Re: Old zircons

erik simpson wrote:

Ancient crystals suggest early Earth had land and freshwater

"The zircons represent a rare report from the mysterious Hadean, the geological time period that ended about 4 billion years ago, 500 million years after Earth’s formation. The planet, originally a ball of magma, had cooled off and formed a crust. Somehow, perhaps from a bombardment of water-rich asteroids, it had accumulated a global ocean. Earth may have remained watery for quite some time—at least until tectonic processes began to recycle Earth’s crust into its interior, and magma bubbled up in chains of island volcanoes that eventually fused into continents.

Much of this is guesswork, because almost no rock survives from the Hadean. The oldest rock with a reliable age—a gneiss from Canada—is 4.03 billion years old. The only surviving material from before then are zircons, found embedded in younger rock, which are as much as 4.4 billion years old. “Just about any information that we can get from these Hadean zircons is useful because it’s our singular record of the Earth’s first 500 million years,” says geologist Stephen Mojzsis of the HUN-REN Research Centre for Astronomy and Earth Sciences."

https://www.science.org/content/article/ancient-crystals-suggest-early-earth-had-land-and-freshwater

very interesting, thanks! The only thing I know about zircon is
something about its etymology - a rare example of a doublette.
"Jagoon" in English is both a type of zircon, and also a term for
fake jewelry sold as genuine. It came to English via French "jargon",
which got it from Italian giargone, which got it from Persian
"zarqūn". The same Persian word was used by the German mineralogist
Abraham Gottlob Werner to create "Zirkon" and "Zirkonium", which then
also made its way into English (and lots of other languages).
Weber was the father of German geology (and honorary fellow
of the Royal Society of Edinburgh...)and had developed an early theory about the stratification of the Earth's crust - also a promotor of the now
obsolete Neptunian theory. To link this with another thread, he was
also a sort of Linnaeus for mineralogy and developed a comprehensive
system  how to identify and classify them. As a side result, he also developed his own color nomenclature, that matched colors with specimen
from  flora, fauna and minerals. It was massively influential also among
artists, especially when in 1814, the Scottish painter Patrick Syme
published an amended translation as "Werner's Nomenclature of Colours"
in Edinburgh. A certain Charles Darwin read it as a student here, who was deeply impressed and used it later extensively in his notes and reports.