National Geographic

Letting Gems Speak: My New “Matter” Column For The New York Times

We typically look at rubies and other gems as treasure, bling, or signs of matrimony. But they are also historians, telling us about what the Earth was like hundreds of millions of years ago. In today’s Matter column in the New York Times, I talk to geologists who treat jewels as archives of planetary history. Check it out.

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  1. J. W.
    June 13, 2013

    In an otherwise fine article, I was very shocked to read the last few paragraphs:

    “The oldest deposits of jade and rubies date to only about 600 million years ago. The Earth itself is more than 4.5 billion years old, which naturally raises the question of why there aren’t any jade stones or rubies from the first nearly four billion years of the planet’s existence.

    Dr. Stern, for one, thinks the answer is that plate tectonics — the stirring of the planet’s interior that drives plates around its surface — didn’t exist for most of Earth’s history. “I would say it started less than a billion years ago,” he said.

    That’s a controversial idea in the geological community. Perhaps gems may someday resolve it.”

    There is abundant evidence from cross-continental sequence stratigraphy, paleobiology, and, most importantly, paleomagnetism, that plate tectonics has been operating for billions of years. I don’t know how else you explain the movement of plates (that we can clearly observe!) in the absence of plate tectonics.

    The simplest, and most likely, explanation for the lack of Proterozoic and Archean jade deposits is precisely the action of plate tectonics. With enough recycling of oceanic and continental crust, it is highly unlikely that soft minerals such as jadeite would survive to the present. We also don’t have that much Proterozoic and Archean age rocks to begin with.

    I’m disappointed to read such an out of the mainstream view presented uncritically, and I am not looking forward to having to explain to my undergraduate students (who read the NYT Science coverage faithfully) why this is wrong.

    [CZ: Dear J.W.: Your students could just as easily read about Dr. Stern's claim in the paper in Geology that originally inspired my column. If the editors of one of geology's leading journals felt that it was an idea worthy of publishing in their pages, I hardly see why you should single me out.]

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