Akoya oysters building layers of nacre on clam shell beads from Mississippi.

Just to clarify: They are not clams, they're various specie of Freshwater mussel. The clams that you are referring to are the endangered T. Gigas- the giant saltwater clam's shells are used for Chinese Freshwater mussel nucleation, they produce the now infamous Fireball pearls. The shells are also not very well-suited to being used as bead-nuclei because the specific density does not match that of the outer nacre layers. The internal bead will expand and contract at a different rate than that of the nacre in response to external temperature variation, causing splits and cracks in the pearls.

On another note, I am quite interested in hearing about your tour, and will be looking forward to your updates! The junta has many horrible deeds rightly attributed to them, I agree- I am just not 100% about boycotting the efforts of small farmers and miners in the region. Most of the fine rubies that we see on the market today have in fact been smuggled out of Burma (ok, ok Myanmar); they are the miners only hope for survival. If you want to hit em where it hurts, boycott all JADE products- most of the regime's money comes from the exportation of fine Burmese Jade.