Black Mother of Pearl / MOP 24-29mm handmade flower beads (ETB00359) Bryozoan Coral Black is caused by manganese

Black is caused by manganese

Chaorite is strictly massive in nature

5x4mm (47 PCS)

dark brown with some black and white

Radiolarite or radiolarian chert is a high silica sedimentary rock which may be considered a variety of chert

Black Mother of Pearl / MOP 24-29mm handmade flower beads (ETB00359) Bryozoan Coral Black is caused by manganeseMother of pearl, is an organic inorganic composite material produced by some molluscs as an inner shell layer; it is also what makes up the outer coating of pearls. It is strong, resilient, and iridescent. Mother of Pearl is found in some of the more ancient lineages of bivalves, gastropods, and cephalopods. However, the inner layer in the great majority of mollusc shells is porcellaneous, not nacreous, and this usually results in a non iridescent