A greenish stone glimmering from various precious minerals. It may be used to transport you quickly once to caves vast distances away.
Farwalker stone allows you to teleport once to a distant location that has been set inside some mine.
To set the place that you wish to teleport to, activate the stone and right click a vein tile, then choose 'Set teleport marker'. Thereafter you can teleport to that location by activating the stone, right clicking on the ground and choosing 'Teleport'. You will be taken there instantly and the stone will disappear from your inventory.
Used on a vein tile only while underground. Warning : This seems not to work on created (transmuted) veins. You can set the location, but it will not teleport you. This is being tested to verify the situation.