|Damage vs. small
|Damage vs. large
Unfortunately, healthstones are always generated cursed. Players picking up an unknown gray stone may want to bag it until they can curse-test it. A cursed gray stone that is not a loadstone is almost always a healthstone: this can be useful as a way to pseudo-identify them.
Unlike luckstones, healthstones are cumulative - two blessed healthstones are better than one. To be precise, you have a health recovery bonus which is 2 for each blessed healthstone in your main inventory, plus 1 for each uncursed healthstone, minus 2 for each cursed healthstone. This bonus is added to your level and constitution when calculating how fast or how much you heal, i.e. if you carry 2 blessed healthstones at level 1 you will regenerate every 7th turn (as at level 5) instead of every 15th, and at level 29 you will regenerate 1d24 HP instead of 1d20 every 3 turns (provided your constitution is 20).
Healthstones are most effective at lower experience levels. In the examples above with two blessed healthstones, the level 1 character is healing over twice as quickly as they usually would, while the level 29 character is healing a mere 20% faster than normal. High-level characters should consider whether the weight of a large stack of healthstones might instead be better used for items that can kill monsters quickly, such as wands of death, as well as for emergency healing items such as blessed tins of nurse meat or potions of full healing.
Mechanics adapted from a spoiler by Eva Myers.