MORE than 40 artisanal gold miners were killed in southwest Mali last week after the shaft they were working in collapsed, Mali's mines ministry said. Artisanal mining is a common activity across much of West Africa and has risen in recent years due to growing demand for metals and rising prices. Deadly accidents are frequent as artisanal miners often use old-fashioned and unregulated methods of digging. The incident in Mali occurred on Friday on a site in the Kangaba Cercle in the south-western Koulikoro Region, the mines ministry said in a statement on Tuesday that did not specify the number…