This Guasha Set is made with obsidian stone.
 
Obsidian is a common black medium and low-grade natural gem, and it is also known as natural colored glaze.
 
As the name suggests, it is a naturally occurring colored glaze.
 
It was formed because volcanic lava rapidly cooled and condensed, with an amorphous structure. 

Obsidian is usually black, but brown, gray, and a small amount of red, blue, or even green obsidian can also be seen.

The advantages of using black obsidian scraping regularly are as follows:
 
 
Dilates capillaries
Increase sweat gland secretion
Promote the excretion of skin waste
Helps improve blood circulation
Remove stasis
Reduce swelling and pain
Brighten the skin, lift and tighten
Make the skin more youthful