Trope-a-Day: Gem Heart

Gem Heart: Truth in television where silicon-based or carbosilicate lifeforms are concerned, although while some make use of gem-like structures (say, the galari, who even look like cut gems due to their crystalline structure) one is equally, or even more likely, to find Rock Heart. Or plain old crystalplasm.

Otherwise, mostly seen as things like the trope-page-mentioned gizzard stones.