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Identity HelpMineralogical studies
10th Jan 2010 21:01 UTCTrish Wilson
http://openlibrary.org/b/OL19931909M/Mineralogical_studies_of_archaic_jades
http://www.earth.sinica.edu.tw/webearth-library-en/journals/wpes/Vol2/No3/V2n3p239.pdf
http://www.ijvs.com/volume3/edition4/section1.html
Feature Article in the above link:
2. Non-destructive identification of minerals
by Raman microscopy
Ray Frost, Theo Kloprogge, and Jolene Schmidt
Centre for Instrumental and Developmental Chemistry,
Queensland University of Technology,
Brisbane, Queensland,
Australia
Introduction
The identification of minerals is, in many cases, based on techniques like X-ray diffraction, optical microscopy and electron microprobe analysis. A major disadvantage of these techniques is that the mineral crystals have to be destroyed either to a powder or a thin section. Raman spectroscopy has been used for the identification of minerals <1-5>. This paper describes the application of Raman microscopy <6> as a non-destructive technique for the identification of minerals, suitable also for single crystals as small as a few hundred micrometers <7>.
The identification of minerals generally starts in the field by visual examination by a geologist. Based on properties such as colour, crystal habitus, hardness, lustre, cleavage, etc. often in combination with detailed knowledge of the regional geological history a first identification of many rock-forming minerals is possible. It becomes more difficult for the more rare minerals mostly present in only minor amounts and often as small crystals. In many of these cases visual examination even by an experienced mineralogist does not give a definite answer and other analytical techniques are needed in order to come to an identification of a mineral. The classical petrologist or mineralogist will start with the preparation of thin sections of approximately 30 microns thickness of the rocks sampled in the field for examination under the optical microscope. Optical properties such as colour, pleochroism, refractive index, birefringes, etc. allows minerals to be identified. However, this method is rather timeconsuming and depends strongly on the experience of the geologist. Alternatively, minerals can be identified by their crystal structure by X-ray diffraction and chemical composition by methods like electron microprobe analysis. In general, X-ray diffraction uses powdered samples, whereas the electron microprobe uses thin sections similar to those for optical microscopy, but without coverglass and coated with carbon. This can pose a problem for the identification of very small or rare crystals. An interesting non-destructive alternative is a spectroscopic technique generally known as Raman microscopy. In this paper we report a number of spectra of various minerals, all with crystals not larger than a few millimetres. This will show the strength of the Raman microscopy technique as it will show that each spectrum is unique and can be used as a sort of fingerprint for the identification of the mineral when a large enough database of mineral spectra is available.
Raman microprobe spectroscopy
The Raman effect is a light scattering effect (see for example The Spectroscopists Bookshelf: http://www.ijvs.com/bookshelf.html). In order to obtain the Raman spectra of minerals, minerals were placed on a polished stainless steel surface on the stage of an Olympus BHSM microscope, equipped with 5x, 20x and 50x objective lenses. No sample preparation was needed. The microscope is part of a Renishaw 1000 Raman microscope system, which also includes a monochromator, a filter system and a charge coupled device (CCD). Raman spectra were excited by a Spectra-Physics model 127 HeNe laser (633 nm), recorded at a resolution of 2 cm-1 in sections of 1000 cm-1 for 633 nm excitation. Repeated acquisitions using the highest magnification, were accumulated to improve the signal to noise ratio in the spectra. For the 298 K spectra, data were collected at 20-second intervals for 10 minutes at maximum magnification. Spectra were calibrated using the 520.5 cm-1 line of a silicon wafer. It should also be noted that the filters in the Renishaw spectrometer start to eliminate the Rayleigh line at about 150 cm-1. This makes the determination of bands below 200 cm-1 difficult and without reliability.
Spectra obtained with the microprobe normally consist of Raman bands superimposed on a background, which is a combination of the fluorescence and the instrument function. In the case of the HeNe laser and the measurement of the hydroxyl stretching region, the background is predominantly due to fluorescence and consists of a sloping linear baseline that is easily corrected. For the HeNe laser and the determination of the low frequency region, the background is predominantly a combination of the instrument function that is dependent on the behaviour of the notch filters, the grating-detector responses, and the fluorescent background. This background is induced by elements placed in the optical path between the sample and the entrance slit of the spectrometer. The background, although a complex function, is easily measured using the incandescent white light from the microscope. The measured spectra are then ratioed to this instrumental background to give the spectra as illustrated in the figures in this paper. Such a method ensures the correct instrumental function is taken into account and that the true spectrum is measured. Different instrumental profiles are obtained for the operation of different lasers.
Normally with conventional dispersive Raman spectroscopy and to lesser extent, Fourier transform Raman spectroscopy data collection times can be excessively long, particularly for minerals. Often for poorly scattering minerals such as clays, several thousand FT Raman spectra must be coadded to obtain a spectrum of sufficient quality. In the case of Raman microprobe spectroscopy with multiplex detection, data collection times are very short and spectra are easily obtained within 1 to 10 minutes. Typically a collection time of 60 seconds, in which 10 spectra are co-added, is used with the maximum magnification. Power at the sample is in the 0.1 to 1 mW range. This use of such low power is a major advantage particularly over that used for FT Raman spectroscopy where typically the power used for minerals is 100 mW for a spot size of 200 m. For Raman microscopy, the laser spot size is 0.8 microns and the laser power is between 1 and 4mW. Such low power means that there will be no heating effects and consequential damage to the mineral. It was found that the best quality spectra were obtained by scraping fresh crystals from a lump of the raw material on the metal support. Crystals of the kaolinite are easily observed under the microscope.
One of the disadvantages of Raman microprobe analysis is the fluorescence of the clay minerals which is particularly pronounced when using the HeNe laser at 633 nm and other lasers of similar wavelengths. Each of the laser lines used to excite the Raman spectra of the kaolinite polymorphs caused fluorescence that subsided with time. Even so difficulty of measuring the low frequency region with the 633 nm excitation was experienced and the use of the diode laser operating at 780 nm did not alleviate the problem. Obtaining spectra at 77K, meant that the instrumental background shifted with temperature. This shift may be related to the change in the fluorescence of the sample at liquid nitrogen temperatures. Unique spectra from kaolinite polymorph crystals were more difficult to obtain from ground or powdered samples. If the crystals are smaller than the resolution of the microscope then spectra are obtained from an area that covers several crystals and an averaged spectrum is obtained.
An advantage of Raman spectroscopy is that bands in the 200 to 400 cm-1 region are easily measured. Dispersive Raman spectroscopy inherently has the clay spectrum superimposed on the intense Rayleigh line. The use of Raman microscopy employing CCD detectors is greatly advantageous because of signal to noise improvement. Detectors in both FT Raman spectrometers and conventional dispersive instruments are photon noise limited. With a CCD detector this is no longer true: typically the noise from a CCD detector is at least 100 times less than from a semiconductor detector. The disadvantage of using Raman spectroscopy operating at the diode laser frequency of 780 nm is the loss of scattering efficiency. Raman scattering decreases as the fourth power of the wavelength of the scattered radiation, so the intensity of the Raman scattering at 780 nm compared to say 532 nm is ~7 times less. For the 633 nm (HeNe) laser, this factor is 2. Nevertheless, the disadvantage of this loss of efficiency is greatly outweighed by the advantages of the CCD detector. Further the advantage of using lasers operating in the 633 or 780 nm range rests with the reduction of the laser induced fluorescence which is a problem when using green or blue excitation wavelengths.
10th Jan 2010 23:25 UTCTrish Wilson
When this jade first came to our collection, we had no idea what the mineral inclusion was. What we could see was that it was raised slightly above the surface of the carving.
10th Jan 2010 23:31 UTCTrish Wilson
10th Jan 2010 23:53 UTCRob Woodside 🌟 Manager
11th Jan 2010 01:14 UTCAlex Homenuke 🌟 Expert
11th Jan 2010 02:08 UTCTrish Wilson
Please do a search for 'pyrite' and you will find the crystal shapes of this mineral.
Re the pyrite being raised above the surface of the jade, we have a number of examples of archaic jades which display this feature. We believe that in some cases, particularly the very ancient examples, i.e. the Neolithic carving I've shown on this thread, this could be caused because of the erosion of the jade.
The idea that the examples of pyrite shown on the closed thread are pyrite paste, is quite ridiculous.
11th Jan 2010 02:16 UTCTrish Wilson
11th Jan 2010 16:27 UTCAlex Homenuke 🌟 Expert
The reason this thread interests me is that in a past life I managed a jade mine and studied nephrite for a couple of years. I had never found a sulphide, let alone pyrite as an inclusion. My studies did not include ancient jades, though I do have a couple of pieces. I decided to try an internet search and wound up on EBay (item 350297676507). I had some doubt that the intense metasomatism would allow a sulphide to crystallize within a nephrite deposit - the attached picture has convinced me!
11th Jan 2010 17:04 UTCJolyon Ralph Founder
I'm at a loss as to what the question actually is here. This section is entitled "Identity Help", what is it you wish to have help with? I think you have all the answers already.
11th Jan 2010 18:08 UTCRock Currier Expert
11th Jan 2010 18:35 UTCRob Woodside 🌟 Manager
"Alex, the answer to your question is in my picture of the graph (Mindat - Neolithic pyrite b). The highest peak is tremolite, the next highest is actinolite. The two together constitute nephrite jade. The small peak is pyrite.
Have a look at these these Raman spectra:
Pyrite http://rruff.info/pyrite/display=default/R050070
Tremolite http://rruff.info/tremolite/display=default/R060311
Nephrite http://rruff.info/nephrite/display=default/X050001
Jadeite http://rruff.info/jadeite/display=default/R070117
Your spectrum is correct as labeled. It is a pyrite spectrum with nothing to do with tremolite or actinolite and has nothing to do with nephrite jade.
It would be interesting to see how deep these pyrites go into your carving. Since pyrite has a density nearly twice the other purported minerals a density measurement which is completely non destructive should tell the tale.
Pyrite is fairly easy to synthesize, so a real possibility is that they are a surface phenomenon and were grown there.
I agree with Rock about whether this is Nephrite jade.
12th Jan 2010 00:33 UTCEzekiel Hughes
New Zealand
Alex, I'm still not a believer but will keep an open mind. I have heard rumors of pyrite inclusions in jade from around our area and have found jade like junk with flakes of pyrite...i guess i should have it tested...but I doubt it is what it appears to be. Also, what exactly is "New Zealand Greenstone Pounamu Nephrite Maori Jade"
Actual ebay link:
Ebay New Zealand Jade Link
Also, how come there aren't specimens of pyrite crystals on natural nephrite stones buried in the earth? That is if the idea of them growing after the piece was buried is to be believed.
Also, in regards to secondary tremolite growth, wouldn't the proper P & T be required? I think there are plenty of questions to be answered.
When I read of associate pyrite in occuances of nephrite, it is in association along with a dozen other minerals and rocks...notice the location of the pyrite in the NZ piece...in the black...serpentinite often has pyrite right?
Ironically the color of the piece Trish is showing us here could be jade...it is a product of secondary weathering (oxidization in in the proper soil enviroment...aka vulcanization) either before carving or after or it isn't jade. Can't tell jade by color alone. However most "red jade" isn't jade.
12th Jan 2010 01:04 UTCTrish Wilson
Rock, nephrite jade comes in a wide range of colours. The small horned figure has likely been carved from multi-coloured jade that comes from Liaoning Province.
Picture attached shows two nephrite boulders from Liaoning, each weighing approximately 16 kgs.
12th Jan 2010 01:36 UTCTrish Wilson
I am hoping that someone here may see something from the pictures below to make a positive identification.
The first lot of pictures are of a mythical animal. We do believe the base material is nephrite. The inclusions run in a very distinctive band through the left side.
12th Jan 2010 01:47 UTCTrish Wilson
12th Jan 2010 01:51 UTCTrish Wilson
12th Jan 2010 01:58 UTCTrish Wilson
12th Jan 2010 02:05 UTCTrish Wilson
12th Jan 2010 03:21 UTCAlfredo Petrov Manager
12th Jan 2010 03:55 UTCEzekiel Hughes
12th Jan 2010 05:27 UTCTrish Wilson
Please look at the top of the picture showing the outside of the lid of the jar. The interwoven structure of nephrite crystals should be very obvious.
Show me an example in serpentine where you can see this.
12th Jan 2010 06:10 UTCCraig Mercer
12th Jan 2010 06:31 UTCEzekiel Hughes
12th Jan 2010 07:12 UTCTrish Wilson
You have totally missed the point here. The question was about the identity of the inclusions, not of the base material. We know exactly what that is.
Zeke, I really do not think you are in a position to judge the work done in ACTA Geologica Taiwanica.
Professor Hsien Ho Tsien is a member of the Faculty, Paleontology, Department of Geology, National Taiwan University, and was the guest editor of ACTA Geologica Taiwanica, Mineralogical Studies of Archaic Jades, 1996. The book is dedicated to Professor Li-Pin Tan in recognition of his work in pioneering studies of tremolite jade. Professor Tan graduated with honors from the Department of Geology, National Taiwan University in 1953.
About ACTA Geologica Taiwanica: “The Symposium on the Mineralogical Studies of Archaic Jades was organized jointly by the National Taiwan University and the Taiwan Museum, and was held on the campus of the University on January 12 and 13, 1996. The purpose of the Symposium was to discuss recent developments in mineralogical and geological studies of archaic jades, to exchange ideas and to establish scholarly contacts in this specialized field of research.
“During the Symposium eleven papers were presented in Chinese and English. Seven have been selected for this volume after final revision by their authors. Thus this volume represents the Proceedings of the SMSAJ.”
About the Department of Geology, National Taiwan University: “Active research on various geologic topics is the tradition of this Department. Major funding agencies include National Science Council, Central Geological Survey, Bureau of Environment Protection, Bureau of National Park Administration, Commission of Atomic Energy, etc. Research results appear in both domestic and foreign professional journals. The Department also issues one volume of high standard research report "Acta Geologica Taiwanica" annually, and cosponsors the Chinese journal "Ti-Chih" with the Geological Society of China and the Central Geological Survey.
“The Department has long been the major institution supplying the Republic of China with well trained geologists. Its alumni are engaged in various phases of geological work both in Taiwan and abroad. Because of the economic prosperity of the Republic of China in recent years, the increasing demand for geologists is expected.”
Professor Tsien used both documented and undocumented jades in his research project.
12th Jan 2010 07:55 UTCEzekiel Hughes
12th Jan 2010 08:38 UTCTrish Wilson
It is clear that you have nothing to add on the identification of the inclusions.
12th Jan 2010 08:59 UTCEzekiel Hughes
12th Jan 2010 09:13 UTCTrish Wilson
12th Jan 2010 09:40 UTCHarjo Neutkens Manager
Your last posting was not very polite, this is not the way to discuss here on Mindat.
Bottom line is, Trish, if you can't handle an open debate about a piece then don't.
12th Jan 2010 09:54 UTCJolyon Ralph Founder
Can the original poster please explain to me why I should keep this thread open, what are we debating here?
12th Jan 2010 10:10 UTCJolyon Ralph Founder
But because of the excellent state of preservation of the pyrite and the heavily weathered surface of the "jade", the only logical conclusion I can see that explains this is that it is a recent carving that has been treated with acid. Natural weathering would have likely caused more deterioriation to the pyrite.
Jolyon
12th Jan 2010 10:29 UTCTrish Wilson
I can work things out for myself and can see that there is nothing more to glean from the members. So you may certainly close the thread.
Your forum is infiltrated by Anita Mui through her good friend and assistant, Ezekiel Hughes, who was not content with addressing my questions within the legitimacy of this site. Read through some of his postings on her forum:
JadeJunkee
Post subject: Iron pyrite in nephrite?
PostPosted: Sat Jan 09, 2010 11:31 am
User avatar
Joined: Wed Nov 25, 2009 6:23 am
Posts: 36
Please review this thread on mindat and either jump in on that board or give me some of what you know with links to etc...
http://www.mindat.org/mesg-11-167252.html
~Zeke
JadeJunkee
Post subject: Re: Iron pyrite in nephrite?
PostPosted: Mon Jan 11, 2010 10:32 pm
User avatar
Joined: Wed Nov 25, 2009 6:23 am
Posts: 36
I'm trying to post links to two examples of real jade with pyrite inclusions....but seem to be failing....
I've heard of the stuff before and personally have some "semi-nephrite" with small flakes of pyrite...but i have trouble calling it jade as it is of such terrible quality...i call it an ugly garden rock.
JadeJunkee
Post subject: Re: Iron pyrite in nephrite?
PostPosted: Tue Jan 12, 2010 3:04 am
User avatar
Joined: Wed Nov 25, 2009 6:23 am
Posts: 36
I've decided to dial it up a notch and am calling in some renowned experts ;-) Trish has started a new post on Mindat....don't reply yet...let her bury herself for awhile....the moment you reply the mods will close the post because they don't want it to turn into a fight. let me get some undisputable, unbiased opinions from "untouchable" authorities....that last link was provided by Trish...one self referencing paper does not make a valid theory :-) I have no doubt myself...why do all her pieces have the exact same "weathering" patterns? why does the pyrite pop out? There is one close up she provided that gives me pause, but then reason takes over. where are all the rough jades with pyrite for sale? where are the examples not from her collection? .....why do i have to pay $50 to post on thier site if they really have all these archaic jades, shouldn't that be modivation enough to have an open site? Anita, your tenacity is impressive.
JadeJunkee
Post subject: Re: Iron pyrite in nephrite?
PostPosted: Tue Jan 12, 2010 3:44 am
User avatar
Joined: Wed Nov 25, 2009 6:23 am
Posts: 36
I sent the email out to someone i trust...might be a few days....don't get on the new thread...It'll only close it down.
12th Jan 2010 10:36 UTCBen Peters
I suppose Trish's initial question is simply a call for opinions on the nature of the inclusions - to which some have been stated. Any piece of rock with photos posted might be some kind of fake, so I see no reason to be prejudiced against a sample which happens to be presented as archaic jade.
I am also interested to know if anyone with nephrite jade experience knows of any potential mining or river sources for material like this within China, assuming it is nephrite with pyrite inclusions?
Anyway, please leave the thread open; I am in possession of some similar material, and I am having some Raman tests done tomorrow. I will post the results tomorrow/Thursday. This should at least confirm some premises.
Thanks,
Ben
12th Jan 2010 10:42 UTCJolyon Ralph Founder
>I am also interested to know if anyone with nephrite jade experience knows of any potential mining or river sources
>for material like this within China, assuming it is nephrite with pyrite inclusions?
Thank you, this is a far more reasonable question, and I'd hope someone would be able to help.
Jolyon
12th Jan 2010 10:43 UTCCraig Mercer
12th Jan 2010 10:44 UTCTrish Wilson
From our experience with Raman testing, the test for the mineral Nephrite is quick and simple. However, you may find they have more problems with the pyrite, if that is what it is.
12th Jan 2010 13:18 UTCBoris Erjavc
Good luck
Boris
12th Jan 2010 20:21 UTCRob Woodside 🌟 Manager
12th Jan 2010 22:43 UTCTrish Wilson
I'm afraid I know little about the tools needed for testing the bronze coloured inclusions other than through a lab. What is a magnitized needle?
As to the debate of whether the carvings are nephrite or serpentine, Ben is having some pieces tested today, including an item from the same batch as the animals, and it will be interesting to have the results.
I am attaching pictures of another Neolithic item. In this case it is carved from a serpentine form, antigorite. We have had this stone tested through QUT; Dr. Cook has also had some tested through the Calgary University. From the pictures you will see that the surface shows a secondary mineral, which has not been identified. The secondary is hard, shows no particular habit, has a metallic sheen in some areas, either black or bronzed. The bronzing shows only in tiny specks on the dark brown to black. The secondary mineral is slightly raised above the surface. The stone itself is silky smooth, where nephrite is fibrous in the weathered areas.
We have tried to get secondary minerals tested through Raman, but it is a very slow process and the price is prohibitive.
This piece is 27 x 20 cm.
12th Jan 2010 22:49 UTCTrish Wilson
12th Jan 2010 22:54 UTCCraig Mercer
12th Jan 2010 22:55 UTCTrish Wilson
Thanks.
12th Jan 2010 23:03 UTCEzekiel Hughes
12th Jan 2010 23:47 UTCRob Woodside 🌟 Manager
To magnetise a needle rub it against a magnet. When magnetised and suspended by a thread attached to the centre of the needle, it will point north.
13th Jan 2010 01:47 UTCTrish Wilson
Also, will try the magnetized needle test on the others.
Thank you, again.
13th Jan 2010 02:44 UTCAlex Homenuke 🌟 Expert
The first specimen with the pyrite cubes - to me these are phenocrysts which likely formed by a diagenetic process, not the metasomatism that forms nephrite.
The river boulders definitely look like nephrite and the weathering is what I would expect to see. Most of the artifact pictures don't look like this.
I agree with others comments that the level of weathering suggested by the pictures should affect the pyrite more.
I took another look at the EBay nephrite/pyrite from New Zealand - this looks like later emplacement on a fracture - there is alteration along the fracture supporting this observation.
The mention of weathering showing the felted texture of nephrite - an SEM (scanning electron microscope) is required to see texture in nephrite. If coarse enough to see on surface it could still be the tremolite/actinolite composition.
Other inclusions common in nephrite are chromite (steely gray polished) and ilmenite - this could be the resistant brownish patches on the antigorite carving.
I still have not found a reference positively identifying pyrite as an inclusion in true nephrite.
Disclaimer - my opinions only based on pictures
13th Jan 2010 04:40 UTCEzekiel Hughes
http://i790.photobucket.com/albums/yy184/jadadara/SerpPyrite/SerpentinewithPyrite001-Copy.jpg
http://i790.photobucket.com/albums/yy184/jadadara/SerpPyrite/SerpentinewithPyrite002-Copy.jpg
http://i790.photobucket.com/albums/yy184/jadadara/SerpPyrite/SerpentinewithPyrite003-Copy.jpg
When I asked if the serpentinite undercut compared to the pyrite while polishing so that the pyrite stood out he siad yes. He indicated the serpentinite around the pyrite had a hardness around 2 whereas the bulk was harder around 4-5
13th Jan 2010 06:28 UTCBen Peters
The results will be delivered to me in about two week's time, and I will post-up then for anyone interested in some part-resolution to the conundrum! I would appreciate some help analyzing the Raman output, as I do not have any benchmark samples.
Many thanks,
Ben
13th Jan 2010 06:56 UTCTrish Wilson
Re the boulders -- these are in fact ones that have been loved in Neolithic times, when they were gently shaped into mountains, and then again when they came to light much more recently, and the faces repolished. They are too heavy for me to lift, but I managed to get a couple of pictures using the flash, in a room really not conducive to good photography, of part of the unpolished area where the surface crystals are visible. I thought you may be interested in seeing this.
We have a large collection of Chinese archaic jades, and the variations in the nephrite used is amazing. Not having a background in geology, this is not easy to fully understand or convey. In some cases, where weathering is excessive, the felted texture of the nephrite is clearly visible to the naked eye.
I don't wish to bore the members here with too many pictures of jade artefacts. If you or any of the other members are interested in seeing more and discussing the subject further, I would be happy to oblige privately. jade@scs.brisnet.org.au
13th Jan 2010 08:42 UTCBoris Erjavc
Here is one of my serpentinite.
Boris
13th Jan 2010 09:12 UTCTrish Wilson
13th Jan 2010 21:37 UTCEzekiel Hughes
....The darkened areas shown here are comprised of Manganese deposits and in-situ burial soil that had adhered to the finished piece during its interrment for thousands of years in a burial environment. In the replications, these ‘deposits’ are now usually glued or waxed onto replicas made from a conglomerate of minerals, with burnt-on sugar or black paint ’specks’, to represent the Manganese, and the obligatory mud slurry that seems to accompany almost all faked items. When one is viewing a true artifact, these deposits are permanently adhered to the surface, as they literally become ‘one’ with the burial object and resist all attempts to remove them, short of re-grinding the jade or stone object.....
Timeless jade
of course those deposits are very, very tiny...(see attachment: "Manganese Crystalline Formations Ang Estate Fenghuang" ) ...and sense Trish already confirmed it's pyrite on that piece, that cannot be what we are seeing...and of course shouldn't be carved....rather this neatly explains why someone would try to fake the look...getting a little carried away I imagine.
3rd Feb 2010 01:16 UTCEzekiel Hughes
-------------------------------------------------------
> Here I am again commenting on a few items that
> bother me - my background again is a geologist
> with several years experience mining and studying
> nephrite. I do not speak about jadeite.
> The first specimen with the pyrite cubes - to me
> these are phenocrysts which likely formed by a
> diagenetic process, not the metasomatism that
> forms nephrite.
> The river boulders definitely look like nephrite
> and the weathering is what I would expect to see.
> Most of the artifact pictures don't look like
> this.
> I agree with others comments that the level of
> weathering suggested by the pictures should affect
> the pyrite more.
> I took another look at the EBay nephrite/pyrite
> from New Zealand - this looks like later
> emplacement on a fracture - there is alteration
> along the fracture supporting this observation.
> The mention of weathering showing the felted
> texture of nephrite - an SEM (scanning electron
> microscope) is required to see texture in
> nephrite. If coarse enough to see on surface it
> could still be the tremolite/actinolite
> composition.
> Other inclusions common in nephrite are chromite
> (steely gray polished) and ilmenite - this could
> be the resistant brownish patches on the
> antigorite carving.
> I still have not found a reference positively
> identifying pyrite as an inclusion in true
> nephrite.
>
> Disclaimer - my opinions only based on pictures
I got a tidbit of information on the New Zealand occurance some might find interesting...or not:-) but here is the quote from someone I asked from the area:
This stone is an oddity and a unique occurance here in NZ. It only comes from one source, D'Urville Island at the top of the Sth Isld. The area is only accessable by boat and in notoriously dangerous seas. Very little workable material to be found which is probably why not much of it has ever been seen. As Dallas says above, small pyrites are relatively common, particularly in SthWestland stone but not in the size of that example. Cant help you much on the technicalities of formation, but the darkers areas on the stone look to me to be simply discoloured nephrite rather than any other mineral. Not sure about serpentine presence but I know the island was mostly visited in antiquity for its dark tool-grade argillite. Maybe the contact with this caused the unique attributes of this specimen?
The serpentinites in the area are noted for thier high pyrite content, which I guess goes along way to explaining it. I can't afford to pay for journals, so that's all I can find out.
~Zeke
7th Feb 2010 22:09 UTCTrish Wilson
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=310198308557&ru=http%3A%2F%2Fshop.ebay.com%3A80%2Fi.html%3F_adv%3D1%26_nkw%3D310198308557%26_in_kw%3D1%26_ex_kw%3D%26_sacat%3DSee-All-Categories%26_okw%3D310198308557%26_oexkw%3D%26_udlo%3D%26_udhi%3D%26_ftrt%3D901%26_ftrv%3D1%26_sabdlo%3D%26_sabdhi%3D%26_samilow%3D%26_samihi%3D%26_sadis%3D200%26_fpos%3DZip%2Bcode%26_fsct%3D%26LH_SALE_CURRENCY%3D0%26_sop%3D12%26_dmd%3D1%26_ipg%3D50%26_fvi%3D1&_rdc=1
I would have been interested had it been from China. We have seen numbers of this dark nephrite jade in archaic carvings, however, the percentage that have pyrite inclusions is very small, so the occurrence is rare.
We have not been able to have it tested as yet, but this will happen.
Trish Wilson.
7th Feb 2010 22:15 UTCTrish Wilson
Trish Wilson.
7th Feb 2010 22:33 UTCEzekiel Hughes
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Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2024, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters. Founded in 2000 by Jolyon Ralph.
Privacy Policy - Terms & Conditions - Contact Us / DMCA issues - Report a bug/vulnerability Current server date and time: March 19, 2024 07:35:24