Obsidian

Obsidian is a naturally occurring volcanic glass (like rhyolite) composed of silicon dioxide. Its natural color goes from gray to deep black, and it has a density of 2.4.

Obsidian Roll-On has been used in China for thousands of years as a massage tool, for its anti-aging properties. It appeared a lot more recently in Occident, where it is used in holistic treatments and skincare routines as a lymphatic drainage tool. 

Obsidian properties: boost blood circulation, promote healing and reduce muscular tensions. It is also said to repel bad energies and help find balance.