Two pieces of a really unusual mineral! The basic mineral is andalusite, and in this form when the crystals are sliced a cross of carbon is revealed. The squarish shape is natural, with the cut faces having been polished to show off the crosses better. I think that they can work as bookends, or as a pair of individual specimens. The book is included.
Approximately 9/16 inch (1.4 cm) wide and tall, 5/16 inch (0.8 cm) deep.