Mineralogy

Mineralogy

  • James Murowchick added an answer:
    Where can you buy synthetic quartz fluid inclusions?

    Where can buy synthetic quartz fluid inclusions produced using a solution of known composition? Especially in North America region. I want to use them as external standards for quantitative analysis elements in individual fluid inclusion by LA-ICP-MS.

    Thank you very much.

    James Murowchick · University of Missouri - Kansas City

    Contact Dr. Robert  J Bodnar at Virginia Tech.  He was involved with developing a method for making synthetic FIs and would know where to get some.

  • Zenaide C. G. Silva added an answer:
    What mineral is this?

    In my microscopic investigations on an andesite, I find a rather frequent mineral (please see the attached image), scattered as hypidiomorphic grains (size: 1 to >50 micrometer) with the following general composition (measured by SEM/EDS):

    Fe: 20 to 37%,

    Cr: 9 to 12%,

    O: 29 to 48%,

    Al: 4.5 to 12.5% 

    + variable amounts of Ti, Mg, Zn, Si, Ca

    I can not figure out a name for the mineral (although have already checked webmineral.com).

    I would be grateful for any help in this regard.

    Zenaide C. G. Silva · New University of Lisbon

    I am in agreement with those opinions: Fe-Cr spinel.

    Best regards, ZCS

  • Christopher. P. Brough added an answer:
    What mineral was exsolving from this chromite grain and where has it gone?

    Chromite grains have been observed with exsolution patterns before, including the fascinating example of clinopyroxene and coesite from the Luobosa ophiolite (Yamamoto et al., 2009) and earlier than that the umixing of different spinels from metamorphosed chromite in the Red Lodge district, Montana (Loferski & Lipin, 1983). However, in this case the exsolved phase is no longer observed and in nearly every case there is a distinct chloritic halo. So, the question is (i) what was the exsolving phase? and, (ii) why is there currently only chlorite to be observed associated with these exsolved chromite grains?

    Christopher. P. Brough · SRK Consulting

    Thanks Guenter and Harold,

    Yes, I reckon the exsolution phase must be amenable to the fluid phase and easily transferable under metasomatic exchange. Actually, one next step might be to analyse the chlorite in detail - to determine whether it is kammererite, clinochlore, chamosite etc... and whether that gives any pointers). To expand a little on the tectonic setting. I have seen this texture in two separate settings both of which are in ophiolitic chromitites.

    For the first setting (Turkey) this texture is abundantly present within the slightly more disseminated chromite lithologies but nevertheless present in both massive and disseminated chromitite. There is petrographic evidence for amphibolite facies metamorphism with the growth of other minerals such as cummingtonite and anthophyllite in the host rocks. 

    For the second setting (UK) this texture was only observed once, in one chromite pod. The ophiolite itself has not been regionally metamorphosed to amphibolite facies metamorphism but a recent paper argued that this chromitite locality in question (with the observed texture) had been to amphibolite facies metamorphism owing to close proximity to the basal thrust. They weren't interested in the texture (and I think they didn't observe it) but were deducing the metamorphic facies for other reasons. Nevertheless, it seems and interesting correlation between the two locations. 

  • Gert Nolze added an answer:
    Does anybody exactly know how the indexing of EBSD patterns works?

    The indexing of EBSD patterns is a quite secret business. It is clear that the band detection is done by Hough or Radon transform. It is known that the indexing uses the angles between planes described by the extracted bands. It is somehow known as well that these angles are compared with a table of theoretically determined angles using the lattice parameters of the phase. It is also published how the voting scheme of TSL works, but how the indexing really works is nowhere described (as far as I know). Does it has been published somewhere, or does anybody knows it more precisely? 

    Gert Nolze · Bundesanstalt für Materialforschung und -prüfung

    Hi Stuart, just now I could finally look through the literature you recommended and more than general and quite obvious equations (cross product) for the determination of plane normals derived from band positions I could not find.  What I am missing is anything about the derivation of the normals from the Hough peak positions (rho,theta), which are the extracted information about the band positions, but also any detailed algorithms, how the indexing based on the correctly described plane normals really works, i.e. how the software finally matches the theoretical look-up-table angles with the experimental angles in order to identify one possible orientation. The evaluation of all solutions using the confidence index is clear. 

    Specifically, what I am looking for is, how I can determine an orientation by a set of (rho,theta) values, i.e. how the planes or their normal vectors can be derived. In the referred publications a band (line) is only described by two points P and Q but actually you do not have these points but only rho and theta so that there must be another description for the determination of the normal vectors n. 

    @ Rohan: The second paper only describes, how to determine the bands but does not tell anything about possible indexing algorithm. Nevertheless, many thanks. 

  • Aidan Karley added an answer:
    Why does Serpentine viewed under polarized light exhibit colorful pictures?

    Dear Researchers,

    Would you please guide me:

    1- Why does Serpentine viewed under polarized light exhibit colorful images?

    Regards,

    Aidan Karley · Many major and independent oil companies

    Thanks for the replies too. It's a long time since I had to look down a petrological microscope, but even so I learned some things to be aware of if I ever have to use one again (which is unlikely).

  • Jeffrey de Fourestier added an answer:
    Is there any data out there on the iodine content in sylvite?
    There is data for Br in sylvite but I haven't found any on iodine in sylvite.
    Jeffrey de Fourestier · Carleton University

    The book "Marine Evaporites" by Frederick H. Stewart (1963) covers impurities in sylvite including iodine. He points out that the relative size of the I ion compared to Cl makes substitution difficult. On p. Y37 he gives an average of 0.014 ppm. But he also gives a brief discussion on Iodine in sylvite based on an analysis of 7 samples as well as giving a number of further references.

  • Jurgen Schnellrath added an answer:
    Would you recommend the M4 Tornado from Bruker or the Orbis PC from EDAX?
    We are going to buy a micro-XRF. Considering only the top models (SDD, polycapillary optics), which one is the best? M4 Tornado from Bruker or Orbis PC from EDAX?
    Jurgen Schnellrath · Centro de Tecnologia Mineral

    Schwerpunkt Goldgehalt an Schmuck, aber auch Identifizierung von sehr kleinen Edelsteinen, gefasst oder auch nicht. Einschlüsse, die sich an der Oberfläche befinden und grösser als 25 um sind, können damit auch identifiziert werden.

  • Paul C. Lyons added an answer:
    What is (are) the cause (causes) of the colors of minerals in incident (non-polarized) light?

    Geologists know that minerals come in a variety of colors and even the same mineral can have different colors.  What are the causes of this physical property?

    One must consider too that the colors of minerals may change due to radiation, heating, and degree of fracturing.

    Paul C. Lyons · United States Geological Survey

    Dear Emmanuelle, Thank you for the examles of minerals coating other minerals. 

    Mineralogy is an interesting subjectg, isn't it. Best wishes, Paul Lyons.

  • Gert Nolze added an answer:
    Who determined lattice parameters using HOLZ rings in EBSD patterns?

    As far as I know, two groups spend some time to investigate and determine lattice parameters in EBSD patterns using HOLZ rings. The first is the group around J.R. Michael from Sandia Lab. (USA) who developed this technique, and the second were E. Langer and S. Daebritz (TU Dresden, Germany). As far as I remember, Noran even sold a commercial system around 10 years ago based on the Michaels code, however I never read anything about an application. Is there any reason known why it is not applicable? 

    Gert Nolze · Bundesanstalt für Materialforschung und -prüfung

    Yes, but I must admit that their argumentation is quite questionable. Our current believe is that HOLZ rings are visible if structures are quite perfect and not the opposite. So their conclusion is more speculative... especially becuase they do not have any pattern simulation. Nevertheless many thanks, Volker.

  • Akram Mirlohi added an answer:
    Is it possible to differentiate Ortho- and Para-amphibolites based on geochemistry?
    We have amphibolites which clearly show sedimentary structures like bedding planes and are associated conformably with other sediments like greywackes, banded iron formations, dolomitic limestones and impure quartzites. Also, they consist of detrital quartz grains.
    The amphibolites mainly consist of tabular and prismatic hornblende and sub-rounded to well-rounded quartz set in a meager fine grained matrix of quartz, chlorite and sericite. But they have negligible felspars and when plotted in chemical classification diagram they fall into ortho-(igneous) amphibolite category. So is there any way for classifying the aphibolites into Ortho (igneous) and Para (sedimentary) amphibolites.
    Akram Mirlohi · University of Isfahan

    I have a question

    What is the differences between amphibole schist and para-amphibolite in amphibolite metamorphic facies?

  • Harald G. Dill added an answer:
    Has anyone ever seen such the attached sample? If yes, what is it any identification?

    I got this sample from a floor of carbonate/ limestone quarry but can not identify the elongated tools on the surface of the sample as I am not paleontologist nor sedimentologist any help of identification.

    Harald G. Dill · Leibniz Universität Hannover

    Dear Dr. Ferre,

    I  agree with you. It is why I always tried to get the classical paper from, e.g., Seilacher as an aid for interpretation in this discussion. I saw them several times in tidal and near-shore marine calcareous sediments, also the Middle East.

    Best regards
    Harald G. Dill

  • Matthias Halisch added an answer:
    Can anyone help to provide some geological / mineralogocal / petrophysical information about the reservoir carbonates as listed below?

    Dear all,

    We are currently working on a carbonate / petrophysical related project. For this, we got different carbonate sample sets from our project partner - unfortunately, without any information about their origin, depositorial environment, geology, mineralogy, etc.

    A google search was quite unsuccessful, so we hope, to find a little "shortcut" here. If anybody has some experience with these reservoirs, any information / paper / abstract provided will help!

    Thanks a lot in advance!

    Here the reservoir carbonates, for whom we need information as mentioned:

    - Leuders Carbonate

    - Edwards Brown Carbonate

    - Rocheron Carbonate

    - Indiana Limestone

    - Silurian Dolomite

    (all of these rocks can be found / bought at the companies link attached - unfortunately, they don't have any information or at least do not give them away)

    Matthias Halisch · Leibniz-Institut für Angewandte Geophysik

    @ S.L. Reeder: may I kindly remind you about the information yoe mentioned? You also might send them directly via email: matthias.halisch[at]liag-hannover.de

    Thanks!

  • Nenad Buzjak added an answer:
    Is there an updated list of cave minerals?
    Is there an updated list of cave minerals in the world? According to the excellent book Cave Minerals of the World by Carol Hill and Paolo Forti (1997) there was 255 minerals found in caves. Do you maybe know the number today?
    Nenad Buzjak · University of Zagreb

    Thank you Paul!

  • Harald G. Dill added an answer:
    Under what conditions can Hematite laths (lamellar hematite) in bornite occur?

    Under what conditions can iron-oxide laths (in some cases as box-work texture) form in bornite?

    Please see the attached picture.

    Harald G. Dill · Leibniz Universität Hannover

    Dear Dr. Nezafati,
    Dear Colleagues,
    I agree with the request of some more photographs on this matter but I am also realistic. Even if we have more images on a microscopic scale, a full-blown picture of the succession of minerals can only be provided in a reliable way as we integrate the field observations, which are with yours. If you claim another stage of mineralization under oxidizing conditions conducive to another generation of hematite, I can live with. There are e.g., vein-type deposits that start off with oxidic minerals go through reducing stages and end up eventually in another oxidizing regime. This is not anything out of the ordinary and has again and again been written in textbooks on ore mineralogy. Uplift, hydraulic conditions etc. are fluctuating very much in ore deposits.
    I think you got a lot of good information, but too much of a remote-controlled diagnosis might at the very end only put you on the wrong scent. There is only one who knows all about this deposit. The person who works from the pit to the publication on that site. Sorry for my very personal opinion on this matter.
    Good luck !
    Harald G. Dill

  • R. D. Ash added an answer:
    Who can recommend a set of standards for Fe-meteorite analysis?

    Dear all,

    I need to do some analysis of polished sections of Fe-meteorites by pXRF. As there is a bunch of certified standard steel materials, I wonder if someone can recommend a suitable set of these to build a calibration curve that works well on Fe-meteorites.

    thx, Florian

    R. D. Ash · University of Maryland, College Park

    We use several different standards and reference materials for the analysis of iron meteorites by LA-ICP-MS.  We have two steels from NIST, SRM1263a and SRM1158, which have both good and bad points (1158 has a lot of irrelevant elements for Fe meteorite analysis and 1263a has some heterogeneities in Nb, Ta and N [so not elements to worry about for Fe meteorites]).  John Wasson uses NBS809b as a standard, but this is now near impossible to find. 

    We also use iron meteorites as reference materials (NB not really standards).  Ataxites are generally pretty uniform in their composition and Hoba is widely used as a reference.  However many irons are depleted in volatile elements and so it is not practical to use this for Au, Ge, Ga standardisation.  We also use the meteorite Filomena as a reference, though this has issues with Cr.  We also have a couple of other meteorite samples that work well for us and we are confident that we know the composition of the pieces that we have and that they are uniform.

    I would echo Jerry's concern about the area which you are sampling - you need to ensure that you are getting something representative of the whole meteorite or you will get a misleading answer.


    Richard Ash

  • Matthias Halisch added an answer:
    Any suggestions for reservoir sandstones with different (dominant !) pore throat size for MICP-experiments?

    For a systematic MICP (mercury injection capillary pressure) experiment, we need some reservoir sandstones, that differ widely, concerning their dominant pore throat radius. This means, that we need on the one hand a sandstone that shows dominatly narrow pore throats, one that shows dominantly large pore throats and several in between.

    Sandstones need to be "clean", i.e. the amount of clay or other mineral phases affecting pore system should be as low as possible.

    I would like to use the classical Berea type sandstone for the "large" dominant pore throat faction, just to give you an impression.

    We would be grateful for any suggestions of sandstones, with smaller and even very small pore throats for our experiment. Sandstone name, dominant (mean) pore throat radius and purchase possibilities are highly appreciated! Of course, if you directly have some samples that fit, please contact me if you would like to "sponsor" some of them :)

    Thanks in advance!

    Matthias Halisch · Leibniz-Institut für Angewandte Geophysik

    Dear Peter, thanks a lot, in fact, we have plenty of Bentheimer on our own. The more narrow dominated pore system sandstones are needed ;)

  • Christopher. P. Brough added an answer:
    How does aragonitic limescale form inside the boiler system of vending machines?

    Vending machines, operating at a water temperature of 95oC and atmospheric pressure usually form calcitic limescale. This is the trade off to having coffee that tastes somewhat decent and means that standard vending machines need to be cleaned every 6 months or so. Rarely though the limescale that forms is aragonitic (which isn't stable at the temperatures and pressures present in a vending machine). My question is, why is the aragonite forming in conditions for which it is not stable?

    Christopher. P. Brough · SRK Consulting

    Thanks Vincent, that is certainly highly suggestive of a water-chemical control - unless you are very unlucky in your kettle manufacturer! Romani, I think the ion exchange could still work as in theory you wouldn't seek to exchange out the Ca. The chemical control would presumably be excessive Mg or Sr or some other cation whose ratio with Ca leads to the stabilisation of aragonite. As such you would probably start by exchanging out the heavy ions first and exchanging in more Ca.

  • Harald G. Dill added an answer:
    Is there any data / paper available concerning a sandstone called "Idaho Gray"?

    I do need some more information on a sandstone called "Idaho Gray" (link where it was bought attached), especially related to geological setting, formation, depository. If available, also concerning petrophysical investigations.

    Thanks for any tipps & hints!

    Harald G. Dill · Leibniz Universität Hannover

    Dear Colleagues,

    "Idaho Gray" seems to be a trademark similar to "Deutsch Rot" (German Red = Upper Devonian hematized flasered sparry limestone). I have used some of them used in my "Chessboard classification scheme of mineral deposits". Most of the rock slaps I got from the "Deutsches Naturstein-Archiv" it is a state-run institute at Wunsiedel with approx. 6000 specimens across the globe in its archive. You may find there an image, mineral composition etc. If the decoration stone or ornamental stone is used across the USA I can image you will find at the DNSA some information.

    Best regards
    Harald G. Dill

  • S. Curtze added an answer:
    Why samples are not always tilted in TKD (Transmission Kikuchi Diffraction) mode, but sometimes slightly tilted against the EBSD screen?

    Is there any proof that the tilt improves the signal, or does it only affects the pattern center positioning since the working distance can be increased so that the gnomonic distortion are not that dramatic? If they are, the band detection is not that precise so that the orientation determination is less accurate.

    S. Curtze · NACON - nanoANALYSIS CONSULTING OY

    Well, that's basically what I meant by energy filter, i.e., the high energy electrons responsible for the formation of the pattern visible on the phosphorscreen have a shorter path length. I'm looking forward to see your results once they'll be published.

  • Piotr Gunia added an answer:
    Is it possible to obtain bulk Raman Spectra for the traverse of a 2 cm rock chip?
    How complicated can the procedure be? We aim to map serpentinite mineralogy on a regional scale and are trying to find method for quick and reliable identification of serpentine polymorphs in a rock chip. It has been demonstrated that Raman spectroscopy allows one to distinguish between antigorite, chrysotile and lizardite. Does Raman spectroscopy provide an opportunity to get bulk scan spectra e.g. for 2 cm traverse in a rock chip? We need to be able to then pick signatures of different serpentine polymorphs from bulk spectra and by that see which phases are present.
    Piotr Gunia · University of Wroclaw

    It is possible. You can  to use a traverse in a small distance. The most valuable equipment  for these Raman spectra studies is Lumos apparatus produced by Bruker in Germany.

  • Can wind transport produce a mineralogical selection on volcanic tuffs deposits?

    Can wind and/or water (marine environment) transport produce a mineralogical selection on volcanic tuffs deposits? Do you know any example?

    Emilio Evo Magro Correa Urbano · Universidade de Trás-os-Montes e Alto Douro

    Thanks a lot Mr Dill, your answer will definitely help me.
    Best regards, Emilio

  • Marlina Elburg added an answer:
    What process can make olivine Fo lower than the equilibrate with melt?

    Whole rock Mg number lies between 0.70-0.75, but the Fo of olivine is 0.75-0.85. According to  Roeder and Emslie,1970, the caculated Kd is between 0.42~0.46. So what process makes this kind of condition? The contents of Ol phenocryst is less than 8%. I am very confused; did the Ol assimilate by crust? Why didn't the melt?

    Thank you very much

    Marlina Elburg · University of Johannesburg

    One possibility is that the olivine is simply not in equilibrium with the melt, and that you have an example of magma mixing. In some case you can see reverse zoning in the olivine, or resorbed edges to the olivine. Another possibility is that your whole rock composition is not a reflection of the liquid composition (but then you would need to have a siginficant amount of other phenocrysts present, such as cpx).

    I assume that you calculated the Mg-number of your whole rock based on the total Fe-content? If so, then it could be that there is a significant fraction of the iron present as Fe3+, thereby decreasing the 'true' Mg# ( Mg/(Mg+Fe2+)) of the magma. 

  • Michael R. Carroll added an answer:
    Please can you suggest a concise and precise text/journal paper which will tell me about zeolites?

    The text should tell me about its structures, types and applications

    Michael R. Carroll · University of Camerino

    you can try Mineralogical society of America, Reviews in mineralogy series of books

    see http://www.minsocam.org/

    Mineralogy and Geology of Natural Zeolites, Reviews in Mineralogy,  v. 4

    Naturnal Zeolites: Occurrence, Properties, Applications, Reviews in Mineralogy and Geochemistry, v. 45

    Mineralogy of Clay and Zeolite Dusts (Exclusive of 1:1 Layer Silicates).
    David L. Bish and George D. Guthrie, Jr. (1993)
    Health Effects of Mineral Dusts, Reviews in Mineralogy, 28, Chapter 4

    Silica Zeolites and Clathrasils.
    John B. Higgins (1994)
    Silica: Physical Behavior, Geochemistry and Materials Applications, Reviews in Mineralogy, 29, Chapter 15

  • Marlina Elburg added an answer:
    Does anybody know of glazed xenoliths from volcanic regions other than the Eifel (in Germany)?

    These stones have a natural (!) shiny glaze (see pic) which may be colored or not. I would like to know if there are other occurrences worldwide. May be a museum houses some samples somewhere in the world?

    Marlina Elburg · University of Johannesburg

    Very nice, and thanks for the information on the variable colours in a single location. That does indeed show that the xenolith, not the magma, is the cause of the colour. I now know what to hunt for next time I am standing on a volcano!

  • Alessandro Genovese added an answer:
    Can any suggest a simple way or technique to calculate the oxygen stoichiometry in ABO3 perovskite

    I just want to know the 'd ' value in ABO3-d

    Alessandro Genovese · Italian Institute of Technology (IIT)

    Another way to determine the Oxigen could be the Wavelength-Dispersive X-Ray Spectroscopy (WDS) that allows to discriminate the element stoichiometry of materials.

  • Caitlin E. Hicks Pries added an answer:
    How does mineral surface area affect soil organic matter and 14C at depths?

    Mineralogy is known to have some impact on residence time and stock of soil organic matter. How mineral surface area affects soil organic matter and 14C at depths in various vegetation types, e.g., grassland, tropics?

    Caitlin E. Hicks Pries · Lawrence Berkeley National Laboratory

    That is generally true for layered clays--a 2:1 layered clay has more surface area and generally more reactive sites than a 1:1 clay. It can also be about the types of minerals and the amount of potential reactive sites they have. For instance, amorphous minerals generally hold more OC than similar minerals with a more crystalline structure. Margaret has a good paper in Nature about this (1997). I would also look at papers by Katherine Heckman. In terms of with depth, many studies have found that a higher percentage of OC is mineral-associated at depth based on the amount of OC released when the samples are demineralized (look at papers from the early to mid 2000's from Cornelia Rumpel's lab).

  • Haoyang Zhou added an answer:
    Is there any case that gold is hosted by magnetite directly?

    Why is gold associated with sulfide minerals?Is there any case that gold is hosted by magnetite directly?

    Haoyang Zhou · Sun Yat-Sen University

    Thanks alot, Ali. Would you please provide more detail about that deposit or relevant references?  

  • Gavril Săbău added an answer:
    Why are A-O bond 40% greater than B-O bond in Perovskite structure ?

    I am finding it difficult to find the bond length of A-O and B-O bond in Perovskite?

    Gavril Săbău · Geological Institute of Romania

    Because of the cation sizes; the A position is assumed by cations having larger radii like Ca2+ (100 pm), Sr2+ (118 pm), while the B position is occupied by Ti4+ (60.5 pm, that is about 40% smaller) or similar cations, all coordinated by O.

  • Uriah Alexander Lar added an answer:
    How would one attribute the reactional rim around the olivine crystal in the photomicrographs here attached to?

    Attached are photomcrographs (under PPL and XPL) of olivine phenocryst in a basalt rock. Can we say that the reactional rim is as a result of rapid cooling/recrystallization? How?

    Uriah Alexander Lar · University of Jos

    Dr Evans, I appreciate the article on serpentinization in ol-troctolite. Quite revealing.

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