Quick answer
Greyed out usually means the current weapon does not support that stone
Support stones use character-wide slots, but Combat, Infusion, and Ability stones are attached to the melee weapon or sidearm side of the loadout. Many are intentionally compatible with only part of the weapon roster. Current player reports
Compatibility checklist
- Check the category: Combat, Infusion, and Ability use different sockets.
- Check melee versus sidearm: a ranged stone will not enter the melee-side slot.
- Equip the target weapon first: the available stone list changes with the weapon.
- Do not assume every Infusion is universal: players specifically report Axatana rejecting several found Infusions. Infusion discussion
What happens when you switch weapons?
Players report that switching to an incompatible weapon can unequip its stones, while returning to the previous weapon restores that weapon's earlier Tarstone loadout. Verify the icons after every switch rather than assuming XP is still reaching the intended stones.
Compatibility also affects Tarcore farming
A stone that fits only one or two weapons can be tedious to level if those weapons are not part of your build. Temporarily equip the supported weapon, fill all compatible unfinished slots, and run a safe XP loop. Do not mistake incompatibility for a broken XP trigger.
Why this is not yet a full compatibility matrix
Third-party matrices currently conflict on stone totals and level counts. We will publish exact weapon-by-stone tables only after direct UI captures or multiple current-version sources support each mapping.