Why does my coffee have rocks in it?

Finding a rock in your bag of coffee is a jarring experience, but it is a well-documented issue in the industry known as 'foreign matter.' During the processing of green coffee, cherries are harvested, depulped, and dried. Ideally, the final stage before export involves rigorous cleaning, where machines like destoners and optical sorters remove debris that may have been collected during the harvest or drying process.

When a rock makes it into your bag, it is a sign that these quality control measures failed. In large-scale commercial operations, the sheer volume of coffee can sometimes overwhelm mechanical sorters. In smaller, less-mechanized farms, the reliance on manual labor or basic equipment increases the risk that small stones—which are often similar in size and density to coffee beans—will slip through the cracks.

From a consumer perspective, this is a significant quality issue. Beyond the unpleasant taste of a ruined brew, the primary danger is to your equipment. A single small stone can shatter the burrs of a high-end grinder, leading to costly repairs. This is why professional roasters often run their roasted coffee through a final destoner before packaging, though even this step is not infallible.

If you find rocks in your coffee, it is a valid consumer complaint. It suggests that the roaster’s quality assurance protocols are lacking. You should contact the roaster immediately, as they will likely want to know about the batch issue to prevent damage to other customers' equipment. In the world of specialty coffee, where traceability and quality are paramount, the presence of foreign matter is considered a major failure in the supply chain.