I was using up the last of my 2 week old beans that I picked up from a local roaster with a very good reputation. The espresso shots I have been able to pull from this batch have been great. I was able to find what I felt was close to the sweet spot on my grinder (Ascaso i3-mini) this morning. As I was grinding into my filter basket I started to hear this very subtle tink. I pulsed the grinder one or two more times and all of a sudden nothing. I thought oh great I just bought this grinder and I already bound up the burrs and killed it. I took the lid off of the grinder to investigate. At first sight I thought I saw what looked to be a very green bean stuck in the top of the burr. It had a greenish white black look to it and was the size of a bean. I was able to free it from the grinder burr and under further survey it turns out that it was a bean size ROCK. What the??

Has anyone found rocks in there beans before?

Thankfully the rock did not go very far down into the burr set, and I ground a fresh double shot right after the incident just to check on the grind quality. The shot I pulled was excellent, the best I have pulled yet, which in reality is not that many since I am a newbie. But enough to find a sweet tasting shot.

This happens more then one would imagine. A quick scan of the beans is in order before grinding.

I haven't found one in a while, and have always caught them before grinding, but I was thinking about this today while culling beans prior and pulling Quakers after a roast. It's probably more common with patio dried coffees and I'm always more diligent with Sweet Maria's Moka Kadir and Indonesian coffees.

Also, with the smaller, local roasters may not have the capitol to invest in de-stoners and coffee processing equipment to get the other debris (nails, etc.) out of the coffee and probably rely more on visual methods.

Read the Lizard Latte section of the following newspaper article for a list of other interesting things found in coffee here (www.signonsandiego.com, San Diego Union Tribune) which also features an article on Joe Behm, inventor of the Behmor 1600 coffee roaster I use to roast my coffee.

yakster wrote:Also, with the smaller, local roasters may not have the capitol to invest in de-stoners and coffee processing equipment to get the other debris (nails, etc.) out of the coffee and probably rely more on visual methods.

That's the key problem. The roasters I deal with have de-stoning equipment that hasn't failed me yet. If you home roast, you're even more on your own.

I've never had a rock in a bag from any of the roasters I've tried. I found a tiny rock in a bag of green from SM once, but even that was pretty unusual.

I roasted commercially (part time gig) for a local multi unit cafe operations. In the 2 1/2 years that I ran their Sivetz 1/4 bagger, roasting about 600 - 800 pounds per week, I found perhaps a dozen or so small rocks (ranged from smaller than a kernel of corn up to 3X that size.) Also found several dozen kernels of corn, all of which had popped or partially popped during roasting. Even found a full half coconut shell in one bag of Sumatran but obviously that never made it into the roaster.

It can happen, it's less common in the much higher end coffees, and small independent roasters are less likely to have de-stoning equipment in their production environment.

Found a pebble sized rock in my beans once but caught it before it went into the grinder, thank g-d...

I find them occasionally, a couple of times a year or maybe one per 100lbs of espresso. I almost always find them the hard way too . The ones I've hit tend to grind up with just a bit of extra noise and show up as white grains in the doser, though I've gotten the other kind too.

Even if your roaster has a de-stoner, they have to use it on every batch they roast for it to work. New guy in the roasting plant? Roaster hung over? Everybody's in a hurry on a Monday? Steps like that can be missed. Even then, I don't believe its a 100% effective system.

I emailed the guy the other day about finding the rock. His reply is as follows. Pretty interesting!

"I have found rocks in the raw beans several times - I even hand sift the beans before roasting to try a catch any that get past the "de-stoner" machines the coffee plants use to try to prevent this from happening. I have even found a few small nails, jewelry pieces, corn, wood, glass & wire in the raw beans. My broker once found a bullet casing in some coffee from Kenya! The reason this happens is that most of the coffee grown is sun dried on cement patios and every 15 minutes they turn the beans over with brooms to make sure the beans dry out evenly. The stones are picked up from the patios, workers boots ect. Every effort is made to clean out and debris in this process, but occasionally, stones get past - I'm just glad to hear your grinder was not broken. To date, I have not broken any burrs in my machines."

The best FOD story I heard was about 15 years ago... someone told me they'd had a .30-06 round cook off in the roaster.

It's amazing what the beans will hide, and how hard it is to see that stuff.

If as rock gets through to ceramic burrs it is predictably disastrous (I saw it happen with a small screw that got into beans post roast and went into the burrs of a Swift grinder - I think rocks woudl be just as bad.)