Solid Stone

Solid stone can be found while mining and is used in Blacksmithing and Engineering and Jewelcrafting.

Source
Found in mithril veins.

Blacksmithing

 * Solid Grinding Stone
 * Solid Sharpening Stone
 * Solid Weightstone

Engineering

 * Solid Blasting Powder

Jewelcrafting

 * Solid Stone Statue

Other
You need one solid stone to create the Elune Stone using Elune's Lantern from the season quest Elune's Blessing.