Gemstone

I particularly like the first 3 stanzas of this. All those nots I rather feel the second half rather looses its way in trying to liken you to an undefined gem. I wonder, might it be better to have two similies, the second likening you to (eg) a delicate insect made from fine gold threads or a flower (real not made from gems) or quicksilver that is fluid and hard to contain. I'm just thinking aloud here...