Moss agate

Moss agate is a semi-precious gemstone formed from silicon dioxide.

[1] The field is a clear or milky-white quartz, and the included minerals are mainly oxides of manganese or iron.

The colors are formed due to trace amounts of metal present as an impurity, such as chrome or iron.

[3] Despite its name, moss agate does not contain organic matter and is usually formed from weathered volcanic rocks.

It was originally formed in the Yellowstone National Park area of Wyoming as a result of volcanic activity.