Pearls Buried in Soil as a Quality Test

Recently a reference librarian at University of North Carolina-Chapel Hill's Walter Royal Davis Library made an inquiry on behalf of a patron.  The patron recalled reading "a tidbit about pearls" but was unable to place the source.  Specifically, the information they were trying to verify was that "chemists" or others in the Middle Ages would bury pearls in the dirt or soil to somehow test the quality of the pearls, and had we ever heard of this activity?

Eve's response: "I do believe the fact of the assertion is correct, the stated purpose is incorrect.  To explain: Pearls are made up of calcium carbonate, and are soluble in acids. Quite often a (natural) pearl would be found, of a certain size, but perhaps with a cloudy or blemished surface. Because pearl nacre is laid in layers by the mollusks, if a top layer could somehow be removed, there would be some hope of finding a better, brighter, unblemished layer below, albeit of a smaller size pearl.

One method used until this century in Europe was to run the pearl "through a chicken": allowing the chicken to swallow the pearl, then anxiously watching for its re-emergence at the other end.  The stomach acids would have dissolved the outer layer, hopefully resulting in a prettier pearl.

To this day, there are, in the pearl world, a few individuals known as "Pearl Doctors", who have mastered the delicate skill of painstakingly peeling the outermost nacre layer from important pearls.  They can command hefty fees, and possess the ability and experience of deciding whether a given pearl is likely to be improved or not. The Pearl Society owns some pearls from the collection of the late, and renowned pearl specialist, Lowell Jones, who collected $5000 dollars a day, payable in dollars or Swiss Francs, plus expenses and travel on the Concorde, and that was in the 1970's!    

It is thus more than likely that the individuals who sought to bury pearls in soil in the Middle Ages were in fact hoping that acidity would eat away the surface of the pearl and cause an improvement. It may well be that, being unable to test the pH of the local soil, they were reduced to experiment. Hence the vague idea that "they were testing the quality of the pearl", when actually it was the quality of the soil that was in question. 

I hope that is of help.  You probably found us through the website  www.evejewelry.com , which leads to our Pearl Blog, www.pearlsociety.typepad.com . If you would like to subscribe to the Pearl Society printed newsletter, which appears 4 times a year (sometimes 5) and carries separate material, please let us know.
Subscription, which includes membership in The Pearl Society, is $25.- a year.

-Eve Alfille
Founder, The Pearl Society

Comments

[Caitlin Williams]

I have always thought that running a pearl through a chicken is an urban legend and this is why:

Chickens have crops and gizzards instead of a stomach. They pick up bits of oyster shell and little rocks which reside in the crop and grind everything else the chicken eats to a mealy consisency before it passes through the chicken. The little rocks and pieces of grit, do not pass through the chicken, but stay in the crop, so how could a pearl of any size pass through a chicken?

I would appreciate it if you can actally subtantiate this method of pearl pealing as I find it impossible unless you kill the chicken to take the pearl out of the crop before it is ground to powder.