Chalcopyrite (CuFeS₂) was identified as the main constituent of Trent sand, a naturally-occurring abrasive that until the last few years was traditionally employed in the Birmingham (England) Jewellery Quarter for buffing metal. Since chalcopyrite is one of the chief ores of copper and has not heretofore been identified in an abrasive, the possibility exists that excavated particulate chalcopyrite used as a polishing material may be misinterpreted as dressed ore. The same possibility of misinterpretation holds true of blacksmiths' iron scale.