Following a feasibility study of computer-aided gem testing, which resulted in a student level gem identification program, the author has developed a professional version containing data on over 200 gem materials and gem simulants. The program sections include Gem Identification (using test inputs for refractive index (RI) values, optic sign, specific gravity (SG), etc. ), Gem Data Tables (arranged in alphabetical, RI, and SG order), Gem Data Comparisons, Gem Data Pages, and Gem Calculations (for determinations of SG, reflectivity, critical angle, and Brewster angle). This type of computer program provides rapid access to gem constants and characteristics, and can assist the less experienced gemologist by identifying unfamiliar or rare stones and indicating the various alternatives. -- AATA