Serpentine stone

Serpentine stone was the name given to a wide variety of minerals including williamsite, ricolite, picrolite, taxoite, and bowenite. It was used for carving, furniture inlays, and building facing. Outside the Realms it was known as verde antique.

Description
This greenish material was found in large deposits and could cut be into thin slabs for ornamental screening, used as an inlay, or as ornamental surfacing. A typical price was 3 gp per pound (6.6 gp/kg).

Powers
This stone was used for in the creation of the figurine of wondrous power known as the serpentine owl. Certain varieties of this mineral shared the same protective properties as the gem-quality serpentine, i.e., it granted a one-time boon of a resist fire and a resist cold spell, disintegrating to dust after reacting to one each of extreme cold and extreme heat. Only skilled jewelers, miners, and spellcasters with experience working with this stone could determine if a particular sample had this magical property or not.