Feather Agate Identification Guide
Identify feather agate by the delicate plume- and feather-shaped mineral inclusions suspended in translucent chalcedony, with tests versus look-alikes.
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What Feather Agate Looks Like
Feather agate is a plume/inclusion agate - translucent chalcedony containing delicate, feather- or plume-shaped mineral growths (often iron or manganese oxides, or chlorite/celadonite) suspended within the silica.
- Color: clear to milky or smoky base with white, red-brown, golden, green, or black feathery plumes.
- Pattern: soft, branching, feather- or fern-like sprays that appear three-dimensional inside the stone.
- Luster: waxy to vitreous; glassy when polished.
- Transparency: translucent (you can see the feathers floating within).
- Form: massive nodules and slabs; the feathers show best on polished surfaces.
Step-by-Step Field-ID Checklist
- Backlight it. Hold to light; true feather agate is translucent and the plumes appear suspended in three dimensions.
- Examine the plumes. Look for soft feathery/branching forms (distinct from straight banding or geometric dendrites).
- Confirm hardness. Scratches glass and steel (Mohs ~7).
- Check fracture. Conchoidal break confirms chalcedony.
- Feel the polish. Cool, dense, takes a high glassy polish.
Key Diagnostic Tests
- Mohs hardness: ~7 (scratches glass).
- Streak: white.
- Cleavage/fracture: none; conchoidal fracture.
- Specific gravity: ~2.6.
- Acid: no fizz (silica, not carbonate).
- No magnetism.
Common Look-Alikes and How to Tell Them Apart
- Dendritic agate: dendrites are flat, two-dimensional, tree-like mineral films along a plane; feather agate plumes are softer, fuller, and three-dimensional within the stone.
- Moss agate: has mossy, irregular green/black blobs rather than ordered feather sprays.
- Plume agate: very closely related (often used interchangeably); plume agate's inclusions are upright plumes, feather agate's are more feather-like; both are inclusion chalcedony.
- Banded/eye agate: shows concentric or parallel banding, not floating feathers.
- Painted/printed fakes: patterns sit on the surface and color pools in cracks; natural plumes are inside the translucent stone.
Where It Is Typically Found
Feather and plume agates occur in many volcanic agate districts. Notable sources include the western United States (Oregon, Texas - e.g., Woodward Ranch plume agate, Nevada), Mexico, India, and Brazil. They form in cavities of volcanic rock where iron/manganese-rich solutions deposited feathery growths that were later enclosed by chalcedony.
Frequently asked questions
What causes the feathers in feather agate?
The feathery shapes are mineral inclusions, often iron or manganese oxides or chlorite, that grew as plume-like sprays in a cavity and were then sealed inside the translucent chalcedony as the agate formed.
How can you tell if feather agate is real?
Backlight it: real feather agate is translucent with feathery plumes suspended in three dimensions, is hard quartz (scratches glass, Mohs about 7), has a white streak and conchoidal fracture, and does not fizz in acid. Painted fakes show only surface patterns.
Feather agate vs dendritic agate: what's the difference?
Dendritic agate has flat, two-dimensional tree-like mineral films along a plane, while feather agate has softer, fuller, three-dimensional feather or plume inclusions that appear to float within the stone.
Is feather agate the same as plume agate?
They are very closely related inclusion agates and the names are often used interchangeably. Plume agate tends to show upright plume-shaped growths, while feather agate shows more feather-like sprays; both are translucent chalcedony with mineral inclusions.
Feather Agate identified by the community
Recent Feather Agate specimens identified with Rock Identifier.
