|Damage vs. small||1d3|
|Damage vs. large||1d3|
|Base price||45 zm|
Rubbing an iron item on the touchstone will produce a signature "scritch, scritch" noise, which is the most reliable means of identifying the stone. Rubbing any gem on the touchstone will produce the same noise as the result if you are blind. They can also be identified by price, being the only gray stone with a 45 base price.
A blessed touchstone will immediately identify the gem, as will an uncursed touchstone in the hands of an archeologist or gnome. An uncursed or cursed touchstone will merely distinguish glass from gems, but a cursed touchstone has a 1/5 chance of shattering gems that are rubbed on it..
A touchstone is always generated in the inventory of a jewelery shop's shopkeeper.
Using a touchstone
If the touchstone is blessed or you can use it as blessed, all tested gems will be identified, allowing you to sell them for full price and get the full luck bonus for throwing them to unicorns. Other gray stones and glass can also be identified this way. Using a touchstone in this way identifies the touchstone as well.
If the touchstone is used as uncursed, valuable gems will leave colored streaks (the exact color depending on the gem's color), while glass will leave scratch marks. You may then use your scrolls of identify to formally identify the valuable gems without wasting any on glass. Type-name the glass before discarding it to avoid the need for redundant testing. Uncursed testing will not distinguish gray stones from each other.
Rubbing a gem or glass on a non-touchstone will make colored scratch marks . Therefore rubbing a gem or glass on an unidentified gray stone can identify a touchstone (colored streaks or scratch marks) from other gray stones (colored scratch marks).
"You see <color> streaks on the stone."
- Valuable gem, and this is a touchstone
"You make scratch marks on the stone."
- Worthless glass, and this is a touchstone
"You make <color> scratch marks on the stone."
An unidentified touchstone can be used to distinguish metal objects (scritch, scritch) from non-metal objects, but this strategy is somewhat obscure and of only limited utility. Gauntlets of power and kicking boots are the only items in the game that can be distinguished in this way.
If you are hallucinating, you cannot use a touchstone, no matter what BUC status. You only receive the message "Oh wow, man: Fractals!" This will not identify the gem or touchstone, although it does lead to indirect identification of the touchstone through the message.
In SLASH'EM, touchstones can only be used on gems.
"Gold is tried by a touchstone, men by gold."
- apply.c in NetHack 3.6.0, line 2226
- apply.c in NetHack 3.6.0, line 2196
- shknam.c in NetHack 3.6.0, line 671
- src/apply.c in NetHack 3.6.0, line 2276