Found in mithril veins.
As an ingredient
You need one solid stone to create the using from the season quest Elune's Blessing.
- Patch 9.0.1 (2020-10-13): Item level modified due to level squish, from 35 to 1.
- Patch 6.0.2 (2014-10-14): Stacks to 200, up from 20.