An agatized fossil is a biological remain such as coral, bone, or shell, preserved through the replacement of its original structure by microcrystalline silica. Collectors look for high translucency and well-preserved morphological detail. It occurs in sedimentary deposits where silica-rich groundwater has permeated the specimen over millions of years.
Is this agatized fossil?
4-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch agatized fossil with a known reference. Agatized Fossil sits at Mohs 6.5-7, softer than the next harder reference, harder than the previous one.
- 2Check the preservationPreservation: Agatized: silica-rich fluids replace the original material. That controls the weight, the hardness and how the piece takes a polish.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: brown, red, yellow, white, gray, multicolored.
Often confused with
Agatized Fossil vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside agatized fossil
Minerals reported to co-occur with agatized fossil. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Mohs hardness
- 6.5-7
- Density
- 2.6-2.7 g/cm³
- Luster
- Vitreous
- Transparency
- Translucent
- Rarity
- Common
- Uses
- Lapidary, Collector, Decorative
- Host rock
- sedimentary strata
- Preservation
- Agatized: silica-rich fluids replace the original material
Where rockhounds find agatized fossil
3 mapped spotsClassic worldwide localities
- Arizona, USA
- Madagascar
- Brazil
- Indonesia
- Patagonia, Argentina
Field-hunting tip
Where it forms: sedimentary strata. If you start seeing quartz, calcite, pyrite in float, you are in the right ground. In the U.S., the densest reported localities are in Tennessee, Georgia. Start trip planning there.
Common questions
How do you identify agatized fossil?+
Where is agatized fossil found?+
Can I find agatized fossil in the United States?+
What rocks look like agatized fossil?+
What minerals are found with agatized fossil?+
What kind of rock does agatized fossil form in?+
What is agatized fossil used for?+
Find agatized fossil on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
