Well, see, that's the thing! That's the answer. Sun Stone. You win! But your reckless guessing makes it a tarnished victory! Minus Points for you, Mister. Mega Minus Points. I'd like to think that, though your victory is sure, the Most Fiendish Riddle took a piece of you with it.
The sun is the oldest object in a solar system, and of course it's bold and eye-catching. Stone is well known for its symbolic qualities of both solidity and stolidness. When one is high on drugs they might be described as "stoned." And, of course, my favorite part: A "clove" is an old English unit of weight equal to seven pounds, so two cloves would be a stone. (That's the British connection.) Zephira was onto it, but she was using the wrong value: A clove can be either seven pounds or eight pounds depending on the context.