The grain boundary groove method has been successfully used to measure Gibbs-Thomson coefficient, Gamma, solidliquid interfacial energies, sigma SL, experimentally for transparent materials, binary eutectic, peritectic, monotectic systems, colloidal system, any alloy system, multi-component systems as well as pure materials. It has been shown that the grain boundary groove shapes could be obtained for any system provided that the prepared sample could be held at the evaluated temperature long enough with a very stable temperature gradient. Equilibrated grain boundary groove shapes for binary solid Mg2Si intermetallic phase in equilibrium with liquid AlSiMg ternary eutectic solution have been directly observed with a radial heat flow apparatus. The GibbsThomson coefficient, Gamma, was determined with a numerical method using observed groove shapes. The measured thermal conductivities of the solid and liquid AlSiMg solutions at the eutectic temperature and the temperature gradient in the solid Mg2Si phase were used for the calculation of Gamma. Then sigma SL was determined using the Gibbs-Thomson equation. The grain boundary energy, sigma gb, for the same system was also obtained from the observed groove shapes. The results of the work were compared with the results of the related experimental works.