Granite Onyx

Green Onyx MG is likely another specific variant or product name tied to a certain supplier, designer, or collection of onyx stones. The "MG" part of the name could refer to a brand, collection, model, or even a specific feature of the stone, such as its particular color tone, pattern, or origin. Unfortunately, without more context or a known reference to a widespread catalog, "Green Onyx MG" doesn’t appear to be a widely recognized, standard variety in gemological databases or typical onyx classifications.