A stromatoporoid is a member of an extinct group of colonial marine organisms that were major reef-builders from the Ordovician through the Devonian. It typically appears as a layered or mamelon-textured calcareous mass, identified by its distinct grid-like internal structure under magnification.
Is this stromatoporioid?
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 stromatoporioid with a known reference. Stromatoporioid 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. Stromatoporioid leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Stromatoporioid 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
Stromatoporioid vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside stromatoporioid
Minerals reported to co-occur with stromatoporioid. 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
Where rockhounds find stromatoporioid
1 mapped spotsClassic worldwide localities
- Canada
- United Kingdom
- Estonia
- United States
- Czech Republic
Field-hunting tip
Look in sedimentary limestone or dolostone country, the host setting where stromatoporioid 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.
More stromatoporioid photos
Common questions
How do you identify stromatoporioid?+
Where is stromatoporioid found?+
Can I find stromatoporioid in the United States?+
What rocks look like stromatoporioid?+
What minerals are found with stromatoporioid?+
What kind of rock does stromatoporioid form in?+
What is stromatoporioid used for?+
Find stromatoporioid on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
