The chemical and mineralogical changes in silica brick used in a zebra roof was given in the previous paper, V. The present paper contains the results of a study on the changes observed in an unburned chrome-magnesia brick and its cladsteel plate coming into contact with a silica brick. The specimen was divided into seven zones according to their colors, chrome-bearing spinel grain and silicate matrix were separated using the heavy liquid method. The mineralogical constitution of spinel solid solutions and silicate matrix of each zone were calculated from the results of chemical analysis.The results obtained may be summarized as follows: On the chrome-bearing spinel grain; (a) A large excess of sesqui-oxides of iron and chromium were found in the spinel in the zones exposed to highest temperatures. (b) Excess (8-13%) of magnesia was present in the spinel contained in the lower temperature zones. (c) The amount of MgO⋅Al2O3 decreased in a marked degree, from 25% to about 8%, according to the increase of temperature to which the zones were exposed. (d) In the spinel embedded in the silicious glass matrix formed by the diffusion from silica brick, MgO⋅Al2O3 was absent, and texture of spinel grains in this area was turned into a porous substance composed from separated small pieces, which suggests that the selective dissolution of MgO⋅Al2O3.On the matrix; (a) In the surface layer of the chrome-magnesia brick coming in contact with silica brick and exposed to the highest temperature silicious glass penetrated into the brick up to about 10mm from the surface, and the dendrites of magnetite and cristobalite were present in the glass phase. Considering from the phase-equilibrium data it is highly probable that the formation of fayalite (m.p. 1250°C) from magnetite (m.p. 1590°C) by changing from oxidizing to reducing atmosphere gave more unfavourable influence on the refractoriness of the brick than the formation of monticellite (m.p. 1500°C) by the increase of lime content in the matrix. (b) The main constitutional mineral in the matrix in the middle zone was monticellite. (c) The conversion of chlorite to olivine in the original brick took place at the temperatures ranging from about 1100 to 1300°C.