Conversation so far:
What was The Old Boers regarding Jan Smuts?
At the 1913 South African Party conference, the Old Boers (Hertzog, Steyn, De Wet), called for Botha and Jan Smuts to step down.
Why was Jan Smuts called this?
Jan Smuts served as a Boer General during the Boer War
What did Jan Smuts do during the Boer War?
Jan Smuts was given three key ministries: Interior, Mines, and Defence. Undeniably, Smuts was the second most powerful man in South Africa.
What was the dispute with Jan Smuts over?
Jan Smuts was given three key ministries: Interior, Mines, and Defence. Undeniably, Smuts was the second most powerful man in South Africa. Smuts was criticized for his overarching powers.

Question: What were they mining?
Self-contained rewrite: What were they mining for?