The discovery of nearly 3,000 diamonds in dolerite and other mafic rocks in Anhui's Lan'gan area, is the first such occurrence in China. Although the host rocks' characteristics and petrogenesis are well-constrained, diamond genesis remains unclear. This study conducted petrographic and compositional analyses of the characteristic accessory minerals, namely garnet and ilmenite, within the dolerite. The results show that the garnet appears pale red, elliptical to sub-angular in shape, with large grain sizes (450 ~ 600 μm), and exhibits low MgO (0.54% ~ 13.65%) and Cr?O? (0% ~ 0.26%) contents. The ilmenite is black, sub-angular in shape, with large grain sizes (500 ~ 600 μm), and has low MgO (0.42% ~ 2.35%) and Cr?O? (0% ~ 0.05%) contents. Both garnet and ilmenite are xenocrysts, and their mineralogical characteristics are significantly distinct from indicator minerals in typical diamond-bearing kimberlites (e.g., the Wafangdian 30th pipe in Liaoning, China, and the Big Hole pipe in South Africa). This indicates that the characteristic accessory minerals in the Lan'gan dolerite are not derived from kimberlites, and the diamonds contained therein show no genetic link to kimberlites. The composition of garnet further reveals that its material source is pyroxenite and eclogite, implying that the dolerite magma once incorporated breccias of these rock types. Consequently, the diamonds in the dolerite e may be inherited from partially assimilated diamonds within the breccia clasts.