A Question

My sister in law is an artist and is writing a proposal for funding a project. She intends to use red clay to make some figurines. She has heard an old story that the composition of red clay is similar to the composition of the human body and is wondering how much off the mark is that statement. I am pretty sure that at the level of molecules/compounds the difference is huge, but I am not sure how big is the difference if one breaks down the chemical composition down to elements/atoms. I suspect that carbon and hydrogen may be close, but how about nitrogen, oxygen or, even more difficult for me to find out: copper, phosphorus, iron, sulphur, manganese, etc.? Do you know?

2 responses to “A Question

  1. I don’t know much about human body composition (other than there’s a lot of water) but I doubt there’s a close relationship between clays and living organisms. The chemical formula for the most complex family of clays, montmorillonite, is

    X0.2-0.4 Y2 Z4 O10 (OH)2 * nH2O

    where
    X is some combination of calcium and sodium,
    Y is some combination of aluminum, magnesium, and iron, and,
    z is some combination of silicon and aluminum.

    Other clay chemistries are basically reductions of this. Red clay would undoubtedly have a fair amount of iron in the Y position. But no carbon, lots of silicon and aluminum, and enough iron for a red color (which actually doesn’t take a whole lot). *

    If this is similar in composition to the human body, I’d be very surprised. Just as a guess, I’d say the story came about because the red color reminded somebody of blood.

    * source: Perkins, D., 2002, Mineralogy, 2nd ed., Prentice Hall, Inc., p 313.

  2. The information on Wikipedia seems to indicate the same: That there isn’t very much similarity.
    See:
    http://en.wikipedia.org/wiki/Clay
    and the various links listed therein.