Silicified fossils are organic remains that have been replaced molecule by molecule by silica during the fossilization process. Collectors should look for preserved cellular structures, rings in wood, or detailed surface textures in shells and bones. They are typically found in sedimentary layers where silica-rich groundwater has permeated organic matter.
Is this silicified fossils?
5-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 silicified fossils with a known reference. Silicified Fossils sits at Mohs 6.5-7 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Silicified Fossils leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Silicified Fossils typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: brown, red, yellow, white, gray, black.
- 5Look at form & habitCrystal system: trigonal. Typical habit: pseudomorph.
Often confused with
Silicified Fossils vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Luster reads vitreous on Silicified Fossils and waxy on Chalcedony.
How to tell apart: Luster reads vitreous on Silicified Fossils and waxy on Agate.
How to tell apart: Luster reads vitreous on Silicified Fossils and waxy on Jasper.
Often found alongside silicified fossils
Minerals reported to co-occur with silicified fossils. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SiO₂
- Mohs hardness
- 6.5-7
- Density
- 2.5-2.7 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Pseudomorph
- Cleavage
- None
- Rarity
- Common
- Uses
- Lapidary, Collector, Decorative
- Host rock
- Sedimentary Deposits
- Typical price
- $5-500 depending on specimen quality and rarity
Where rockhounds find silicified fossils
1 mapped spotsClassic worldwide localities
- Petrified Forest National Park, USA
- Madagascar
- Indonesia
- Argentina
- Egypt
Field-hunting tip
Look in sedimentary deposits country — that is the host setting where silicified fossils typically forms. If you start seeing quartz, chalcedony, goethite in float, you are in the right ground. Field specimens usually show a pseudomorph habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Kentucky — start trip planning there.
Common questions
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Find silicified fossils on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
