Uncut opal

Uncut Opal is a members-only item on the OSRS Grand Exchange in the other category.

In-game examine text: "This would be worth more cut."

It has a Grand Exchange buy limit of 10,000 every four hours, a high alchemy value of 12 gp, and item ID 1625.

View on OSRS Wiki

Uncut Opal shows an active flip setup with a margin of +26 gp and 204,122 trades over the last 24 hours.

At the buy limit of 10,000 every four hours, max profit per cycle is about 260.0k gp — high margin with healthy liquidity.