Along a distance of more than 1000 km the banks of the Yellowstone River are offering possibilities for collecting the “Montana Agate”.
This transparent to translucent type of agate is characterized by a pale whitish colour in combination with interesting black inclusions (Mangenese-oxide). These agates are waterworn and usually completly rounded pebbles.
The inclusions are following fractures or porous layers of chalcedony. If these inclusions are giving an imagination to the viewer - such as landscapes, trees, bushes ... - they are highly desired and sometimes very high priced.
Sometimes the Montana-agates are showing the Iris-Effect in very thin cut (>2,5 mm) slabs.”Water-Level-Agates” are unusual for this type of agate.