[Rockhounds] Diamond clues to beasts' demise

[pmodreski at aol.com]

A P.S. to the 13,000 b.p. impact-produced diamonds discussion,

After reading all these posts (or at least most of them) about this 
topic, I found I was able to go through our USGS library online and 
read the original article in the journal, Science, about it (2 Jan 
2009, vol. 323; "Nanodiamonds in the Younger Dryas Boundary Sediment 
Layer" and, even better, the "News of the Week-Planetary Impacts" story 
 from that issue of Science, "Did the Mammoth Slayer Leave a Diamond 
Calling Card", which described the background for this research (and 
which is much more readable).

It seems that our Rockhounds discussion got onto somewhat of a side 
track about whether "hexagonal diamonds are still diamonds".  Nice 
discussion, but, though the BBC story did use these terms, unless I am 
missing it, the actual Science article by D.J. Kennett et al. never 
mentions lonsdaleite, nor anything about "hexagonal".  It refers to 
them as "nanodiamonds", also as "the n-diamond polymorph", which 
crystallizes "under lower temperature-pressure conditions".  They also 
refer to recovery of "typical cubic diamonds" from one site (Bull 
Creek, Oklahoma), and describe "subrounded, spherical, and octahedral 
crystallites, ranging in size from 2 to 300 nm, distributed within 
carbon spherules", and refer to electron diffraction patterns producing 
"d-spacings typical of cubic diamonds" as well as "additional 
'forbidden' reflections consistent with the n-diamond polymorph".
0D
The News of the Week" story notes that other researchers have still 
questioned the interpretation of this data, and some groups have 
reported carbon spherules and nanodiamonds from other soil horizons of 
various ages, questioning whether there is really any correlation with 
an impact event or events.  [maybe they are just generic cosmic dust 
filtering down to Earth??--my comment, not theirs]

and, a P.P.S. to this, I see that it's not 13,000 years BCE or B.C. as 
some have been quoting but (the authors actually said 12,900) years 
B.P., = "before present", which means approx. 11,000 B.C.

There is another very interesting article just published, about 
apparent evidence for a tsumani, inferred to have been caused by an 
impact, 2300 years ago (=300 B.C.) in the New York City - Long Island 
area.  See geology.com, which linked to a story in National Geographic 
News:

http://news.nationalgeographic.com/news/2008/12/081231-new-york-tsunami.html

have fun,
Pete


-----Original Message-----
From: DonH <donhalterman at verizon.net>
To: erich kern <efkern at earthlink.net>; Rockhounds at drizzle.com: A 
mailing list for rock and gem collectors <rockhounds at lists.drizzle.com>
Sent: Sat, 3 Jan 2009 5:56 pm
Subject: Re: [Rockhounds] Diamond clues to beasts' demise


erich kern wrote: 
 
> !3,000 yrs BCE 
> > > 
http://newsvote.bbc.co.uk/mpapps/pagetools/print/news.bbc.co.uk/1/hi/sci/tech/7808171.stm?ad=1 
 
OK, now we have some clarity on w
hat's being said: 
 
"...lonsdalite, or hexagonal diamonds, associated with meteorite 
explosions." 
 
So this is some bad terminology. Pretty sad. 
 
Don