Diamond placers in the region of Franca, State of São Paulo, Brasil

Abstract

This paper presents an organized set of information concerning the diamantiferous region of Franca (State of São Paulo). The interpretation of aerial photographs, observations from helicopter surveys and field work allowed recognition of 428 indicators of diamond presence; 55 of those have been confirmed. Most of them are scateered along the terraces and alluvial plains of the Sapucaizinho, Santa Barbara and Canoas rivers. An annual production of some 1,000 ct is estimated, mostly (70-80%) small gems smaller than 35 points. Grades are presumed to vary from 0.02 to 0.18 ct/m³, comparable to currently available values for this kind of placer. Many legal, environmental and human problems related to diamond prospection and exploitation in the area remain to be solved