Soul Stone

Sell value
30 Gold

What drops it

 * Shiro'ken Warrior
 * Shiro'ken Ranger
 * Shiro'ken Monk
 * Shiro'ken Necromancer
 * Shiro'ken Mesmer
 * Shiro'ken Elementalist
 * Shiro'ken Assassin
 * Shiro'ken Ritualist
 * Bound Vizu

Common crafting materials

 * 3-4 Granite Slabs

Rare crafting materials

 * 1 Lump of Charcoal

Testing
In a trial of 50 Soul Stones salvaged using a Superior Salvage Kit, 162 Granite Slabs and 6 Lumps of Charcoal were produced. A loss was recorded: for maximum value, just sell them to the merchant.