This reminds me of a Christmas present my daughter gave me a few years ago. My son asked her what she was giving me and she replied "A box of rocks." to which my son said "I get it. They're to replace the ones that have fallen out of her head!" Actually, they were very nice geode bookends.
I would say opal best describes me. The white ones. Can't see through them, but you know what they are. Sometimes I flash in blues and greens, sometimes in reds and pinks. I am soft, I need to be kept well-oiled and can get crazed if I don't take care!