Behaviour of the critical elements As, Bi, In, Sb, and Te during processing of a skarn ore: A case study of the Ruwai Zn-Pb-Ag Deposit, Central Kalimantan, Indonesia

Abstract

Advancements in modern technology are causing a rapid increase in the consumption of critical elements. Many of these elements are obtained as by-products from the extraction and processing of other raw materials. Yet, limited information is available on their concentrations in primary ores, behaviour during ore processing, and availability to the global economy. This study analysed ores and mineral processing samples from the Ruwai Zn-Pb-Ag skarn deposit to constrain the process behaviours of the critical elements As, Bi, In, Sb, and Te, alongside Ag and Cd, through mass-balancing.

Bismuth and Te primarily report to the Pb concentrates at rates of 79–91 %, and 59–77 %, respectively, with losses to tailings below ∼20 % for Bi, and ∼30 % for Te. Antimony recovery to the Pb concentrate is lower (34–52 %), with notable losses to tailings (45–62 %). Indium preferentially reports to the Zn concentrates at rates of 61–84 %, with 14–33 % lost to tailings. By contrast, As is mostly lost to the tailings (77–86 %), with low recoveries in both the Pb and Zn concentrates (5–15 %). Silver and Cd show high recoveries (>76 %) to either the Pb or Zn concentrates. The similar behaviours of Ag, Bi, Sb, and Te to Pb, and Cd and In to Zn, suggest that these elements are either hosted by galena or sphalerite, or by minerals that behave like galena and sphalerite during the flotation process.

The results of this study have major implications for the estimation of critical-element mass flows worldwide, providing the first detailed mass-balance data for As, Bi, In, Sb, and Te from a Zn-Pb-Ag skarn deposit.