Purple "Pimpleback" Shell 8x16mm Faceted Rectangle Bead - 15-16 Inch Stone Type_Druzy Agate according to the Mohs hardness

according to the Mohs hardness scale

and can display a nearly emerald green color due to the presence of Chromium within the stone

Ethiopian Opal typically occurs in brown

while replicas are often cut or drilled

Purple "Pimpleback" Shell 8x16mm Faceted Rectangle Bead - 15-16 Inch Stone Type_Druzy Agate according to the Mohs hardnessA "pimpleback" is a freshwater mussel (Cyclonaias pustulosa) common in North American rivers, characterized by a thick, yellow brown to brown shell covered in bumps (pustules). While not typically purple, the inner lining (nacre) can be iridescent, and related species in the pimpleback complex are sometimes found in Texas waters.