Saturday, February 04, 2006

Oldies but Goodies--Stromatolites

Stro'-mat'-o-lite) Stromatolite is fossilized blue-green algae. They are some of the oldest known living organisms on earth. Some from Europe date back to about 4.5 billion years ago.

(I was going to put more of the technical stuff here, but Anita-–my trusty editor--said it was a little too dry). Stromatolite is rather common around the world. There are many types of stromatolite but most resemble rounded, layered rock balls or domes. A popular type is the stacked or layered (in cross section) domes. As the algae builds up layers, the older algae on bottom dies off and forms a base for the new algae on top. Stromatolite has a great resistance to change and destruction. We still have them forming on earth today off the Keys in Florida and on the outer edge of the Great Barrier Reef in Australia. They can occur anywhere there is warm water and a place for them to grow. The western US was under water at one time and hence has several places where there is fossilized stromatolite. Wyoming, Nevada, and yes, Utah all have good deposits of stromatolite. The large stromatolite beds in Utah are around the west side of the Great Salt Lake and are now under water again. They are exposed during seasons of extreme drought. The Bird's Eye Rhyolite found in Utah county is not really a rhyolite but a marble and the "eyes" are stromatolites within the marble.

Too cool!

The ones from Wyoming were all but depleted by collectors from the 1940's-1980's. Many large areas that had them are now cleaned out. The reason for the collecting is not that it is important to science but rather it is very attractive when polished. It is a light milk chocolate with darker chocolate bands between the different layers of algae. This rock has always been popular with the fossil collectors and lapidary people alike.

There is now some strong evidence that the Zebra Stone from Australia is also a type of stromatolite or was produced by a stromatolite.

The famous Banded Iron Formation of Wyoming is also part of a stromatolite. It was created when iron-eating algae produced an oxygen rich environment that produced the banded red jasper.

Stromatolites from England & Australia are very common (another clue to the Zebra Stone) and are very attractive. I hope that peaks your interests and brings out the stromatolite collector in you!

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