• A large round pseudo-stromatolite with the flat face covered in many ripply concentric rings of layering. One edge of the piece curls up. The piece has a light yellow-tan coloration.
  • Angled view of the piece showing the sides are smooth and straight with two round nubbins sticking out.
  • Side-view of the specimen, showing the sides are straight and bottom is flat so the piece is shaped like a large lopsided cake.
  • Side-view of the piece upside-down, with slightly lumpy texture to the sides and base.
  • View of the underside of the piece, partially covered in flaky light matrix.
  • Another view of the front face of the piece, which exhibits very good layering, with one flat patch at the bottom.
  • Detail view with more angled lighting emphasizing the rings with shadows. The piece has a grainy sandstone texture and deep, well-formed rings.
  • The specimen phosphorescing a light yellow-green color in the dark.
  • Scale image of the piece on a measuring mat, measuring approximately seven inches across and a bit under seven inches wide.
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Pseudo-stromatolite, extra large

Pseudo-stromatolite, extra large

$54.00 USD
$54.00 USD
Sale Sold out
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Locale: Morocco

Approx dimensions: 7 x 6.25 x 4"

Approx weight: 9 lbs 12.5 oz


A stromatolite is a sedimentary fossil structure made by prehistoric bacteria colonies, typically cyanobacteria. Stromatolites in fact are still living and forming in some parts of our world today, including Australia, and are among the earliest forms of life—and fossils—on our Earth.

The fossils form in shallow water conditions of lakes or salt water shores. First, cyanobacteria grow in microbial mats. Minerals like calcium carbonate precipitate (crystalize from the water) onto the surface of the mat. The bacteria acts as a glue, cementing it all together with sedimentary debris. Layers build up over time like a bacterial pearl; the name “stromatolite” appropriately means “layered rock” in Greek.

This, however, is not a stromatolite. They are commonly believed to be stromatolites, and you will more often than not see them sold under that name and description. More accurately, they are concretions formed out of beautiful tones of red sandstone material. These sandstone concretions form in a manner similar to stromatolites, but minus the aid of bacteria: mineral-rich waters precipitate barite which binds with sand to form concentric layers around a nucleus. It is a relative of the barite desert rose, which grows clusters of round blade-like ‘petals.’

This specimen makes for an inexpensive large piece to add to your mineral collection or use as decor around the home. While pseudo-stromatolites typically have a rounded or conical back, this specimen is wide and flat like a lopsided cake with round nubbins attached to the side.

UV reactivity Many pseudo-stromatolites from Morocco have faint to moderate white fluorescence and light yellow-green phosphorescence under 365 nm UV light. This specimen has good reaction, with phosphorescence apparent.
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