perlas, a question for you: Can you always detect which GSS are dyed?
Are there always dye concentrations? And if not, what else gives them away as being dyed?
One is the color. Some dyed GSS have colors that doesn't seem right. And you are correct. If the pearl have pits, there can be dye concentrations.
However, there are now GSS pearls that are irradiated, according to the sellers. Pearl experts here, you are more than welcome to give us info! If the pearl is perfect, it is difficult to detect since there are no pits to give them out and also irradiation have no concentrations. They look like naturals. Thus, I am very wary with the deep goldens. In fact there are beaded FWPs that are irradiated golden and they do look like GSSPs. Even if you look at the bead hole, the irradiation goes deep into the pearl and it doesn't help. Moreso, the enhanced ones are light yellows or ugly shade of yellows so the inside of the beadhole will also look yellow so it's hard to tell.
I am very cautious I only buy pearls from my trusted sellers who disclose to me what is enhanced and what is not and who I know has supply coming from Mindanao or Palawan. Anything that is bought in Hongkong and Japan has a risk of being enhanced, although the natural colored quality GSSPs are sold at the Hongkong trade shows. Pearls from the Philippines and processed outside the country. I only take ones the have not gone out of the country because so far, the Philippines does not have the capability to enhance GSSP without trace of enhancements because there is no local technology for that.
Note that natural color GSSPs are not really common, so if one is buying loose, one can check the entire lot, it will be mixed with champagnes and a couple or so will have darker colors with some bicolored with whites. That is from a natural local lot.