Blue Copper Turquoise w Blue Topaz Sterling Silver EarringsTwo distinct blues in a single pairthe matte opaque depth of Turquoise beside the clear faceted brilliance of Topaz. Blue Copper Turquoise is a copper aluminum phosphate (CuAl6(PO4)4(OH)84H2O), Mohs 56, its color coming from the copper content in the mineral structure; the matrix veining visible across the stone's surface is the host rock it formed within. Blue Topaz is a fluorine bearing aluminum silicate, Mohs 8, faceted here to maximize its high