Geologic Taxonomy

I was just reading Stephen Jay Gould's new book "Leonardo's Mountain of Clams and the Diet of Worms : Essays on Natural History", the latest collection of his essays from Nature. He had a tragicomic tale in there about a fellow whose major lifes work was an attempt to develop a description of rocks, soils and stones based on the same taxonomic structure that Linnaeus developed for biological species.

Linneaus was remarkably successful in his classification scheme because ultimately species ARE related to each other -- evolution works in a branching, tree-like manner, and forms are derived from other forms. However, the same scheme, when applied to rocks, fails miserably. Gould discussed this fellow's 11 "Species" of granite, and his numerous distinctions of "clays" and how he could rarely tell one from another.

The reason for this was that the taxonomic scheme had no grounding in the reality of the way that rocks are formed. It was a herculean intellectual exercise, but it did NOT add to the sum total of human knowledge because it did not help understand anything, nor form the basis for predictions about the properties of related rocks. Only historians of science remember this effort, and it is not part of the working knowledge of a geologist.

So today instead of discussing the Family, Genus and Species of a rock we say it's either Igneous, Sedimentary or Metamorphic. This is based on something intrinsic about the rock itself, and lends itself to prediction of its properties.

KyleBrown