Mitchell, R.H. “Accessory Rare Earth. Strontium, Barium and Zirconium Minerals in the Benfontein and Wesselton Calcite Kimberlites”. International Kimberlite Conference: Extended Abstracts 5 (February 1, 1991): 292–294. Accessed November 22, 2024. https://ikcabstracts.com/index.php/ikc/article/view/2544.