The paper aims at determination of parameters, approximate to optimal, of pneumatic separation of the mixture of wild cornflower dried petals obtained by mechanical harvesting. Moreover, the investigated raw material contamination was assessed through comparison and identification of various groups of contaminants and undesired components of the mixture in the basic raw material. Separation was carried out in a horizontal air stream with the use of the designed pneumatic separator. The most efficient and effective was the process of petals separation at the air stream velocity which was 4 m∙s-1. The amount of the obtained clean petals from the mixture in case of a fraction with bigger dimensions was 48.3%. With the increase of the air stream velocity the coefficient η increases but along with this, the amount of a valuable fraction, which is taken by the stream, grows. At the growth of air stream velocity from Vs=4 m∙s-1 to Vs=6 m∙s-1 (within the same size fractions), the highest increase of the coefficient η was in case of the fraction of 400÷500 μm and was 48.3%.