in a variety of colors. Color-change stones are also common. Three inclusions were found to be characteristic: apatite, rutile, and boehmite. The parent rock for the sapphires has not been established, but it is probably one or more of the alkalic basalt members of the Cretaceous-age Diabase Group which outcrops in the area.