Petrified cycads are fossils formed through the replacement of ancient plant tissue by silica, preserving the unique geometric structure of the original cycad trunk. Collectors prize them for their distinct 'pineapple-like' exterior patterns and intricate internal cellular detail visible in cross-sections.
Is this petrified cycad?
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 petrified cycad with a known reference. Petrified Cycad sits at Mohs 6.5-7, softer than the next harder reference, harder than the previous one.
- 2Name the organismDecide what left the fossil before worrying about the rock. Organism: Cycad-like bennettitalean plant (genus Cycadeoidea). Age: Cretaceous, possibly Jurassic.
- 3Check the preservationPreservation: Petrified by permineralization and replacement. That controls the weight, the hardness and how the piece takes a polish.
- 4Read the lusterHold the specimen under a strong light. Luster: waxy to vitreous.
- 5Match the color rangeCompare against the expected color range: brown, tan, black, gray, yellow.
Often confused with
Petrified Cycad vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside petrified cycad
Minerals reported to co-occur with petrified cycad. 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
- Waxy to vitreous
- Transparency
- Opaque
- Rarity
- Uncommon
- Uses
- Lapidary, Collector, Decorative
- Host rock
- sedimentary strata
- Organism
- Cycad-like bennettitalean plant (genus Cycadeoidea)
- Age
- Cretaceous, possibly Jurassic
- Preservation
- Petrified by permineralization and replacement
Where rockhounds find petrified cycad
1 mapped spotsClassic worldwide localities
- Black Hills, South Dakota, USA
- Wyoming, USA
- Patagonia, Argentina
Field-hunting tip
Where it forms: sedimentary strata. If you start seeing quartz, chalcedony, jasper in float, you are in the right ground. In the U.S., the densest reported localities are in New Mexico. Start trip planning there.
Common questions
How do you identify petrified cycad?+
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Find petrified cycad on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
