Toughened glass panels used as glazing material in multistory buildings are subject to fracture when they contain nickel sulfide inclusions. The failure mechanism is generally attributed to the significant volume increase related to a polymorphic phase retransformation in nickel sulfide. This investigation exploits the ability of micro Raman spectroscopy to analyze minute inclusions. The technique is able to distinguish between different polymorphs and various stoichiometric forms of nickel sulfide and has the potential to satisfy the need for an in situ, nondestructive analytical technique for the characterization of nickel sulfide inclusions in glass.