gemstone
Montana Agate
Silicon Dioxide (Chalcedony with manganese oxide inclusions)
AI-generated identification · may be incorrectMohs hardness of 6.5 to 7. Color ranges from transparent to yellowish-brown with characteristic black dendritic inclusions. It exhibits a waxy to vitreous luster and a cryptocrystalline structure with no cleavage.
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Physical properties
Mohs hardness of 6.5 to 7. Color ranges from transparent to yellowish-brown with characteristic black dendritic inclusions. It exhibits a waxy to vitreous luster and a cryptocrystalline structure with no cleavage.
Formation & geological history
Formed via the deposition of silica-rich groundwater within cavities of Tertiary-aged basalt flows, roughly 50 million years ago.
Uses & applications
Extensively utilized in lapidary arts, wire-wrapped jewelry, cabochons, and highly prized by rockhounds and mineral collectors.
Geological facts
The distinct black tree-like patterns inside the stone are caused by trapped manganese or iron oxide dendrites. It is the official gemstone of the state of Montana.
Field identification & locations
Easily identified by its translucent golden-brown body and dendritic inclusions. Commonly found in the alluvial gravels of the Yellowstone River in Montana.
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