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.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Petrified Cycad leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Petrified Cycad typically shows a waxy to vitreous luster.
- 4Match the color rangeCompare against the expected color range: brown, tan, black, gray, yellow.
- 5Look at form & habitTypical habit: massive.
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
- Chemical formula
- SiO₂
- Mohs hardness
- 6.5-7
- Density
- 2.6-2.7 g/cm³
- Streak
- White
- Luster
- Waxy to Vitreous
- Transparency
- Opaque
- Crystal habit
- Massive
- Cleavage
- None
- Rarity
- Uncommon
- Uses
- Lapidary, Collector, Decorative
- Host rock
- Sedimentary Strata
- Typical price
- $20-300 depending on size and detail
Where rockhounds find petrified cycad
1 mapped spotsClassic worldwide localities
- Black Hills, South Dakota, USA
- Wyoming, USA
- Patagonia, Argentina
Field-hunting tip
Look in sedimentary strata country — that is the host setting where petrified cycad typically forms. If you start seeing quartz, chalcedony, jasper in float, you are in the right ground. Field specimens usually show a massive habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in New Mexico — start trip planning there.
Common questions
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Find petrified cycad on the map
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