Stones in Coffee

This evening, while roasting up a batch of Mexican coffee from the Comalapa region for the coffee drinkers at my office, I noticed something strange spinning in drum with the beans. After looking closer it was obviously a stone of some type. Stones are really not fun to get in coffee, primarily because they can wreck a coffee grinder by jamming in the burrs. Since many coffee grinders are rather expensive, this can be a fairly serious problem.

Unfortunately, stones seem to be somewhat common issue for coffee roasters, and larger operations actually use machines called destoners to remove stones from roasted coffee.

Once I dropped the roast and got the beans cooled down, I sifted around and found the stone pretty quickly. Turns out it was a small piece of concrete. I haven’t ever run into this with beans I’ve gotten from La Bodega before, so I’ll keep an eye on it. I’d sure hate to ruin my (or anyone else’s) grinder.