[member="Darlyn Excron"], Well Most yellow crystals are synthetic, or if they are natural, they are either Dantari Crystals, or a very rare one from Ilum.
So I would consider them rare as well. Silver ones are rare because that would be either the Halycon crystals, or a Dragon pearl. However, synthetic crystals have been made that are white/silver as well. Made one like that on my alt account of Xander Carrick.