Mahogany Obsidian is a naturally occurring form of glass created from quickly cooled lava with traces of Hematite or Iron. We collected a large amount in southern Utah in late 2019.  There are some subtle brown bands running through the stone.  

This stone was wrapped with 22 gage Argentium wire, which is a tarnish resistant sterling silver alloy that does not contain nickel.  Some folks are allergic to nickel so I elected to switch to Argentium in addition to its anti-tarnish properties.