Moss agate is a form of chalcedony (microcrystalline quartz) characterized by translucent to milky chalcedony with dendritic or filamentous inclusions that resemble moss, trees, or ferns; these inclusions are typically composed of iron or manganese oxides and occasionally chlorite, creating green, brown, black, or reddish patterns suspended within a clear to white matrix. It forms when silica‑rich hydrothermal fluids or silica gel fill cavities and fractures in host rocks (commonly volcanic or sedimentary), trapping mineral impurities that crystallize as dendrites during slow cooling; nodules, veins, and botryoidal masses are typical habits. Moss agate is found worldwide, with notable occurrences in India, Brazil, Uruguay, the United States (Montana, Oregon), and parts of Europe and Asia.

In metaphysical and crystal‑healing traditions, moss agate is associated with grounding, growth, and renewal—often used to promote emotional balance, attract abundance, and support new beginnings or agricultural and gardening endeavors. It is thought to encourage patience and perseverance, enhance connection to nature, and stabilize mood by calming anxieties while stimulating creativity and optimism.