You are bidding on a single crystal tumblestone, each stone differs in size so we've added a UK Penny piece to the picture to show scale (a penny is 20mm in diameter)  the picture shows stones from the batch that is currently for sale.  As each piece has it's own unique markings, the item received may differ slightly from those shown in the photograph.

Chiastolite, also known as Cross Stone, is a very rare variety of Andalusite, an aluminum nesosilicate mineral with crossed shaped inclusions of black Graphite and Carbon. The cross can only be seen when this mineral is sliced, though it does run throughout the entire stone. This mineral was first mentioned in a 1648 book titled “De Gemmis et Lapidibus”, but was officially recorded in 1754 by José Torrubia. Chiastolite only has three active localities which include central Massachusetts (USA), Asturias, Spain, and the Bimbowrie Conservation Park in Olary Province, South Australia, Australia