Comparison of glass particles by the forensic scientist is routinely accomplished by measuring some physical properties. Direct comparison of densities ϱ and refractive indexes (ͻC, ͻD, and ͻF being the refractive indexes determined at 6563, 5893, and 4861 nm, respectively) are the most widely used physical measurements because of convenience, reproducibility, sensitivity, and applicability to small sample size. Traditionally, if the physical comparison showed significant difference, it was concluded that the two glass samples could not have had a common origin. Conversely, when the specimens were not distinguishable the forensic scientist reported these samples as possibly having the same origin. Generally he did this without giving consideration to another variable-elemental composition of the samples.