The usage of Kröger-Vink notation eliminates various other conceptual reaction prospects due to necessity of each charge and site harmony. Certification: The existence of a reputable gemological certification from a reliable and recognized gem laboratory provides reliability and assurance to the standard of yellow sapphire or any other gemstone. Or https://www.tumblr.com/thegemjournal/759696203354128384/understanding-the-unique-characteristics-of-yellow?source=share