This project investigates the effect of trace-metal (Ag, Pb, Zn, Mn, Fe, and Ce)
concentrations on the photoluminescence (PL) and cathodoluminescence (CL) properties
of hydrothermal calcite veins from the historical Batopilas native silver mining
district. The calcite veins studied exhibit PL colors ranging from red-violet to pink to
orange in short wave ultraviolet light (254 nm). Red-violet exhibits the least intensePL
and orange the strongest PL. Calcite veins exhibiting pink PL host Pb, Zn and Ag sulfides
and native Ag.
Trace-element analyses show that concentration of Mn increases from 1,000 to
10,000 ppm and Ce from 10 to 100 ppm with PL color variation. The other trace-elements
show variable patterns. These data lead to the conclusion that Mn and Ce are
the main controls on PL color and intensity. CL emission spectra peaks in all samples
are approximately 600 nm, but intensity varies from 500 counts to 1,800 counts and is
perhaps related to Zn content.
This study does not identify a PL or CL method for differentiating veins consistently
or exclusively hosting silver. However, they do indicate that ore minerals, including
silver, preferentially occur in veins of pink PL; that Mn and Ce are sensitizers
affecting color and intensity of calcite CL; and that Zn concentration is proportional
to CL intensity increase.