Sieber Agate tumbled from Germany.

Sieber Agate is basically no agate but a glassy copper sludge that these copper smears formed when winning copper from copper ore through high heat. That the material has melted is still good to see. The material is glassy with sometimes a blue tint. Found in Siebertal, Harz, Germany. The color is pretty blue and it is rare. Sieber agate is a very unique lapidary material from Germany, which displays a subtle play of swirling patterns of dark electric blue. Although it is sold as “agate” it is technically a glassy slag left from an ancient copper smelting process over 1400 years old. It characteristically contains numerous pinhead sized vesicles and works up much the same as obsidian