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Identity HelpNephrite or Jadeite?

21st Oct 2012 22:31 UTCAnonymous User

Hay hounds,

This 32lb boulder was found in the Eel River CA in Mendocino county (higher in the mountains near latonville). It was embedded deep in a cliff made of piled stones about 50 feet down in the river bed itself. The structure under a loupe is certainly a great deal tighter than that of another piece I have (certified nephrite from the same river) but is also more granular looking, yet still semi fibrous. I have heard the ring of nephrite and jadeite, and grossular garnet, etc. This rings at a clear high pitch, so much so that rubbing fingers on the outside skin make the entire 30 pounds sing.

Moh's of the deep green flame like spots is 6.7, and the bright green varies from 6.7 to a 7.0 (equal to a piece of clear quartz I have.)

There are a few clear spots and some tiny translucent veins that are tightly wound throughout and match the colors of the solids.

Also, note that I did find 3 riverworn chunks of chloromelanite jadeite in the same river bed cliff no more than 100 feet away in any direction.

Thanks for the help in advance, I would like to do a gravity test, but I am in no way a mathematics wiz and would therefore most likely screw it up.

22nd Oct 2012 01:43 UTCOwen Lewis

Hi Bo,

Can't be sure of anything from your pics - but I'll guess that Jadeite is a definite possibility :-) Colour looks exciting, As you probably know there is a find of Jadeite maybe 50 miles inland, on the other side of the watershed, at Clear Creek.

Assuming it is Jadeite, it's value will vary widely according to translucency, colour and flaws. Given the possible value, I'd definitely invest in sending a few small small samples to G.I.A. in Carlsbad, CA for an expert view on the quality.

As to whether it is or is not Jadeite, XRD should be determinative - as will be some combination of microscopy, RI and SG determination. There are several other optical tests too that might give useful information on your stuff (spectroscopy and UV fluorescence in particular). If you need someone to prepare a small sample for RI testing, PM me for a steer to a friend in California who can help you out.

Good luck!

Owen

P.S. Not quite sure how you'd arrive at a Mohs's scale reading of 6.7. Would that be 6 - 7?

22nd Oct 2012 17:44 UTCAnonymous User

Owen,

The 6.7 came from scratch testing done with nephrite, agate, quartz, and peridot. I found the happy medium by how much was scratched, and how much was not. In all honesty it could be a little more or less, but through out it is certainly harder that 6.5 and never harder that 7.0. At first I figured it was Idocrase or a pyroxene rich diopside, but that seems far fetched without the presence of aluminum. I may not be an expert, but most all pyroxene has aluminum or sodium or magnesium or chromium, so for all of those to be present in the same place at the same time but not form any sort of jadeite yet create all these other pyroxene forms. . .?

Yes, I suppose some real tests would be in order.

22nd Oct 2012 18:28 UTCAnonymous User

When looked at after a polish it looks identical to this in every way down to the smallest clouded detail: http://www.mindat.org/loc-221183.html

22nd Oct 2012 23:06 UTCOwen Lewis

Bo Hulse (2) Wrote:

-------------------------------------------------------

> The 6.7 came from scratch testing done with

> nephrite, agate, quartz, and peridot. I found the

> happy medium by how much was scratched, and how

> much was not. In all honesty it could be a little

> more or less, but through out it is certainly

> harder that 6.5 and never harder that 7.0.

>

> Yes, I suppose some real tests would be in order.

Mohs's scale of hardness has been around for almost two hundred years. It endures because scratch testing against this ten-point scale provides, in the field and essentially with no equipment, an *indicator* not to what a mineral is but to what it *cannot* be and thus which can be eliminated from consideration. The scale is, quite deliberately I think, extremely crude with only 10 points of reference. These points are not linearly spaced or spaced in any other predictable separation (e.g. logarithmic). Provided that the the scale is only used as its inventor intended it has value, albeit a limited value. The moment users attempt to 'gild the lily' by convincing themselves that they can refine the outcome of a test by inserting decimal places between the ten values stipulated by Mohs, error and 'wish fulfillment' begin to replace solid pragmatic assessment. Not only is there no rationality in the spacing of the ten points on Mohs's scale (beyond 1 being the least hard and 10 being the most hard and with each value being reliably and repeatedly found in crystals of one stated mineral species) but the likelihood of experimental error prevents meaningful use of Moh's scale for other than this crudest of separations by hardness.

Consider the following:

1. Though this not as widely understood as it should be, many minerals do not have a single measure of hardness. Rather their hardness (even given standard test conditions) can alter radically with the direction on the crystal in which the scratch is placed. Two sobering examples are (a) Kyanite, where uniformly conducted scratch tests can return a Mohs's scale value of anywhere from 4 to 7. (b) Diamond type IIa, on a single crystal of which the true hardness (not determined until the 1980's) can vary by more than the accurately measured variance in hardness between Talc (Mohs 1) and Corundum (Mohs 9), just depending on the direction of the scratch.

2. To conduct an accurate scratch test for hardness (still used at the cutting edge of materials science) the results must be repeatable. This requires (a) the preparation of uniformly planar surfaces on crystals under test. (b) Styluses of known and uniform hardness and dimensions. (c) An accurately metered force applied to a stylus which shall transmit that force at a uniform angle (90 deg) to the surface of the test material.

None of which in any way knocks the possibility that Bo's boulder might be Jadeite.

25th Oct 2012 06:45 UTCAnonymous User

Owen Lewis (2) Wrote:

-------------------------------------------------------

> Bo Hulse (2) Wrote:

> --------------------------------------------------

> -----

>

> None of which in any way knocks the possibility

> that Bo's boulder might be Jadeite.

Well sir, you seem vary hostile for a min-man. I asked what readers thought, not what they didn't. You can see cleavage and the like from the images, vein patterns, etc. . .Am I not in the help section? Do you not have advice beyond 'mail me some.' I have a valid argument, moh's aside, so can we get to something more?

Also, gravity of the specimen in question is 3.26. The magic of a scale, water, and air. Don't get me wrong, I am all for knowing, but best with my eyes and ears -- not an X-ray. Can't take that out on a weekend 50 mile hike carrying over 120lbs of find, plus gear.

Thanks for the 'wow' factor duh advice.

25th Oct 2012 16:16 UTCOwen Lewis

Bo Hulse (2) Wrote:

-------------------------------------------------------

> Owen Lewis (2) Wrote:

> --------------------------------------------------

> >

> > None of which in any way knocks the possibility

> > that Bo's boulder might be Jadeite.

>

> Well sir, you seem vary hostile for a min-man.

Sorry you conclude that. See later

> You can see cleavage and the like from the images,

> vein patterns, etc. . .Am I not in the help

> section? Do you not have advice beyond 'mail me

> some.'

If you can see cleavage in your stuff then its not Jadeite which never cleaves. Sorry if that sounds like 'what I don't think' but, in my view, the identification of stones by physical and optical properties is one of elimination of 'impossibles' rather than of leaping straight to some final conclusion of ID. It's be fair to add that the greater the experience, the quicker and often easier this process becomes.

In the case of 'cleavage, you have one of the 'impossibles' If what you see is cleavage then your stuff cannot be Jadeite. Ende. You sure you have cleavage? In your first post you said the sample was 'semi-fibrous'. Jadeite commonly has a granular characteristic, no cleavage and a fracture that is 'granular to splintery'.

> I have a valid argument, moh's aside, so

> can we get to something more?

>

> Also, gravity of the specimen in question is 3.26.

> The magic of a scale, water, and air.

That reading is at the very low end of the generally accepted Jadeite range. As recently discussed in another thread, Jadeite is only sometimes found in pure form. Commonly, a specimen may somewhere along the Jadeite-Diopside solid solution series. So Jadeite (along with Almandine, Scapolite and quite a few others) is a gem stone whose fit of ID to SG is a lot sloppier than, say, the acceptable SG ranges for Diamond or Rock Crystal which are really quite tight. Also,where a sample is not transparent/translucent, it is not possible to be sure that the sample is not concealing different material(s) within it.

Burmese Jadeite boulders are usually sold whole at auction. This has been described by one leading Jade expert as 'high-end gambling', Buyers can only know the real value of their purchases when they are cut up :-)

>Don't get me

> wrong, I am all for knowing, but best with my eyes

> and ears -- not an X-ray. Can't take that out on a

> weekend 50 mile hike carrying over 120lbs of find,

> plus gear.

You have the advantage of having seen and handled this boulder. The rest of us have only some soft-focus pics and your statements about your find. For myself I can go no further than as below. Others may feel that they can give you a more detailed opinion.

- The green on white mottling is interesting, being sometimes found in some Jadeite.

- Geologically, the location seems possible - and you say you have already recovered samples of a variety of Jadeite from the same locality.

- SG and hardness are inconclusive.

- So send a sample for analysis? But if your stuff really demonstrates cleavage don't hold your breath waiting to hear 'Jadeite'.

> Thanks for the 'wow' factor duh advice.

You're welcome. If you would explain how you determined a Mohs's scale value of 6.7 and the significance of the decimal place I will read that with full attention.

25th Oct 2012 16:38 UTCD Mike Reinke

Bo,

I really don't think Owen was being hostile. It may seem from a lengthy explanation that he was 'showing you that you were wrong', when he was really just carefully clarifying why there are no decimal points in the Moh's scale. I found the explanation nicely concise. Also he did mention the color was' exciting' and that he was not knocking your find. The big drawback to threads is that they can be soooo easily misunderstood.

Your 32lb. piece is exciting. I beachcomb Lake Michigan,and I've found a maybe 6 oz piece of what-might-be jade that washed up last year. It can't compare to your find, but it is all still fun...

26th Oct 2012 02:34 UTCAnonymous User

The sentence should have read "Can you see cleavage?" My rambling on took the value of the question mark away :( Honestly I see nothing of the like and when it breaks there is no rhyme or reason to it. here are some better photos.

Also, if it is what some suspect it to be (the high pyroxene diopside) than it will have the same refractive index. Is this the test you speak of? And if so, what other tests did said party do to determine that there is no jadeite in the Eel River?

Looking at the images, it does look granular to me, with the naked eye at least. Any ideas on what else it could be?

I assumed the Moh's scale had decimal points. I see geologists use 5.5-6 or whatever combination and figured it was so. I came to 6.7 by taking a nice clear quartz (7.0) and a stainless steel blade, feldspar, nephrite glass onyx, idocrase, etc. . . long story short I compared direction, depth of marks on each, and did so many times so the pressure would reach some sort of average. I though there were tools of some kind that did this with ease. . . It was a fun sort of puzzle, to bad it was a worthless endeavor.

26th Oct 2012 02:56 UTCPaul Brandes 🌟 Manager

In mineralogy (and geology for that matter), usually the simplest explanation is the best. In the case of Moh's hardness scale, there are decimal points as you state Bo, but we keep it to only 0.5 to keep things simple. I'm sure quartz is likely between say 6.7 and 7.3 for hardness, so why not make it simple and just say 7?? There was nothing wrong with you did Bo, in fact your work ought to be commended because you actually took the time to test your unknown.

I'm no expert on jade, so I won't speculate on what you might have. Your specific gravity certainly is close to what jadeite is, however. You may want to take Owen's advice and either send a sample or two off to be analysed, or take some smaller pieces to a nearby university geology department for examination.

Good luck! (tu)

27th Oct 2012 13:20 UTCRalph S Bottrill 🌟 Manager

Owen is quite fair and correct, when you suspect a rare mineral like jadeite there is no substitute for a good analysis, it may not be monominerallic, so SG and hardness will not cut it.

29th Oct 2012 18:18 UTCAnonymous User

Hay hounds,

The identity of this specimen has been RESOLVED! What we have here is Diopside-Omphacite-Jadeite-Microcrystalline Chalcedony. I was told that it is not at all unheard of (marketed as Siberian Jadeite often, Maw-sit-sit with noticeable semi translucent white and light green, etc.) and the mixture can vary even more.

29th Oct 2012 20:26 UTCEugene & Sharon Cisneros Expert

Bo,

After following this thread through, it would be informational to know by what means and by whom this has been resolved.

Thanks,

Gene

12th Dec 2012 06:07 UTCEzekiel Hughes

It is a botryoidal nephrite +/- diopside in my opinion...I believe I told this to the seller, or at least that it was nephrite not jadeite unless it was the first of it's kind....or a similar claim from the same area.

12th Dec 2012 23:56 UTCBart Cannon

The electron microprobe can answer this question in a heart beat.

The two micron beam diameter and x-ray spectral production confirm jadeite vs. nephrite quite easily. Their chemistries are not even close.

I have collected Russsian River jadeites. No one would be confused about their stereo microscope observations regarding their identity as different from nephrite (actinolite)

I've been dealing with this question for thirty years.

Bart

13th Dec 2012 18:09 UTCOwen Lewis

Bart,

Agreed. Even using less technically advanced techniques, the successful differentiation of Jadeite from Nephite should not be hard.

Given Mother Nature's mucky workshop, how well does an electron microprobe deal with the differentiation of mineral varieties within a solid solution series?

Thanks.

Owen

3rd Feb 2015 17:12 UTCArthur Browne Jr.

Here is the image.

If anyone is interested. It comes from a 20lb boulder.

Arthur

{ Attachment 56977 Unavailable! }

3rd Feb 2015 19:25 UTCOwen Melfyn Lewis

Pic won't display for me for some reason :-(

3rd Feb 2015 22:52 UTCArthur Browne Jr.

Here is the image.

If anyone is interested. It comes from a 20lb boulder.

Arthur

3rd Feb 2015 23:59 UTCOwen Melfyn Lewis

Between the two, a careful SG determination will sort it out. Because of the (near opaque?) nature of what you show, the SG of a single piece should not be relied on. Rather, get the SG of, say, ten pieces; discard any obvious outliers and take the average of the rest.

The SG ranges of nephrite and jadeite, respectively, are 2.95 (+0.15 - -0.05) and 3.34 (+0.06 - -0.09). There should be no overlap so such averaged SG's across several samples should be a reliable indicator. To do better, also cut and polish a flat on a piece and determine the RIs and birefringence.

Guessing off you pics alone, the colour says nephrite to me.

9th Dec 2016 06:37 UTCDonald Kasper

Reflectance infrared of two white to green samples sold as Eel River jade were found to be diopside with clinochlore veining in one, and just diopside in the other, matching the look of the first thread picture for the diopside specimen I bought. Hardness, streak, specific gravity, etc are innacurate and a waste of time in identifying nephrite and jadeite. The only jadeite in the state is located out of Clear Creek, CA, west of Coalinga. I doubt there is any NW California nephrite. I do have one and only one nephrite sample that came out of the Happy Camp region in NE California, all others being various green silicates including antigorite, lizardite, talc, zoisite, diopside, actinolite, vesuvianite, and clinochlore. NO, a careful specific gravity test will not sort it out as jadeite and antigorite var willismsite have the exact same specific gravity and hardness and look.

9th Dec 2016 06:42 UTCDonald Kasper

Reflectance infrared conclusively differentiates nephrite from jadeite, and from all other green serpentine body minerals. Microprobe is vastly more expensive for no reason. In particular, the method differentiates nephrite from antigorite and lizardite.

9th Dec 2016 07:58 UTCAlfredo Petrov Manager

"a careful specific gravity test will not sort it out as jadeite and antigorite var willismsite have the exact same specific gravity"

This is not true, as jadeite's specific gravity is very much higher than antigorite's, so much so that even the crudest of density measurements would separate them easily. I know nothing about the so-called "williamsite" but, if it's specific gravity and hardness are really the same as jadeite's then "williamsite" can not possibly be a variety of antigorite and it needs to be studied again by a real mineralogist.

9th Dec 2016 11:08 UTCJoel Dyer

Interesting find whatever it is confirmed to be.

As for hardness measurement, I myself have used a Hanneman Microhardness (APO 32x) device in connection with a Metallographic Inverted Microscope. With this Vickers Hardness can be measured, and the produced values are a completely different story compared to the very vague, unscientific Mohs hardness scale.

The device contains a faceted diamond point and a "weight" or "force scale". The diamond point creates an indentation in the tested material, and specific, recommended or fixed force levels on the readout are used for each tested material, so that the results will be usable and comparable. The test or "stress" times are the same for different materials, say 10 or 20 seconds or another agreed time window, again, so that the results will be usable and comparable.

The cross-measurements of the repreated indentation pits are measured, and and average taken. Then the measurements are entered into a formula, which will then give the Vickers Hardness.

Many minerals and metals might share exactly the same Mohs hardness, but have very much differing Vickers Hardness values. This kind of hardness test is standardardised & there are "Vickers" and equivalent devices that give also straight readouts.

Addendum: Vickers and similar type hardness values are usually expressed as value ranges, due to slight differences in chemical composition & other structural details.

Vickers hardness readings are also subject to crystallographic hardness differences, ie. differential hardness. Readings obtained form one highly polished crystallographically oriented surface may vary from other crystallographically oriented values: examples are kyanite, diamond (yes!) etc etc.

Mohs is simply a very rough, relative scale, no more: a kind of "quick and dirty" test to perhaps eliminate some possibilities.

Cheers,

9th Dec 2016 11:34 UTCOwen Melfyn Lewis

Alfredo Petrov Wrote:

-------------------------------------------------------

> "a careful specific gravity test will not sort it

> out as jadeite and antigorite var willismsite have

> the exact same specific gravity"

>

> This is not true, as jadeite's specific gravity is

> very much higher than antigorite's, so much so

> that even the crudest of density measurements

> would separate them easily. I know nothing about

> the so-called "williamsite" but, if it's specific

> gravity and hardness are really the same as

> jadeite's then "williamsite" can not possibly be a

> variety of antigorite and it needs to be studied

> again by a real mineralogist.

+1.

Add to which DK needs to read more carefully. I said that, properly conducted, SG testing is a sure differentiatior of jadeite from nephrite. And so it is (though no ID can be positively made from evaluating a single characteristic alone.

As for 'infrared reflectance meters'. Well made, these have a narrow range of application in assisting with identification of some cut and highly polished gemstones. In the hands of the unknowledgeable (as they are to often are) they simply delude and mislead. Because mineralogists usually work with broken, rough material or unpolished crystal forms, I suggest that reflectometers should be strictly avoided by them.

9th Dec 2016 13:09 UTCJoel Dyer

Owen: can I assume that your recommendation regarding the use of digital "refractometers" (sic) concerns only mineralogists - professional and amateur - who have not dwelved and do not dwelve into gemmology & the proper use of various gemmological tools for gemstone - and thus often mineral - identification?

There are always some "freak" mineralogists that might be tempted to "step into enemy territory" and study also gemmology ;-). Personally, just as an example, I'm currently studying an Advanced Gemmology course, after completing the Basic course...and am very thankful for the lessons learned.

Highly polished small, "non-gemstone" mineral slices or pieces can be identified using the same tools that "applied mineralogists" (ie gemmologists) use for their daily work.

Once upon a time, skilled and patient "usual" or ""normal"" mineralogists used to practice more traditional optical mineralogy. C. S. Hurlbut for instance was a master of using "enemy tools".

Nowadays, as we know, certain types of microscope & identification work have diminished a lot, and into the picture has heavily entered XRD, EDS/WDS, microprobe LA-ICP-MS and so on. Sad, because many traditional tools are useful, if the trouble of studying and practising this art properly is just taken.

Cheers,

10th Dec 2016 16:43 UTCOwen Melfyn Lewis

Joel Dyer Wrote:

-------------------------------------------------------

> Owen: can I assume that your recommendation

> regarding the use of digital "refractometers"

> (sic) concerns only mineralogists - professional

> and amateur - who have not dwelved and do not

> dwelve into gemmology & the proper use of various

> gemmological tools for gemstone - and thus often

> mineral - identification?

> Cheers,

@ Joel,

The accuracy of these devices is much dependent on their design, build quality and that tested specimens having a very highly polished and planar surface necessary for accurate testing by this method. The user should also have a good understanding of Fresnel's Laws.

Their best use in gemmology is restricted to gems with an IR above 1.81 that can't be measured by the conventional totally internally reflecting design of refractometer. I do not own one and have yet to feel the need to own one (at least since I was *very* wet behind the ears).

The quality of the polished finish of a tested surface is critical and I imagine should, by itself, disqualify this method from the testing of mineralogical samples.

11th Dec 2016 07:27 UTCJoel Dyer

Hi Owen,

Thanks for your input. Except for mostly a single comment, I would have avoided continuing to discuss this subject off track to its original subject. I feel that other mineralogists deserve a clarificiation. If you are interested in discussing the matter more in details, maybe you can PM or email me?

You said that for using digital reflectometer-refractometers one should dwelve into Fresnel's laws, but said nothing about that requirement when using traditional refractometers: why? Users of any instrument in my opinion require proper knowledge of a devices capabilities and wekanesses, and of how to operate the device. This goes for SEM-EDS, microprobe and other work, too, as well as driving a car, to take a mundane example.

The most disturbing comment was that you claimed that when using digital meters for testing, mineralogical - gemstones mostly are minerals - samples are disqualified. I would not have expected you to make such a comment, with your extensive experience and knowledge, for which I have a lot of respect.

Surely, Owen, you are aware than many mineralogists still use polished sections and thin sections for precise anlytical investigations? If you've read the instructions for such work, and have carried out such work yourself, you will be aware, that mineralogical samples require a very high, good quality polish? This is particularly important for microhardness testing and extremely important for reflected light ore microscopy.

If one can polish small mineral pieces up to 0,25 or 0,05 micron and test them very successfully with a traditional refractometer, I have no doubt these samples can be tested, if they meet the size requirements, using a digital device.

I must point out, that the main reason for anyone using a digital measuring device should - in my humble opinion - be to roughly sort out samples with RI values over 1.80, or in the below situations. Limitations of the devices should also be very clear to the operator, and calibration should be carried out regularly.

A professional gemmologist-minrelogist with over 40 years' experience has told me that many times a digital meter is the only tool you can take to public happenings, due to regulations concerning poisonous liquids etc. What would happen, if some young, busy child accidentally knocked over your bottle of RI liquid & it broke all over the floor? This could cause serious trouble, as well as the fact there hardly will always be suitable venting that' s preferable for toxic fluid use.

I've also heard that many gemmologists carry a digital device on testing or buying trips for similar situations where a traditional desktop refractometer is impractible, but that many gemmologists keep quiet about this. Back in the hotel values can always be double-checked with other instruments. Who, in their right mind, would ever use a single tool to identify anything, anyways?

But perhaps we can discuss this matter more in detail via email. I'm personally waiting for a newer model of a digital device, which I am to use thorougly, putting all measurement data for gemstones and mineralogical samples in a spreadsheet. It is best to test things thoroughly onself before condemning something altogether for any particular purpose, no ? :-)

Cheers,

11th Dec 2016 14:20 UTCOwen Melfyn Lewis

Joel Dyer Wrote:

-------------------------------------------------------

I feel that other mineralogists deserve a

> clarificiation. If you are interested in

> discussing the matter more in details, maybe you

> can PM or email me?

Forgive me. These last couple of months, my e-mail/other posting output has reduced to almost nothing, other than those required to service urgent personal needs. The now terse little bits I post here will have to do for the forseeable future.

> Surely, Owen, you are aware than many

> mineralogists still use polished sections and thin

> sections for precise anlytical investigations? If

> you've read the instructions for such work, and

> have carried out such work yourself, you will be

> aware, that mineralogical samples require a very

> high, good quality polish? This is particularly

> important for microhardness testing and extremely

> important for reflected light ore microscopy.

>

> If one can polish small mineral pieces up to 0,25

> or 0,05 micron and test them very successfully

> with a traditional refractometer, I have no doubt

> these samples can be tested, if they meet the size

> requirements, using a digital device.

> I must point out, that the main reason for anyone

> using a digital measuring device should - in my

> humble opinion - be to roughly sort out samples

> with RI values over 1.80, or in the below

> situations. Limitations of the devices should also

> be very clear to the operator, and calibration

> should be carried out regularly.

My assumption is that only a very small percentage of mineralogists are now also active petrologists although rather more may once have learned those skills years ago. If I am wrong in assuming that high quality thin slice preparation is no longer practiced by most mineralogists, then mea culpa.

> A professional gemmologist-minrelogist with over

> 40 years' experience has told me that many times a

> digital meter is the only tool you can take to

> public happenings, due to regulations concerning

> poisonous liquids etc. What would happen, if some

> young, busy child accidentally knocked over your

> bottle of RI liquid & it broke all over the floor?

> This could cause serious trouble, as well as the

> fact there hardly will always be suitable venting

> that' s preferable for toxic fluid use.

Pish and wibble ;-) The indispensible tools to carry everwhere are a sharp and experienced eye, a trained mind - and a good knowledge of the 'Visual Optics' methodology, developed by Alan Hodgkinson and published by him and also (sporadically) by Bill Hanneman.

>

> But perhaps we can discuss this matter more in

> detail via email. I'm personally waiting for a

> newer model of a digital device, which I am to use

> thorougly, putting all measurement data for

> gemstones and mineralogical samples in a

> spreadsheet. It is best to test things thoroughly

> onself before condemning something altogether for

> any particular purpose, no ? :-)

To each their own. As said, I turned away from getting one. In my view, the method is inherently the less accurate in the results it will return. I never have had reason to regret this choice (else I would, long ere now, have bought one).

But key to this discussion is that a reflectometer is of no use to mineralogists, other than the minority who currently engage in the preparation of polished thin sections - lots (hundreds) of them.

11th Dec 2016 20:35 UTCReiner Mielke Expert

" If I am wrong in assuming that high quality thin slice preparation is no longer practiced by most mineralogists, then mea culpa." Yes you are wrong, even more so when it comes to polished sections.

12th Dec 2016 00:32 UTCD. Peck

I note, Reiner that you have specified "mineralogists" as no longer using thin sections. I wonder though if they are still not fundamental in petrology? As to polished sections, I would think that mining geologists would still find them useful.

12th Dec 2016 11:34 UTCReiner Mielke Expert

Helo Don,

Wasn't me who said that I was quoting Owen. Thin sections are still an essential component in petrology and tool for mineralogists who study petrology.

12th Dec 2016 11:56 UTCAlfredo Petrov Manager

Incidentally, the cheapest way to distinguish nephrite from jadeite is to check its fusibility! All one needs are a tiny splinter of the rock, tweezers and the kitchen gas flame. (Those poor sods with electric kitchens should toss them and get a gas range. Gas kitchens are essential for mineralogy!)

I understand this technique might not be so useful for gemmologists. ;-)

12th Dec 2016 13:12 UTCJoel Dyer

Alfredo, that's a good one :-) . Got a torch that goes up to about 900 celsius or so. Must try the method one day when I get a raw piece of jadeite, as don't want to destroy the single jadeite ring that got for gemmological practise, from a senior gemmologist who didn't seem to mind my butting my behind into gemmologists's business, perhaps because he was paid to give me support...

Speaking about usability, the Hodgkinson eyeball technique etc. will probably not work for translucent material or mineralogical thin / polished sections. But it's absolutely true that nothing can replace a long working experience & proper respect to this is due & given. Hats off to all hard work that has produced long-term, useful experience-knowledge.

Hopefully, mineralogists and gemmologists(=applied mineralogists+businessmen/women) can learn to get along together, without undue condescending attitudes, protectionism or whatever, letting each individual carry out cross-scientific and cross-cultural work in a fruitful and supportive way, and paying respect to the hard work of all persons involved.

Cheers,

12th Dec 2016 14:01 UTCOwen Melfyn Lewis

Reiner Mielke Wrote:

-------------------------------------------------------

> Helo Don,

>

> Wasn't me who said that I was quoting Owen. Thin

> sections are still an essential component in

> petrology and tool for mineralogists who study

> petrology.

We agree that thin polished sections are an essential for a petrologist. But is (these days) petrology considered to be an essential part of a mineralogists skill set by those under the age of (say) 50?

12th Dec 2016 14:11 UTCJoel Dyer

Hi Owen,

Who was talking about petrology in the first place? Polished minerals sections can be related to identifying minerals (including ore minerals) per se, not just when dwelving into petrological issues.

How can one necessarily identify many minerals in a sample properly using optical /analytical tools, if one doesn't have a well-polished surface? Sure, there are super-masters out there who never need a polished surface for anything, but there are more humble inquisitive persons needing some "device help" & also require surface preparation, which hardly takes more than 30-60 minutes for a small batch of material anyways. And photomicrography of some inclusions can become more possible & informative with a finely polished surface, not just using immersion liquids ;-)

Cheers,

12th Dec 2016 14:32 UTCOwen Melfyn Lewis

Alfredo Petrov Wrote:

-------------------------------------------------------

> Incidentally, the cheapest way to distinguish

> nephrite from jadeite is to check its fusibility!

> All one needs are a tiny splinter of the rock,

> tweezers and the kitchen gas flame. (Those poor

> sods with electric kitchens should toss them and

> get a gas range. Gas kitchens are essential for

> mineralogy!)

>

> I understand this technique might not be so useful

> for gemmologists. ;-)

Well, this gemmologist keeps on hand a small single-flame gas burner of the type mainly sold to cooks for caramelising the tops of cremes brulee etc.. In my view, a valuable tool for a range of gemmological purposes. FWIW an electric oven is as useful as or slightly better then a gas one. However, care needs to be used with either to avoid a very unwelcome build-up of toxic fumes in the kitchen when used . Low level heat treatment of (e.g.) amber and copal really needs to be done small-scale and in a well-ventilated facility.

12th Dec 2016 16:48 UTCOwen Melfyn Lewis

Joel Dyer Wrote:

-------------------------------------------------------

> ..... photomicrography of

> some inclusions can become more possible &

> informative with a finely polished surface, not

> just using immersion liquids ;-)

Most find that practice leads to useful moderation of ideas formed on the basis of learning the various theory. Personally, I'd say that the ability (for purposes of gem testing) to minimise reflection at a media boundary is generally of more value than improving the definition and uniformity of such a boundary.

Then there is a third method whereby neither the close matching of media RIs nor the working up of a highly polished boundary plane is used. This requires the specimen to be photographed in a polariscope. Depending on circumstances, either a good macro lens may be used with a polariscope or else a microscope with polariscopic accessories. Here is a well-included 7ct oval mixed cut spinel with the many reflections avoided as far as possible by the use of polarised light. This lighting also enhances the appearance of some of the inclusions (apatite +) by the colouration of their boundries with the spinel.

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