Well I learned something new today.
So the 30k Fist novels often mention the icon being made of "polished jet" but I haven't actually seen Jet so I decided to look it up and found out it's made from super compressed wood.
It's also different than actual gems in how it interacts with light. Neat.
It's probably one of the funnest gemstones to hold because, since it's made of coal, it is way lighter than your brain thinks it is since rocks tend to be denser. Also where the term Jet Black comes from.
It's interesting that Imperial Fists went with decorative elements in their armor but chose one of the least valuable of them to work with. Jet service studs are also a thing mentioned.
