What "rational" material can fit on a finger, weighs a few grams or less, is convenient enough to wear everyday, is mostly fungible (yes, diamonds are fungible

What "rational" material can fit on a finger, weighs a few grams or less, is convenient enough to wear everyday, is mostly fungible (yes, diamonds are fungible at the wholesale level), is durable, insurable, and is worth any arbitrary amount you can think of depending on its characteristics? Diamonds are great for their purpose, which is social signaling at a high level.