Ruby zoisite is a relatively rare material from Northern Tanzania.
It's believed to have formed during the Neoproterozoic era.
This geological period spans from approximately 1,000 million years ago to 541 million years ago.
Due to the difference in hardness of the minerals zoisite and corundum, ruby zoisite can be difficult to cut.
It's also known as ruby 'in' zoisite and anyolite.
'Anyolite' comes from the Maasai word for 'green'.
The Maasai tribe work some of the smaller ruby zoisite mines in the Arusha region of northern Tanzania.
