Pearls are formed when an irritant enters the shell of a mollusk. The mollusk then secretes thousands of very thin concentric layers of nacre, a secretion of calcium carbonate (aragonite and conchyolin). Mabé or "blister" pearls occur when the irritant and subsequent layers of nacre attach to inside of the shell of the mollusk.
Around each of the unborn pearl fetuses, I have painted little daisy petals and leaves in nail polish. Dangling from the top of the shard of shell are two tiny "rice" pearls which will bounce against the shell when worn, making the most angelic, beautifully soft jingle, a call to springtime if you listen carefully!