|moss agate from Indonesia|
Moss Agate is not banded, and therefore not strictly an Agate in scientific terms; but is included in the Agate family. Moss agate is a semi-precious gemstone formed from silicon dioxide. 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. The field is a clear or milky-white quartz, and the included minerals are mainly oxides of manganese or iron.
The alternative name " Mocha stone" Or "Mocca Stone" comes from the Arabian city of Mocha in Yemen, which was an ancient source for the gemstone.
Despite its name, moss agate does not contain organic matter and is usually formed from weathered volcanic rocks. The colors are formed due to trace amounts of metal present as an impurity, such as chrome or iron. The metals can make different colors depending on their valence (oxidation state).
While moss agate isn't strictly an agate because it's not banded, the stone does have the same chemical composition and intriguing patterns of agate. Moss agate is a variety of chalcedony, belonging to the quartz family, and is often found as fragments from weathered volcanic rock formed in fissures or as pebbles rather than in traditional agate layering.
The spreading moss-like dendritic inclusions you see in moss agate are mostly oxides of manganese or iron, and the colors vary depending on trace amounts of minerals or metals present, such as chrome. Some moss agate on the market can be dyed to improve overall color. Moss agate is chiefly found in India, Brazil, Uruguay, central Europe and the western United States.
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