John Slack at Spanish River Carbonatite Complex Educated at the Haileybury School of Mines, John Slack is a Canadian mining technologist-turned-farmer who uses his thorough understanding of geology to promote remineralization and sustainable soil fertility. “Promoting the use of rock dust — and the throwing away of your fertilizer bag — has been a really tough row to hoe, but we’re now going to see major breakthroughs, particularly as we move to a ‘greener’ environment, where people are thinking about this more,” he said. “The fact of the matter is it does work.” Slack began his professional life employed with a progressive ...