Answered By: Aprille Nace
Last Updated: Sep 17, 2016     Views: 12

The term for this type of inclusion is "Sulphide."

I have attached bibliographies that cover historical information about sulphides and some technical information.

The following websites offer some information about techniques:

Websites:
http://www.dragonbeads.com/sulphides.html
http://users.ticnet.com/mikefirth/sulphide.htm
http://www.dragonbeads.com/sulfmold.html