51g Chiastolite (Andalusite) "Cross Stone", Polished One Side

Chiastolite is a variety of andalusite (An aluminosilicate) that forms at low to medium temperatures as stones like shale are exposed to contact metamorphism. The name is derived from the Greek word "chiastos" which means cross. This was a popular stone in 16th century Spain amongst religious pilgrims. This specimen is from Madagascar.

The "cross" shape on the polished portion is the result of graphite (carbon) inclusions in the stone. Chiastolite is one of the most fascinating "trapiche" minerals in that it is not symmetrical. The word is pronounced with a strong "k".