You can follow some simple tests to check for your Yellow Sapphire or Pukhraj’s authenticity:
Ask for an authenticity certification
Check for scratches. If you can spot them, it is likely that the pukhraj isn’t pure, as its hardness is comparable with a diamond!
Minor inclusions exist due to natural extraction processes. However, significant marks visible to the naked eye indicate a fake stone.
Check the stone under light and examine it for uneven patches. The presence of such patches indicates that the stone isn’t pure. Yellow Sapphire is totally smooth.