Tree Agate Identification Guide

What Tree Agate Looks Like

Tree agate is a white to colorless chalcedony (microcrystalline quartz, SiO2) containing green, branching, plant-like inclusions of manganese and iron oxides called dendrites. Despite the name, these are not fossils or actual plants — they are mineral crystallizations that mimic ferns, moss, or trees.

• Color: Opaque milky white to grayish-white base with green (occasionally brown or black) dendritic markings.
• Luster: Waxy to vitreous on polished surfaces.
• Transparency: Generally opaque (more opaque than translucent moss agate).
• Habit: Massive chalcedony, often cut as cabochons, beads, or tumbled stones; the dendrites form feathery, tree-like patterns.

Field-ID Checklist

1. Check the base color — true tree agate has an opaque white/cream body, not a translucent or banded one.
2. Look for dendrites — green branching, fern- or tree-like inclusions.
3. Test hardness — chalcedony is Mohs 6.5–7; it scratches glass and resists a steel knife.
4. Note the lack of banding — unlike classic agate, tree agate usually lacks concentric color bands.
5. Apply acid — quartz does NOT fizz (separates it from carbonate look-alikes).
6. Feel the surface — smooth, waxy, and hard.

Key Diagnostic Tests

• Mohs hardness: 6.5–7. Scratches glass; not scratched by steel.
• Streak: White.
• Cleavage/fracture: No cleavage; conchoidal fracture typical of quartz.
• Acid test: Inert — no effervescence in dilute HCl, ruling out carbonates.
• Density: ~2.6 (typical quartz).
• Inclusions: Manganese/iron oxide dendrites that branch in a fractal, plant-like manner.

Common Look-Alikes

• Moss agate: The closest relative — but moss agate has a more translucent base and irregular, moss-like (not strictly tree-branching) green/red inclusions. Tree agate is more opaque white and the dendrites are more tree- or fern-shaped.
• Dendritic agate: Translucent chalcedony with dendrites on a clearer base; tree agate is opaque white throughout.
• Plume agate: Has feathery plume inclusions but typically in colorful, translucent chalcedony.
• Dyed howlite or magnesite: Softer (Mohs 3.5) and will be scratched by a knife; veining is not branching dendrites.
• Bloodstone: Dark green with red spots, not white with green branches.

Where It's Found

Tree agate is found in many parts of the world, with significant supplies from India, as well as Brazil, the United States, Madagascar, and Uruguay. It forms in cavities and fractures of volcanic and sedimentary rocks where silica-rich solutions deposit chalcedony and manganese/iron solutions infiltrate along cracks to grow the dendrites.