As its name might suggest, ruby-in-zoisite is a metamorphic rock comprised of intergrown microcrystalline masses of pinkish-red to red ruby and green zoisite. However, pargasite may also be present in the form of very dark green, almost blackish crystals. Like most opaque ornamental rocks, ruby-in-zoisite is usually fashioned into cabochons, beads, small carvings and irregular polished forms, with the material’s relative abundance and affordability also occasionally allowing for it to be used to produce larger items as well.

Ruby-in-zoisite was first discovered in the Arusha region of northern Tanzania during the 1950s, and this remains its only known source locality. The material is sometimes referred to by its alternative names of “Tanganyika artstone” and “anyolite”, with the latter having been derived from the local Maasai word for “green”.