The use of Kröger-Vink notation gets rid of many other conceptual response possibilities as a result of requirement of both cost and site balance. Certification: The existence of a credible gemological certification from a highly regarded and acknowledged gem laboratory provides credibility and assurance to the caliber of yellow sapphire https://www.tumblr.com/thegemjournal/759696203354128384/understanding-the-unique-characteristics-of-yellow?source=share