Do gemstones have GIA certifications like diamonds do?

I have a lot of diamond jewelry, and whenever I buy diamond jewelry, I always ask for the diamond certificate to make sure the diamond's specifications are up to par. I was recently buying a pair of ruby earrings for my granddaughter's birthday (it's her birthstone), and I asked to see the grading report, but the jeweler said there wasn't one. He insisted that precious gems don't have certifications, only diamonds do. Is he trying to bamboozle me?