Manganotantalite is a manganese-rich variety of Tantalite. It is formed when manganese replaces iron.
Manganotantalite is an intense red transparent material that is suitable for cutting into magnificent faceted gems.*
 
This specimen produces the "flash" derived from the magnesium and wheras the clarity is on the lower end of the scale, the size of 10ct makes up for it more then well in this almost impossible to get gemstone.
 
The hardness of the stone sits between 5.5-6.5 and is viable for most jewlery.
 
*https://www.gemdat.org/gem-35838.html