Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Amcol International (NYSE: ACO) shares plunged 10.1% in intraday trading today, after the minerals manufacturer reported lackluster quarterly results.

So what: You can't really blame investors for feeling jarred. This is the first time Amcol has missed analysts' estimates in six quarters. Worse yet, it missed profit estimates by a whopping $0.17 per share, even though it reported better-than-expected revenue. Higher costs have plagued the company, pinching its profit margins.

Now what: Amcol shares had been rising since last October, so today's pullback might seem like a good opportunity to buy in. However, the company's P/E of 18 sounds a little exotic for a minerals manufacturer. Before buying in, investors should wait and see whether today's developments are a one-time deal or a sign of things to come.

Interested in more info on Amcol International? Add it to your watchlist.