Silicified algae represents ancient cyanobacterial colonies where organic material has been replaced by microcrystalline quartz. Collectors often look for distinct layering or 'cabbage head' growth patterns known as stromatolites which indicate the original biological structure.
Is this silicified algae?
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 algae with a known reference. Silicified Algae 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: Stromatolite: layered structures built by microbial mats, especially cyanobacteria.
- 3Check the preservationPreservation: Silicified. That controls the weight, the hardness and how the piece takes a polish.
- 4Read the lusterHold the specimen under a strong light. Luster: waxy.
- 5Match the color rangeCompare against the expected color range: tan, brown, gray, white, black, red.
Often confused with
Silicified Algae vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside silicified algae
Minerals reported to co-occur with silicified algae. 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
- Transparency
- Opaque
- Rarity
- Common
- Uses
- Lapidary, Collector, Decorative
- Host rock
- sedimentary carbonate rocks
- Organism
- Stromatolite: layered structures built by microbial mats, especially cyanobacteria
- Preservation
- Silicified
Where rockhounds find silicified algae
1 mapped spotsClassic worldwide localities
- Wyoming, USA
- Western Australia
- Morocco
- Utah, USA
- Canada
Field-hunting tip
Where it forms: sedimentary carbonate rocks. If you start seeing calcite, dolomite, quartz in float, you are in the right ground. In the U.S., the densest reported localities are in Wyoming. Start trip planning there.
Common questions
How do you identify silicified algae?+
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Can I find silicified algae in the United States?+
What rocks look like silicified algae?+
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Find silicified algae on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
