Gray stone

A gray stone is one of a flint stone, loadstone, touchstone, luckstone, whetstone (SLASH'EM) or healthstone (SLASH'EM). Distinguishing these is fairly easy, as follows.

Identification

The loadstone can be distinguished by attempting to kick it when it is on the ground; unless your character is very strong the loadstone will not move and produce a "Thump!" instead. If you accidentally pick up a loadstone, #name it so that you'll recognize another one when you see it.

A cursed stone that isn't a loadstone must be a healthstone, unless it came from a bones pile.

Rubbing an iron item on the touchstone will produce its signature "scritch, scritch" and can be identified through this. If you rub a gem on a blessed touchstone, both the gem and the touchstone will automatically be identified. Gray stones count as gems in this context.

Exploit

A somewhat dubious way of distinguishing flint stones from luckstones is attempting to name them "The Heart of Ahriman"; if the stone is a luckstone your hand will slip as it is not possible to name the base item of an artifact after its artifact. This behavior is sometimes viewed as unethical and can be frowned upon in some circles. You can also use enlightenment to determine whether you are carrying a luckstone.

Price Identification

Gray stones can be distinguished by price identification: the base price of a luckstone or healthstone is 60 zorkmids, a touchstone is 45 zorkmids, and a flint stone or loadstone is 1 zorkmid.