Scientists, Philosopher Come Up With New Means of Categorizing Minerals

Scientists collaborated with a philosophy professor to propose a new "evolutionary system" of classifying minerals - one that reflects its rich history and the Earth's diversity.

The diamond, known in popular culture as a "girl's best friend" and the top of the Mohs' hardness scale, has become a general term regardless of these minerals' origin - designated by the International Mineralogical Association, Commission on New Minerals, Nomenclature and Classification. This includes diamonds formed billions of years ago, following the cooling of carbon-rich atmospheres of dying stars. The term also includes diamonds as we know them - gems formed through extreme temperatures and pressures deep in the Earth.

Working Around the "Diamond" Inconsistency

While the use of the term for a wide variety of chemically similar minerals does not seem to be a problem for physical scientists, the same can't be said for planetary scientists, paleontologists, biologists, and experts in other fields of study who place significance over the historical context that surround these minerals.

This led Robert Hazen and Shaunna Morrison, scientists from the Carnegie Institution for Science, to collaborate with Carol Cleland, philosophy of science professor from the University of Colorado Boulder, to develop a new system of classifying minerals. The results of their work are reported in the Proceedings of the National Academy of Sciences.

"We came together from the very different fields of philosophy and planetary science to see if there was a rigorous way to bring the dimension of time into discussions about the solid materials that compose Earth," Hazen explained in a press release from Carnegie.

The currently-used IMA classification system traced its origins to the 19th century when geologist James Dwight Dana proposed a classification system based on unique combinations of major element compositions, together with geometrically idealized crystal structures. Morrison cites quartz as an example of the IMA's outdated classification, which defines the mineral as pure silicon dioxide. She calls the experience of this definition "completely fictional," noting the presence of imperfections in actual quartz samples that provide insight as to how it was formed.

Parallel to Darwin's 'Theory of Evolution'

Cleland notes that "the IMA system is typical," sharing that similar categorization schemes are time-independent and depend "solely based on manifest similarities and differences, regardless of how they were produced or what modifications they have undergone."

While it is acceptable for other fields of study, a time-independent system does not work as well for historical-oriented fields of study, such as geosciences that emphasize the formation and development of bodies over extended periods of time.

Researchers noted a similar conflict in biology before Charles Darwin proposed his famous theory of evolution. This included discussions on whether bats can be classified as birds before mankind understands evolution, establishing historical relationships between different organisms. It led to a separate classification for both species, largely because of the absence of a common winged ancestor.

Since a universally-accepted "theory of evolution" exists for minerals, creating a new classification system is not as straightforward. The researchers then turned for a "bootstrap" approach, using these samples' chemical, physical, and biological attributes. Hazen argued that minerals are among the most durable and information-rich objects used in understanding the Earth's origin and evolution.

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