Discussions

╳Discussions

Groups

Recent Images in Discussions

Mineralogical ClassificationLonsdaleite "discreditation"

24th Nov 2014 10:34 UTCMarco E. Ciriotti Manager

Here is a paper which substantially shows the non validity of the species: http://www.nature.com/ncomms/2014/141120/ncomms6447/full/ncomms6447.html

The discreditation is not - at today - formally approved by IMA CNMNC.

24th Nov 2014 11:02 UTCAlfredo Petrov Manager

Now if someone would please do this for chaoite too ;-)

24th Nov 2014 17:19 UTCUwe Kolitsch Manager

Page updated.

24th Nov 2014 18:01 UTCRob Woodside 🌟 Manager

This nicely side steps the issue of a polytype being a species.

24th Nov 2014 22:10 UTCJolyon Ralph Founder

So presumably at some point we should list it as a variety of diamond?

25th Nov 2014 09:34 UTCPeter Nemeth

It is not a polytype, the structure is not repetitive.

25th Nov 2014 17:56 UTCJohn A. Jaszczak Expert

The paper seems to have only studied Diablo "lonsdaleite" and diamond, but not the pseudomorphs after graphite from other meteorite impacts

like Popigai. Despite the title, it seems the authors are still suggesting more careful studies need to be done. They also don't seem

to have cited a fairly recent paper by Shumilova, et al. (2011) Natural monocrystalline lonsdaleite. Doklady Earth Sciences441.1(November 2011): 1552-1554. Unfortunately I cannot read the paper in Nature Communications till I get it from our Interlibrary Loan, and they may

be closed for the holiday.

25th Nov 2014 22:36 UTCStuart Mills Manager

It's not a discreditation as it does not investigate original material.

26th Nov 2014 17:15 UTCJohn A. Jaszczak Expert

Stuart,

The paper does note that they studied "natural samples from the Canyon Diablo meteorite, the type specimen from which 'lonsdaleite' was first described..."

The paper is really quite nice. I never realized that the extra diffraction peaks assocaited with lonsdaleite were

"very broad and poorly resolved", and were on the "shoulders of diamond peaks... or match those of graphite." I hope

they also study graphite pseudos from impact craters next for comparison.

It is also fascinating that two new twin laws are identified for diamond, on {113} and {110}.