Datolite

Datolite occures in the copper deposits of the Lake Superior region of Michigan as a secondary mineral in mafic igneous rocks often filling vesicles along with zeolites in basalt.  Unlike most localities throughout the world, the occurrence of datolite in the Lake Superior region is usually fine grained in texture and possesses colored banding.  Much of the coloration is due to the inclusion of copper or associated minerals in progressive stages of hydro-thermal precipitation.  

The datolite from the Keweenaw displays in many colors and every piece is unique to the immediate area it comes from and its during the stages of hydro-thermal precipitation, when the different elements are mixed to create the amazing colors datolite displays.