
4.4 billion-year-old crystal is oldest confirmed piece of Earth - pree
http://www.cnn.com/2014/02/24/world/oldest-earth-fragment/
======
yeukhon
I just search a bit about Jack Hills.
[http://en.wikipedia.org/wiki/Jack_Hills](http://en.wikipedia.org/wiki/Jack_Hills)
The last modified was last December. The actual paper
[http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo20...](http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2075.html)
was received last July but published on Fed 23, 2014. So it took a while to
confirm and accept by the reviewers using the new technique.

And Jack Hills seems to have caught a lot of attention as early as 2006.
[http://earthobservatory.nasa.gov/Features/Zircon/](http://earthobservatory.nasa.gov/Features/Zircon/)
and in this article, 4.4B crystal was mentioned. So the actual paper we are
reading today is really about using the new technique to confirm the age of
the crystal.

 _" Among the first important discoveries, says Watson, came out in 2001."_

Just think about an art from 10, 50, 100, 1000, 5000 and 10,000 years ago.
Then think about this 4.4B years ago. It isn't mind-blown; it's scary to think
about time. It takes millions of years for rocks to crush into each other and
make a planet. What is it like to see things from 4.4B ago? Then think about
the galaxy out there. People, the universe is an awesome and scary place.

Here is another article with an image explaining the idea of 4.4B with a
personal phone interview from the primary investigator.

[http://www.smh.com.au/technology/sci-tech/gem-found-on-
austr...](http://www.smh.com.au/technology/sci-tech/gem-found-on-australian-
sheep-ranch-is-the-oldest-known-piece-of-earth-scientists-
find-20140224-hvdkd.html)

~~~
teddyh
The almost incomprehensible age of the Earth was famously summarized thus:

“The reſult, therefore, of our preſent enquiry is, that we find no veſtige of
a beginning,–no proſpect of an end.”

— _Theory of the Earth_ , James Hutton, 1788

~~~
evincarofautumn
On a ſide note, we ſhould bring back the long S.

~~~
teddyh
Yea, and alſo þe þorn! More seriously; it’s a text from 1788 – I’d think I was
allowed to keep its spelling and not translate or transliterate when I’m
actually _quoting_ it verbatim.

~~~
evincarofautumn
It’s fine, I understood what you were up to. In earnest, though, I’d rather
see thorn and eth come back than long S.

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Shivetya
Dumb question, would finding this just be pot luck, or did they have an idea
of what they were looking at before they decided to subject it to the battery
of tests?

~~~
VLM
Zircons are industrially useful as the primary ore for zirconium metal. If you
keep it reasonably cool, like under red hot, it makes a great nuclear fuel rod
protective cladding, assuming you refine out the hafnium which does little
good in a fuel rod. Its also good for high temp ceramics, although too
expensive for your fireplace, probably. If you get the metal red hot and dip
it in water it does a fair impersonation of sodium being dumped in water at
room temp. Unfortunately, recently, an extremely large demonstration of this
effect was performed in Japan with predictable outcome.

Anyway there's lots of profit involved, leading to lots of geological
research, leading to interesting discoveries.

~~~
jofer
Actually, there's a lot of research on zircons because they're useful for
other research.

There are cases ("heavy mineral sands") where zircon is used as an ore, but
essentially none of the research on zircons has anything to do with this.

Zircons have a number of nice properties:

1) They contain trace amounts of uranium and (initially) no trace amounts of
lead. This allows them to be dated through U/Pb dating, which is relatively
precise and is still accurate over _very_ long timescales.

2) They can undergo heating to very high temperatures without allowing lead to
escape from the crystal lattice, resulting in the date being "reset". This
allows dating of the original zircon grain even after the rock hosting it has
gone metamorphism.

3) They're very durable physically and chemically. For this reason, they show
up in sedimentary rocks and preserve a record of what was being eroded to
produce the sedimentary rocks in question. Even when the sedimentary rocks
have been changed into metamorphic rocks, the zircons are often preserved.

4) They're not very rare. Zircon isn't "main" rock forming mineral, but it's a
not-too-uncommon accessory mineral in many igneous rocks (mostly in felsic
magmas). Because zircons are so durable, they show up in sedimentary and
metamorphic rocks sourced from the original igneous rock.

All of these reasons is why you'll see a lot of dating of zircons. They're
somewhat common, durable, easy to date, and yield accurate results.

This leads to a lot of uses that you might not think of at first.

For example, if you want to know where (geographically) a given sedimentary
rock was sourced from (i.e. what was eroded to form it), the most accurate way
is to use the "age spectra" of the zircons within it. You basically
disaggregate the rock, sort out the zircons (they're very dense), and date
every single grain of zircon (and sometimes many zones on every grain). You
take the distribution of ages that you get and compare it to the know ages of
large igneous bodies that were likely to be exposed and eroding at the time.
By matching the distributions (i.e. mixing models, etc), you can get an
estimate of where sediment was being sourced from.

This may sound esoteric, but it's very useful for things like oil exploration.

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mathattack
Isn't everything on the earth this old? The dirt in our backyard has been
around for 4.4 billion years too. Or is it that this crystal hasn't been
changed in that long?

~~~
s0rce
It solidified from the melt 4.4 billion years ago and hasn't remelted since.

~~~
Sharlin
Or otherwise changed. Metamorphism doesn't involve melting.

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jcutrell
In reference to the comments on this article, it really is quite a sad day
when creationism is reduced to the single "6500 years" theory by those who beg
for people to have a more comprehensive approach to the subject (Read: those
on the "side of science".)

It's somewhat of a double-standard critique.

Can we all agree that there are a massive number of views on this, and the
range between the views is quite a bit closer to continuous than absolute?

For instance, there are those of us creationists who believe in the story of
creation as somewhat allegorical, a cultural way of explaining a complex
series of events that originated from an intelligent design, possibly
including a singularity, evolution, and whatever else might be considered the
"anti-creationist" view.

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Aardwolf
Isn't everything on Earth as old? It's all the same material that was there
when the Earth formed, except for a few meteoroids that dropped on it later
during its lifetime.

~~~
bcbrown
The same atoms, but in different combinations and configurations. What's
newsworthy here is that this chunk of atoms has been in the same configuration
for 4.4 billion years, and that the configuration can tell us something about
the history of earth.

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aurora72
According to BBS Earth Biography series, half of all the water in the world
came from a comet colliding to earth some 4 billion years ago.

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anxrn
The article does not seem to touch upon the possibility that the crystal was
of extra-terrestrial origin.

~~~
chc
At that time, I think the distinction is a little more fuzzy. The entire
planet was of extraterrestrial origin.

