Strontiopiemontite, a new member of the epidote group, from Val Graveglia, Liguria, Italy

Strontiopiemontite, a new member of the epidote group with simplified formula CaSr(Al, Mn, Fe) (sub 3) -Si (sub 3) O (sub 11) O(OH), occurs as small deep red prismatic crystals in the manganese ore deposit of Val Graveglia, Liguria, Italy. Physical properties, including the powder pattern, are similar to those of piemontite. Crystals are often twinned {100}. Crystal structure refinements performed on two separate crystals clearly show that the entry of Sr into the structure mainly occurs on the A(2) site (max. 70%) and leads to a significant increase of the A(2) polyhedron volume as well as the c . sinbeta value.