Opal dust is just that-- leftovers from cutting and polishing. Triplets and doublets include a thin slice of natural or lab-created stone, with a quartz cover for protection, and in the case of triplets, a black stone backing of some sort. Dust is dust. For me, anything less than 1 or 2 mm is what I call OTF (off the floor), and anything smaller than that is useless! I use OTF to suspend in solutions to use as snow-globe type ornaments and pendants. Nature'sJewelry.com has opal dust jewelry. Take a look.