Stromatoporoids are an extinct group of colonial marine organisms that were major reef-builders from the Ordovician to the Devonian periods. They typically appear as layered or mamelon-textured calcareous masses that are easily identified by their distinct grid-like internal structure when viewed under magnification.
Is this stromatoporioids?
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 stromatoporioids with a known reference. Stromatoporioids sits at Mohs 3-5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Stromatoporioids leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Stromatoporioids typically shows a dull luster.
- 4Match the color rangeCompare against the expected color range: tan, brown, gray, white.
- 5Look at form & habitTypical habit: massive, laminar, columnar, hemispherical.
Often confused with
Stromatoporioids vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside stromatoporioids
Minerals reported to co-occur with stromatoporioids. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Mohs hardness
- 3-5
- Density
- 2.6-2.8 g/cm³
- Streak
- White
- Luster
- Dull
- Transparency
- Opaque
- Crystal habit
- Massive, Laminar, Columnar, Hemispherical
- Cleavage
- None
- Rarity
- Common
- Uses
- Collector, Educational, Decorative
- Host rock
- Sedimentary Limestone or Dolostone
- Typical price
- $5-100 depending on size and preservation
Where rockhounds find stromatoporioids
1 mapped spotsClassic worldwide localities
- Canada
- United Kingdom
- Estonia
- United States
- Czech Republic
Field-hunting tip
Look in sedimentary limestone or dolostone country — that is the host setting where stromatoporioids typically forms. If you start seeing calcite, dolomite, quartz in float, you are in the right ground. Field specimens usually show a massive, laminar, columnar, hemispherical habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Iowa — start trip planning there.
Common questions
How do you identify stromatoporioids?+
Where is stromatoporioids found?+
Can I find stromatoporioids in the United States?+
How much is stromatoporioids worth?+
What rocks look like stromatoporioids?+
What minerals are found with stromatoporioids?+
What kind of rock does stromatoporioids form in?+
What is stromatoporioids used for?+
Find stromatoporioids on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
