The only use I can find is a cut opal for Digsite quest.
You can fletch opal bolt tips for a regular crossbow but that’s completely useless because the crossbow is horrible and the bolts can’t even be enchanted.
You can cut them for 15/20/25 xp (O/J/RT) which is 2-3x worse xp than a sapphire.
Even when the Tai Bwo Wannai minigame comes out it’s easy to get 100% favour with any machete and every tier of machete can be bought and traded anyway.
They are used in Digsite and Legends. They were added to the game with Shilo Village and I’m pretty sure the only original purpose was to be trash you get from gem rocks because gem rocks would be way too powerful if they always gave standard gems.
Crafting and Fletching XP.
I wouldn’t toss them because future updates but that’s just me.
Pretty sure you can make bolts from them
are pearl and opal bolts better ranged strength with the crossbow?