You have to consider where some of these materials stocks have come from. After recent gains you can expect some natural sellers in the market.
They have been investing for some time. But obviously low amounts.
The metals boom continues and it's very hard to see where it will stop. Investors are so focused on the Chinese raw materials boom that share prices have become an afterthought.
The drops came during the reporting season when some investors, including myself, were concerned about the rally in resources shares. Strong gains in metals prices have reassured the market.