Banded agate

Banded agate was an ornamental stone used in furniture inlays, inexpensive brooches, and carried as a "soothe stone"&mdash;to be fondled or rubbed between the fingers in order to prevent nervous fidgeting&mdash;by merchants during tense negotiations.

Description
This stone was a form of opaque quartz with striations of brown, red, blue, and/or white. It was normally tumbled or polished smooth and had a waxy feel. A typical stone had a base value of 10 gp.

Powers
A pinch of crushed banded agate powder was traditionally added to sleeping draughts to improve their effectiveness, but there was no solid evidence to justify this practice. Banded agate powder was used as an ingredient in some inks for inscribing spells and in the base mixture for some potions.