Abstract: The Huanggangliang, Inner Mongolia Fe-Sn deposit is located in the southern part of the Daxing'anling polymetallic metallogenic belt. It is a typical skarn polymetallic deposit. The mineralogical characteristics and colouring mechanism of grossularite and andradite samples from the deposit are systematically investigated by electron-prob and spectroscopy, which provides a certain amount of research data for the further understanding of the mineralogical characteristics of garnet in skarn-type deposit. The result indicates that the garnet samples contain a small amount of almandine, spessartite and a tiny amount of pyrope, with Cr³⁺, Fe³⁺, Mn²⁺ elements. The Raman spectrum analysis suggests that there are mixed-phases in the grossularite and andradite according to Si-O_Bend bridging oxygen vibration. UV-Vis spectra show that the strong absorption peak of 370-380 nm is caused by electron transition of Cr³⁺, and 420-430 nm and 470-480 nm are often brought on by electron transition of Mn²⁺, and the absorption in the green region of 550-580 nm is caused by the d-d electron forbbiden and the transition of Fe³⁺.