Wednesday, January 23, 2013


Coprolite is the fossilized excrement of animals.  That’s right, its fossil poop.  How this name came about is as fascinating as the material itself.

Up to the Civil war there was no established or organized system for collecting, cataloging, and storing a national collection of fossil (or any other national treasure).  After the Civil war the collecting of fossils, especially large fossils mushroomed.  The federal government started to access the natural wealth and resources of the expanding west.  This led to new discoveries of fossils at a mind-numbing rate.  Othniel Charles Marsh (O.C. Marsh (1831 – 1899)), a very wealthy banker educated at Yale.  J.D. Dana (father of modern mineralogy) influenced Marsh to do field collecting.  Marsh was educated, wealthy and was in the right place at the right time.  He lived near the Erie Canal as it was being dug and many fossils were exposed.  By the end of his life he had helped Yale amass one of the largest and most extensive fossil collections in the world.  It remains so today.

Edward Drinker Cope (E.D. Cope (1840 – 1897)) was a little younger.  At age 6, Cope started his scientific journal and by 10 was making his own observations and sketches.  By the time he was 17 he had become a member of the Philadelphia Academy of Science and 4 years later was a professor of Natural History at Haverford College.  Cope was not wealthy but he supported his family with income from renting his family farm out.

Cope and Marsh made many collecting trips to the west as well as working closer to home.  On at least one trip they went together collecting in the west.  When the railroad opened up access to the west both Cope and Marsh raced to the fossil fields to collect specimens and make reports.  Cope collected fossils with the famous Hayden survey while Marsh was affiliated with the King expedition. 
The competitive spirit of the two men led to an all out war within the scientific community.  Each man raced to produce the most professional papers and make the best discoveries.  Marsh let subordinates do the field work while he concentrated on lab work.  Cope saw the importance of seeing the fossils in their environment and did much of his own field collecting and observations.

In the end Marsh described 450 new species and a mountain of documents most which he donated to the U.S. National Museum (now called the Smithsonian).

Cope was more of an intellectual than Marsh.  Cope set the tone for vertebrate paleontology and the standard still measured by today.  Much of his work stood as the cornerstone in this field until the 1950’s.
During the fervent rivalry, a jealous Marsh named fossil excrement in Copes honor giving us coprolite.
There is an area of southern Utah where the canyons and valleys are so prolific with the coprolite that it used to be mined with a front end loader and hauled by dump truck to rock shops around the country. 
The best specimen-grade coprolite is the material that exhibits the entire “poop” shape which often resembles a cow pie.  When it comes to lapidary-grade coprolite the structure of the pattern on the inside is what is important.  The best patterns often resembles lightening bolts of

red in lighter colors.  Other desirable and rarer colors are the greens and lavenders and pastel purples.  The pattern on the inside is similar to septarian nodules which lends credence to the theory that septarians formed from decaying matter on the inside in a way similar to coprolite.

Much of this material has a softer exterior than the center.  Therefore the interior will tumble better that the rest. 
Not all coprolites are suited for lapidary work.  Coprolite is plagued with fractures.  Solid pieces without fractures are hard to come by and often the fractures are hidden until lapidary work is started.
There are coprolites that are not petrified with agate.  Some of the coprolites from St. George are replaced with limonite (natural rust) and will not polish.  These coprolites are not from large animals but are most likely from smaller reptiles and are much more recent than the dinosaur age.

There are coprolites as large as small cars, but when it is this large it is generally not good lapidary material.  The best material is much smaller.  Pieces to 25 pounds make for good lapidary rock.  At one time large spheres and eggs were popular fashioned out of this material.  Today it is mostly made into cabochons and display pieces.

By far the majority of the gem grade coprolite is found within the Morrison Formation of the Colorado Plateau, in the same areas as the gem dinosaur bone.
Some have been found to contain other recognizable fossils of things like broken teeth, gastroliths, seeds, bone, and wood.

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