If you have examined these pearls, and have successfully done the tooth test and they do feel gritty when you slide the pearls against the surface of your teeth then chances are pretty good of them being genuine cultured pearls.
More photos of the pearls, check the drill holes and if you can get a close-up photo of the drill holes, attach for appraisal purposes, more photos would provide further evidence to ascertain the authenticity. I'm sure they must be beautiful in real life and deserve the love, and care you are giving them.
Have you examined the pearl clasp which is a wonderful feature of this necklace, to see if there is a signature or any markings? You might need a magnifying glass 10x magnification, or jeweler's loupe to see these markings.
Photos of the pearls and more details including the size of the pearls, the length of the necklace, and do include a close up of the clasp as all the above information including photographic information would be very helpful in making absolutely certain you get the best possible price for this beautiful pearl necklace.
