Discovering the authenticity of a natural unheated yellow sapphire weighing 21.54 carats starts with examining its GIA  report. This report details key aspects including carat weight (21.54 ct), shape (octagonal), measurements (15.71 x 13.42 x 10.89 mm), yellow color grade, and modified brilliant cut. It also notes clarity (very eye clean) and treatment (heated). For deeper insights into its quality and value, consulting a certified gemologist is recommended. GIA reports are highly respected in the industry for their accuracy, ensuring confidence in the authenticity of gemstones like this remarkable yellow sapphire.