I have spent quite a bit of time looking at natural Persian Gulf pearls. They are known for their luster and rightfully so. Most of them have a wonderful golden shade to them, but they can also be white and darker colors like black, but black is quite rare. The Pinctada radiata oyster they grow in is quite small and the pearls tend to be on the smallish side, with seed pearls being the most common.
One of the most gorgeous necklaces I have ever seen was of rare large Persian Gulf natural pearls. I felt honored when it was taken from the safe and put on my neck. Items like that are almost priceless.