Tree Agate

Tree agate is a white to colorless variety of chalcedony (microcrystalline quartz) containing striking green or black branching, tree- or fern-like inclusions called dendrites. These dendrites are not plant fossils but mineral growths, usually of iron or manganese oxides.

It is closely related to moss agate and dendritic agate; tree agate typically refers to opaque white material with dendritic patterns, while moss agate is often more translucent with moss-like inclusions. Strictly, because it lacks the banding of true agate, it is sometimes classed simply as dendritic chalcedony.

Its naturalistic, garden-like patterns make each piece unique and popular in jewelry and decorative lapidary.

Tree agate forms when silica-rich fluids fill cavities, cracks and porous zones in volcanic and sedimentary rocks, hardening into chalcedony. The dendritic patterns develop as mineral-laden water seeps along tiny fractures and precipitates iron or manganese oxides, which crystallize into branching, fractal-like growths.

These dendrites form within or between layers of the chalcedony, creating the appearance of plants frozen in stone, though they are purely inorganic mineral deposits.

Tree and dendritic agate are found in many parts of the world, with notable material from India, Brazil, the United States and Madagascar, often weathered out of basaltic host rocks.

Look for a milky white to grayish translucent-to-opaque stone with green or black branching, fern-like dendrites running through it. Tree agate is hardness 6.5-7, scratches glass, and has a waxy to vitreous luster with a conchoidal fracture typical of chalcedony.

The dendrites are flat, two-dimensional and follow cracks, distinguishing them from genuine three-dimensional plant fossils. Streak is white.

Look-alikes include moss agate (more translucent, mossier inclusions), dendritic opal and plume agate. The key is recognizing the white chalcedony base with mineral dendrites; unlike fossils, the patterns are inorganic manganese or iron oxides. It will not fizz in acid, separating it from carbonate stones.

Tree agate is widely cut into cabochons, beads, spheres and tumbled stones for jewelry and decorative objects, prized for its unique nature-like patterns and durable hardness. Each piece is one of a kind because of the random dendrites.

Like other chalcedonies it takes a good polish and is affordable, making it popular for malas, bracelets and home decor.

Metaphysically, tree agate is associated with growth, stability, abundance and a connection to nature, often marketed as a grounding "stone of plant growth," though these claims are not scientific.