Onyx. Chalcedony in parallel layers of different shades of color. It is used for making cameos, the figure being cut in one layer with the next layer as a background. It is stained black and used to make mourning jewelry.
“Christ was like us in our nature, but not in our blemishes; he had our flesh, but without the least stain of imperfection; he had the likeness of sinful flesh, but there was not any sin in him.”
–Stephen Charnock, Discourses on Christ Crucified