The processing of granitoids as part of the production of stone elements or crushed aggregates generates significant amounts of fine-grained rock wastes in the form of solids or slurries. Problems with their rational management cause processing plants to most typically store them in waste dumps. Only a small part of these wastes is used in the construction or ceramic industries. Their effective use, in line with the ideas of circular economy, has a significant influence on the natural environment, as well as on the efficiency and profitability of processing plants. This type of waste is typically treated as fine-grained waste rock material, with no attempts being made at separating its mineral components. This article presents an analysis of the properties of rock wastes from the production of granite slabs. The tests were performed on samples of fine-grained wastes from the cutting of granite dimension stones mined in the Strzegom massif (Poland). The tests included a physical and chemical analysis and a grain size analysis, as well as magnetic separation of iron-bearing minerals. The results indicate that such wastes are fine-grained, with a chemical composition similar to that of primary materials, but also with an elevated iron content. The analysis of the results of magnetic separation indicates that it is possible to reduce the content of iron in the investigated samples. The results are a basis for further research into a mineral separation technology in the processing of rock wastes from the production of granite slabs and into concepts of their economic usage.