Moss Agate is not banded, and therefore not strictly an Agate in scientific terms; but is included in the Agate family. Agate is a variety of Chalcedony, a mineral of the Quartz family. It is clear to milky white, with dendritic inclusions of manganese or iron that has grown into patterns similar to moss or lichen. Spots of red may occur in some specimens, and occasionally dark green with bluish inclusions.
Montana moss agate is found in the alluvial gravels of the Yellowstone River and its tributaries between Sidney and Billings, Montana. It was originally formed in the Yellowstone National Park area of Wyoming as a result of volcanic activity. In Montana moss agate the red color is the result of iron oxide and the black color is the result of manganese oxide.
photos by RyanVa
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