ive made black pearls with just the oysters.. buuuuuuuut, theres not just one specific moon phase for it..

its very very random. ive made 5 in one stack, and 1 in another, both on full moons.. lol

i use primary tool only (<-lazy)

so pretty much, you just gotta take a bunch at a time, and just throw em to the sky and hope for the best. gl!