Some gems, like opal, are highly coveted but rare to find, much less in the sizes and quality people dream of owning. Synthetic, or laboratory created jewels, offer you the best of both worlds. You get the beauty of a beloved, rare gemstone, but at a budget friendly price. The term synthetic refers to a man-made material with a natural counterpart. The synthetic crystal replicates the chemical, optical and physical properties of the natural crystal with little or no variation.