Small
These are really too small to be able to catch the full effect of these opals. The opals, if you look closely, do have some "fire" highlights (the "sparkle") but the size of these makes that nearly impossible to see. They just look like a flat blue color unless you get up to within a few inches.  I'd recommend something twice this size in order to see the opal's sparkle more easily.
Rating: 3 stars