Difference in spectral reflectivity between grains of homogeneous and exsolved titanomagnetite

SUMMARY. The spectral reflectivities of homogeneous and exsolved titanomagnetites of the same chemical composition were measured in air and in oil. The reflectivities of the two kinds of titano-magnetite are closely similar in the blue part of the spectrum, but become increasingly different when proceeding towards the red end. The refractive indices (n) and the absorption coefficients (k) were calculated from the reflectivity values. The n-values of the two kinds of titanomagnetite show a pattern of separation similar to that of the reflectivity values. Regarding possible differences between the k-values no reliable conclusions could be drawn. Some possible xplanations ofthe observed separa-tions are discussed. THE present paper forms the first part of an investigation of the relations between chemical composition and spectral reflectivity in the magnetite-ulv6spinel s ries. Reflectivity measurements have earlier been made on a homogeneous titanomagnetite (Cervelle, 1967), magnetites from different localities (Demirsoy, 1968), lunar ulv6spinel (Cameron, 197o), and on homogeneous titanomagnetites of varying compositions (Pr6vot and Mergoil, 1973). From these measurements reflectivity values for some compositions in the magnetite-ulv/3spinel s ries have been obtained. However, t