Obsidian, a natural volcanic class, is historically popular for carvings because it can be polished to highly reflective surfaces. It was often used for dark mirrors to aid the observer in the examination of their true inner self. Average sizes (actual measurements may vary) 2.5cm (1in), 3cm (1.2in), 4cm (1.6in), 7cm (2.8in), 10cm (4in)
Wooden sphere stand of similar size included.