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Techniques for CollectorsRecomend a good lab?

31st Mar 2009 16:58 UTCMatthew Boeck

I want to find out what minerals are in a rock I have, The rock is only fantastic for its Spherulite crystals, there are no loose (cavity) structure as they are all locked in matrix. I had sent the material out for X-ray defraction (John Attard did this work- Hi John!) and the results where not too diagnostic. I want to know what is in this thing more than just Quartz and Feldspar. I also sent it in to ASU who did a Infra-red test and got more information but it too was not extremely diagnostic.

I was reccomended to send it to Virginia Polytech. But I dont know a contact there. I would also like to send it to Caltech to George Rossman of Tourmaline fame, but he does not know me. So in the interim I am looking for an in exspensive way to do:

1) Age testing

2) Thin Section Microscopy (cross polar)

3) Mineral and element identification.

I would know more about these rocks but for the last 14 years noone has ever seen it and I cant find any pictures (other than mine) on the internet of similar materials that werent created in a test tube or generated digitally with a computer algorythm. The material is washing up on a beach so I can't find the collection site. When I posted it to the Mineral ID I got almost no information on it. (I thought someone should know something...) as for now I am the world leading authority on this un-named/ un-known enigma rock group and I have over 500 specimens. If new I would very much like to name the material "quasarite" if known I would be just as happy to know (finially) what it is.

Any help would be greatly appreciated. Gentlemen, I realize I am in way over my head here and this is very potentially the wrong forum to ask these beginner questions. I had posted to the other forums and could not get an informed oppinion.

-Matthew Boeck

San Diego

31st Mar 2009 18:29 UTCDonald Peck

Matthew, it sounds like you suspect you have a new mineral and would like that fact confirmed. Firstly, it is an arduous and expensive undertaking. That said, if you wish to go forward, you need to contact a research mineralogist at either a university or a major museum. I think you would get a quick answer on whether to proceed.

1st Apr 2009 10:18 UTCSebastian Möller Expert

Hello,

As a mineralogy student (writing my diploma thesis on petrology) I would recommend you to take a sample to a University first to make a thin section. In a thin section one can distinguish at least the different minerals present, in some cases (feldspars for example) a mineral ID (albite-anorthite series xCa determination up to at least 5 %) is possible just by looking at it under a polarization microscope, but it requires good xls, not just thin fibers or needles.

Then, a XRF (X-Ray Fluorescence) analysis is much better on rocks than a XRD. With that method you can determine the contents of the main elements and major trace elements (Ba, Sr, Rb,....) of the rock.

With both the information on minerals and main elements you can probably define the kind of rock you have.

Age determination is rather difficult and expensive (and I doubt it would be done without a scientific interest). For a first determination one could use a mass spectroscopy (ICP-MS, laser ablation ICP-MS or similiar methods) to get the isotopic ratios of lets say uranium and lead or Rb-Sr.

Regards,

Sebastian Möller

1st Apr 2009 16:52 UTCAlfredo Petrov Manager

Matthew, you wrote: "I want to know what is in this thing more than just Quartz and Feldspar. I also sent it in to ASU who did a Infra-red test and got more information but it too was not extremely diagnostic." Why are you so sure there is something in here, other than quartz, feldspar, and a little hematitic colouring matter? Perhaps your analysts aren't finding any new minerals in it because there aren't any there?

Many years ago, when I was a geology student at SDSU, we looked at a large variety of (Jurassic?) metavolcanic rocks, which are widely distributed along the western foothills of San Diego county. I can easily imagine that some of the tougher, more silicified types must end up as cobbles on the beaches. I don't recall seeing any that looked exactly like yours, but it could be a silicified spherulitic metavolcanic.

You also wrote: "If new I would very much like to name the material "quasarite" if known I would be just as happy to know (finially) what it is." I doubt that any geologist would want to invent a new name for the rock. I agree that your rock is pretty, and it could be marketable for lapidary purposes. For marketing purposes you can invent any trade name you like, "quasarite" or whatever you prefer; you can even trademark it. But it would be strictly a marketing term; no geologist or mineralogist is going to give it any official sanction.

Cheers,

Alfredo

1st Apr 2009 20:47 UTCMatthew Boeck

Hi Sebastian,

thanks for the information on testing I am looking for a good University that will help in the thin section department. U of Hawaii does thin section prep. fairly cheap. I don’t know a lot about XRF is there a recommended thickness for the tests, or is that up to the tester to determine? I know that the testing can be prohibitively expensive, so I would like to go with the less expensive testing first. I hadn't though of checking the material for radioactivity....probably needed to especially if I am carrying it around all the time. Any thoughts on specific labs? I am in Southern California.

Hi Alfredo,

well the ASU results only plots the main minerals on a probability scale, then they allow you to view your rock in comparison to a library of; Igneous, Metamorphic or Sedimentary rock, here is a link for the igneous plot; http://ratw.asu.edu/newspectra/deconvolve/RATW08659.html?deconvolve=igneous

Each time the results came back with a different set of minerals, although Quartz and Feldspar were common between the 3 libraries which are fairly common results for many rocks tested there. In truth I am not too sure there is anything new here, I simply want a better test. These rock types mostly conform to the igneous rock library and I must agree too, there seems to be a metamorphic component also, but probably later. Metavolcanic is a good term and another geologist said they appear to be close to a rhyodacite which would fit. Yes, they are very silicified and glassy.

As for marketing, I am un-interested in doing marketing from a lapidary stand point. I would only be interested in a name when the material comes back with a new and unique chemical formulation- which is true for all new minerals. I would not expect a scientific study to name a rock, only a new crystal form. I am not in this for fame or fortune.

Looking in at the Mindat database on crystallization they don’t even have a crystal structure for spherulitics, and they are crystals although amorphous in a geometrical sense. Note they do have a page for dendrites which are just flat not (usually) rounded, and is no less complex than this form. There is a lot of study on this class of mineralization- The stuff is everywhere and extremely common, and economically unimportant. Conversley the Spherulites and their material forms are exceptionally rare and comparitivly rather very important in polymer physics (at least) and there seems to be a lot of study going on in thoery of their creation with very little actual material on hand.

Although there are analogous materials in the rock record, I am having a real hard time finding any similar materials. At worst it is just so common that there is no interest/ at best, it is something new to science that has been overlooked. I am getting familiar with the Spherulitic formation process, but I can’t seem to find a physical location where they had formed. The analogous materials I have seen are to dissimilar to be a good fit; snow flake obsidian, ocean jasper, chrysanthemum stones, human kidney stones, meteorites and deep sea plate materials with spherulitic structures are not a match. I know there is volcanic material that is similar, although again not a good match (yet). I am hopeful to find more soon and I will be publishing new pictures to help everyone understand the complexity of the topic.
(I know this part is a bit of a rant, and I am sorry) To date no one has any of this material, no one on mindat knows what it is, no one I have showed it to has seen any of it, no pictures on the internet are similar, everyone seems to have a good idea of what it might be but when I ask for data or photos- no one has any. If you see my point I need a place to start to understand this material other than a vague grouping of 'might be, could be, possibly is, probably, I think, looks like' and other misc. conjecture. (ok rant is done)

As for my short term goals I am looking for a good lab to do study that is accurate (not general) I thought a recommendation would be better than just opening the phone book and calling at random. I am looking for locations, addresses, names, phone numbers, emails....anything I can get. And not to be negative I want you all to know how so very appreciative I am for any and all help, critical or otherwise.

Thanks again,

-Matt Boeck

1st Apr 2009 22:28 UTCSebastian Möller Expert

Hello,

XRF is usually done with a powdered sample (just one small representative part of a specimen of a few grams is sufficient). It is either pressed to a pill or molten (with lithium borate as a flux).

I do not know a good lab for that method in the US (have used the equipment at Kiel university, where I study). Maybe one of the US mineralogists around can recommend you one. XRF is a method used quite often in determination of volcanic rocks, so Hawaii University maybe has a unit, as well as the Geological Survey.

Regards,

Sebastian Möller

2nd Apr 2009 19:04 UTCPeter Haas

XRF has the big advantage to tell you quickly, which elements are major (i.e. > 10% by weight), minor (1-10% by weight) or trace (< 1% by weight) constituents of a sample. This test is relatively cheap, since it requires not much extra work, except for the sample preparation. Some of the labs which are equipped with an XRF instrument may perform such tests routinely, and they also routinely perform the sample preparation work. This might reduce the price for you when this is just the test you want. It also means, however, that the analysis is considerably more expensive, when your sample needs to be prepared in a different manner or requires a somewhat different measuring program.

If you want accurate quantitative results, XRF is not the technique of choice. Unless your sample closely fits the composition of another material frequently analysed by the lab in question (as I understand from your writing, this seems not to be the case), a new calibration will have to be set up. Calibration in XRF is difficult (and expensive), because the response factors strongly depend on the composition and physical properties of the matrix.

Accurate whole rock averages are more easily obtained by ICP/OES or ICP/MS or a combination of both, after appropriate digestion of the sample. The matrix these instruments are actually fed with is a dilute aqueous solution with defined pH and ionic strength, so calibration is easily performed with reference solutions prepared from soluble compounds of the respective elements. Also, modern ICP instruments are equipped with measuring programs that allow for simultaneous determination of several tens of elements in a single run, reducing analysis time and costs.

You may also ask chemical companies: most of the larger ones have central analytical labs which likely are equipped with not just one of the instruments mentioned. Although not all of them are advertising, many of them are willing to work for external customers when they are asked. They also can help you in finding the best technique for your needs.

3rd Apr 2009 15:41 UTCDonald Peck

Peter, what are ICP/OES and ICP/MS? These are new to me.

3rd Apr 2009 18:22 UTCPeter Haas

ICP stands for "inductively coupled plasma". In simple words, it is a high temperature flame (~ 6000-8000 K) which is generated by action of a high frequency alternating current (~ 80 MHz) on an appropriate gas, usually argon. At this temperature, any sample disintegrates to isolated atoms of the elements it is composed of. Also, due to the high temperature, a fair amount of these atoms will form element ions.

In ICP/OES (or, ICP/AES - OES and AES stand for optical emission spectroscopy and atomic emission spectroscopy, respectively), the plasma burner is combined with a spectrometer. The plasma acts as a source for excited ions, which will emit photons when they return in the ground state (excitation occurs by collision of the ions with other particles that move at high speed and transmit considerable amounts of kinetic energy). The wavelength and the intensity of the emitted light are recorded in the spectrometer. In ICP/MS, the burner is combined with a mass spectrometer and acts just as the ion source.

ICP/OES and ICP/MS yield complementary information, from an analytical point of view. Some elements, such as the alkali metals, give higher responses in the OES mode, while others are more sensitively detected with the mass spectrometer. A drawback of ICP/MS are isobaric interferences; the pair ArC+/Cr+ is one well known example: ArC+, a molecule ion that forms in the plasma when organic matter is analyzed, interferes with the chromium signal. To solve this problem, high resolution mass spectrometers have to be used. For a long time, high resolution was only possible with sector field instruments, but, apart from being utterly expensive, these are vere sensitive to pressure and this made the construction of an appropriate interface rather difficult. Other high resolution instruments (FTMS, TOFMS) became broadly available only in recent years, but they are not much less sensitive to pressure and also not much less expensive (> 300,000 $).

4th Apr 2009 14:49 UTCDonald Peck

Thank you, Peter. Interesting instrumentation. My degree in chemistry is anachronistic. I graduated before the instrumental explosion and am pretty much a wet-chemist.

6th Apr 2009 19:46 UTCMatthew Boeck

Wow! a lot more information to discover here! I had to go to Wikipedia to figure some of it out. thanks again for the posts I am heading in a new direction now. - Matt B. PGMC

6th Apr 2009 20:26 UTCCory Boehne

Ok, so recommendations? No prob! :)

New Mexico Tech is an excellent choice, an in-person visit is really great, then you'll get to meet Virgil Lueth (State Mineralogist) who might be able to shed some excellent (FREE) light on the subject.

Then a short walk to the New Mexico Bureau of Geology & Mineral Resources will bring you to the office of Nelia Dunbar, she is also very nice, and can perform an electron microprobe analysis, with a backscatter, for about ~$125 or so. This will give you major chem elements, and has some trace capability, but more importantly, it will show xtal growth and has extremely good resolution (if working on small sample areas), however, be aware that you must prep the specimen to fit into a 1" circle.

Otherwise, you could check with Mountain States Research and Development, they have a very nice lab, but it is primarily geared towards mining and prospecting analysis.

21st Jul 2009 05:36 UTCAli Reza Eslami

can you introduce what is analyze and types of rock analyze?

21st Jul 2009 17:00 UTCDonald Vaughn

Ali Reza Eslami, to analyze is the scientific process of determining the chemical makeup of a substance and can be quantitative which gives a percentage of the the whole sample that the individual constituents makeup. whereas qualitative analysis just tells you what is present and not the amounts. Analysis can be performed either through chemical methods such as Assaying, or through analytic devices such as Xray diffraction spectroscopes.

any type of rock can be analyzed some substances are harder to determine through ordinary means of analysis

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