Tin slag results from smelting of tin ores such as cassiterite. Tin slags are widely used as an aggregate for Nb-Ta production due to their high contents in those refractory metals (Odo et al. 2014). Most of the tin worldwide is produced in China and Southeast Asia but there is also production in many other countries in South America, Africa and Europe (Elsner 2014).
Elsner, H., 2014: DERA Rohstoffinformationen: Zinn-Angebot und Nachfrage bis 2020 (Tin - Supply and demand until 2020, in German). DERA, Deutsche Rohstoffagentur in der BGR.
Odo, J. U., W. C. Okafor, S. O. Ekpe, and C. C. Nwogbu. (2014) Extraction of Niobium from Tin Slag. International Journal of Scientific and Research Publications, 4.