The mineral deposits of the San Antonio mine, in the Santa Eulalia district of Chihuahua, Mexico, occur in Upper Cretaceous and possibly Lower Cretaceous limestones. They lie within a downfaulted limestone block, are closely associated with a zone of acid dikes, and form replacement deposits of the contact-metamorphic type.
The chief yield has been lead and silver ore, but tin and vanadium ores have been produced commercially. The bodies are unusual in that lead and vanadium are important products from a contact-metamorphic area and in that tin occurs in replacement deposits in limestone.
Detailed descriptions of tin and vanadium ore bodies are given. The writer concludes that tin was the last ore element to be introduced and suggests it may have been pneumatolytic ; that the vanadium ore has been derived in large measure from the breakdown of primary vanadium-bearing silicates; and that the deposits are best classed in the pyrometasomatic group, of contact origin.