Steel production from basic oxygen steelmaking accounts for approximately 1.35 billion tons of steel per year. Each ton of steel produced generates between 100 and 200 kg of slag. Extrapolated, this means that between 135 and 270 million tons of slag are produced each year. While a significant portion of this slag is used in the construction sector, a considerable amount is also landfilled. This landfilling not only results in the loss of large areas of land but also creates the problem of losing valuable metals. Iron, chromium, and other important components contained in slag are lost for further use and represent a waste of resources that should not be underestimated. Therefore, it is crucial to develop sustainable strategies for optimal utilization of BOF slag to reduce soil degradation and loss of valuable metals. This scientific study focuses on deepening and extending the value chain of steelmaking slags. Special attention is given to the potential of the valuable metals contained therein to gain a deeper understanding of their importance and potential uses. As an introduction, the main principles of BOF steelmaking are presented in a detailed theoretical section. Further to the environmental aspects, the various physical, chemical, mineralogical, and morphological properties of the slag are explained in detail. In addition to the theory, various recycling approaches are discussed, considering both academic perspectives and industrial approaches. The practical part of this study focuses on the investigation of BOF slag formation and crystal growth. First, four different slag samples were characterized. The characterization results show that as the C/S ratio increases, not only does the melting interval of the slags become wider and occur at lower temperatures, but the morphology tends toward more pointed grains. Also, an examination of the slag at a temperature of 1100 °C was performed by scanning electron microscopy. It was found that oscillating heat treatments can separate calcium silicates and iron fractions. Towards the end of the work, various experiments were carried out with the slag and different additives at different temperature programs. It is noteworthy that when Al2O3 was added and the holding temperature was 1350 °C, the formation of spinels was observed, but they disintegrated after some time. Furthermore, spinels were grown by the addition of Al2O3 alone and in combination with B2O3 at a temperature of 1410 °C. Analyses showed that these spinels had a chromium content of up to 7 %.