The mullihercynitite is a new type of volcanic rock discovered for the firsttime, composed of hercynite,mullite, pseudobrookite and volcanic glass. Its chemi-cal composition (%) is given as follows: SiO_2 35. 32, TiO_2 3.99, Al_2O_3 32.25, Fe_2O_319. 90, FeO 6. 20, MnO 0.17, MgO 0.39, CaO 0.05, Na_2O 0.74, K_2O 0.09, P_2O_5 0.16,H_2O~+ 0.98 and H_2O~-0.03, correspondine to. that of a simplified SiO_2-FeO-Al_2O_3ternary system. Mulliher-cynitite magma results from deep-seated differentiationof primary basaltic magma, from which orthopyroxene rich in jadeite and clino-pyroxene are removed in the deep levels of the mantle. The magma evolves towardthat rich in Al and Fe and poor in Si and finally mullihercynitite magma isproduced. The mullihercynitite magma is erupted on the surface and crystallizesto produce mullihercynitite.