rareESSENCE essential oils are subject to stringent, advanced-scientific testing to verify the quality, potency and purity. This testing and evaluation includes; GC – MS (Gas Chromatography and Mass Spectrometry) Analysis, Specific Gravity, Refractive Index, Optical Rotation, Relative Density and Solubility.After the sample passes the scientific analysis, the final test is the “Odor Evaluation” conducted by our Certified Aromatherapists. Only the finest oils become rareESSENCE Essential Oils and make it into our products.