Origin: Alluvial gravels of the Yellowstone River and its tributaries between Sidney and Billings, Montana, USA

Description: Montana Agate was actually formed in the Wyoming area of Yellowstone National Park. Locals walk the river banks and collect it. There are also a couple suppliers that pay high school kids and pwd's to collect it. They are paid by weight. 

It is a unique rock because it is well known in North America, yet not commercially mined- only surface picked.

Chemical Composition: SiO₂
Grade: Semi Precious
Appearance: Translucent

Inclusions:
Cracks: Some- Montana agate comes from the river. The impacts from other boulders have caused cracks in them. It's just the nature of the stone.
Mineral: Dendrites- Sometimes called "Mosquito Agate" because of small dots. The cracks also allow iron to leach in and bring color. Dendrites as well as banding occur inside Montana Agates.

Cost per Gram: $0.18
Size approximately one piece: 9.5cm x 7cm x 4.5cm
Weight approximately one piece: 341g

Rough is rough. We do our best to grade and describe pieces in the lot, but ultimately, they all differ.