Moss agate is an interesting variety of chalcedony, a cryptocrystalline form of quartz. Unlike classic agates, it does not usually contain the typical layering, but is characterized by the presence of dendritic inclusions that resemble moss or tree branches. These patterns are not of organic origin but are due to iron and manganese oxides. Moss agate is most commonly found in translucent to milky white with inclusions in shades of green, brown, black or red.
Its hardness on the Mohs scale is 6.5 to 7, which is the same as that of ordinary quartz. It has a waxy to matt lustre and is semi-transparent to translucent. Significant deposits of moss agate are found in India, Brazil, the USA (especially in Montana, Oregon and Idaho), Madagascar and Russia.