Grains of natural moissanite were extracted from heavy fraction of Yakutian kimberlites and from Triassic sediments in Bulgaria. Results of the investigation of samples' morphology, trace element composition and of polytype abundancy are reported. Main impuritites are: Al, Co, Ni, Fe. Usually the samples are chemically uniform, though in several cases heterogeneous distribution of Al was observed. Some of the grains contain pressurised inclusions of native Si, identified by microprobe and Raman spectroscopy. Preliminary LAM-ICP-MS results on trace elements show unexpectedly high abundances of incompartible elements, especially along the contact inclusion-matrix. It is suggested that the formation of natural SiC is related to metasomatic processes. The grains are represented by 6H and 15R polytypes as well as their mixture (disordered SiC).