Using Zircon to Date the Earth

Author: Stephen Caesar
Subject: Radiometric Dating
Date: 1/14/2005

One dating method that has led scientists to believe that the Earth is extremely ancient is to measure the decay of uranium trapped in the mineral zircon. Geologist Edmond Mathez, Curator in the Department of Earth and Planetary Sciences at the American Museum of Natural History in New York City and one of the discoverers of the undersea springs mentioned in Job 38:16, describes this method, as well as the problems with it. He writes that zircon

“can accommodate atoms of certain radioactive elements into its crystalline structure, and those elements can act as long-running clocks from which the age of the zircon can be read. The most important of those elements is uranium, which readily substitutes for zirconium in the crystal structure because the ions of both elements have the same charge (+4) and roughly the same size. The radioactive uranium locked up in the zircon decays to lead at a fixed rate. By measuring the relative abundance of those two elements in the zircon today, one can determine how long ago it formed.”

Perhaps unsurprisingly, the reality of dating a zircon is less simple than the foregoing explanation might suggest. One complication is that when zircon is heated during burial, some of the lead that had accumulated from radioactive decay can diffuse out of the crystal. The loss of that lead changes the ratio of lead to uranium, and so the new ratio, if measured, would give a spurious age (2004: 43).

Referring to attempts to date the Earth’s core via this method, Mathez reported:

“A second complication for dating zircon is that analyzing isotope ratios only in a zircon overgrowth or only in a core is not so easy. The reason is that those features are usually just a few ten-thousandths of an inch across, and the layers of overgrowth are not always visible in cross section, even under a high-power microscope. Yet to get an accurate picture of the history of a zircon, distinguishing one region from another is critical. Analyzing a zircon made up partly of material from the [allegedly] 3.5-billion-year-old core and partly from the billion-year-old overgrowth would give a meaningless age (Ibid.).”

Discover magazine reported on the consequences of the unreliability of zircon dating:

“Many geologists used to believe that Earth was a roiling mass of molten rock for the first 300 million years of its existence. But the zircon found by Simon Wilde, a geologist at the Curtin University of Technology in Perth [Western Australia], was formed just 160 million years after Earth itself. If the crystal could form so early in Earth’s history, the planet’s surface must have cooled and hardened considerably faster than researchers had suspected….[Evidence suggests that] the zircon formed within rock that had interacted with water on Earth’s surface. And that would mean the oceans formed earlier than had ever been suspected—more than 4 billion years ago (Rist 2002: 52).”

When you wade through the technical terminology and old-Earth bias, you see that dating the Earth, or any of its geological features, via the zircon method yields unsatisfactory results. Things are either younger than expected, or older. Thus, one more tried-and-true method of determining the extreme antiquity of the Earth proves to be unreliable.


Mathez, E.A. 2004. “A Birthstone for Earth.” Natural History 113, no. 4.

Rist, C. 2002. “Priceless Zircon.” Discover 23, no. 1.

Stephen Caesar holds his master’s degree in anthropology/archaeology from Harvard. He is a staff member at Associates for Biblical Research and the author of the e-book The Bible Encounters Modern Science, available at

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