Mineralogy

Mineralogy

  • Sylejman Hyseni added an answer:
    Can we see Fe2O3 in Sillimanite?

    Is it possible to have Fe2O3 in Sillimanite?   I observed (under SEI) a sillimanite looking grain (in a metamorphic rock sample)  with characteristic cross fractures in my SEM-EDS studies. But several points along the very same grain show the following composition;

    Alumina - 58 - 61 wt%

    Silica - 35-38 wt%

    FeO+Fe2O3 - 3 -5 wt%

    Is this gain is sillimanite or something else. Is it possible Alumina to be replaced with Fe2O3?

    Thanks in Advance!

    Sylejman Hyseni · University of Prishtina

    Is it possible to have Fe2O3 in Sillimanite yes (because we have replace Al+3 and Fe+3.

  • du Peixin added an answer:
    How can I prepare a good sample for AFM analysis, or where can get the mica of good quality?

    i want to perform AFM on the spherical sample with a diameter about 3nm, but the mica used for sample preparation in my lab is of poor quality, i cannot make sure what i see is the sample or background, can anyone who can tell me how to prepare a good sample for AFM analysis, or tell me where can get the mica of good quality?

    du Peixin · Chinese Academy of Sciences

    thank you, Edward Kramkowski ,all the best

  • Valentina Batanova added an answer:
    Cr in augites - are there any clues about the processes evolved in the composition?

    I'm studying augitic pyroxenes from a back arc volcano, included in basalts. Till now I find all those pyroxenes quite similar in terms of major elements, but different sized crystals and along one crystal (from core to rim) the composition in minor elements (such as Ti, Al and Cr) vary significantly, being Cr the one varying from 0.1 to 1.2%. 

    I find Ti and Al (and also Na) with fitting profiles, but Cr seems not to be related with all the rest. Does anyone have a clue processes leading Cr partitioning? fOmay be an candidate but I'm not sure ti may be the main reason.

    Valentina Batanova · University Joseph Fourier - Grenoble 1

    Hi,

    Phenocrysts of Cpx usually have high Cr content. Cr content of CPX depend also from pressure, looks the publications of Paolo Nimis for example.

    Regards

  • Aurelio Sanz added an answer:
    What information is required to verify a new mineral identification?

    During some routine pegmatite mineralogy we came across an unknown mineral in association with the very rare-mineral 'fluorcalciomicrolite'. We no longer have the grab sample from which the thin section was taken but still have the thin section and have had the opportunity to analyse it quantitatively, along with some element mapping.

    The results confirm that our mineral is possibly unique or possibly a second world occurrence of the recently discovered 'peterandresenite' but with high concentrations of Ta, presumably substituting for the Nb. The question is, what additional work can be done to confirm or publish the results bearing in mind all that we have is a normal 30 micron thin section of the mineral in question? 

  • Gary Michelfelder added an answer:
    Is it possible to resolve single crystal XRD data for naturally twinned and zoned garnets?

    I have a student working on natural garnets that show a unique crystal habit and cleavage.  We analyzed two of these garnets by single crystal XRD thinking that we may have a structural defect that may be affecting the cleavage planes.  We selected two crystals that when imaged by BSE the garnets showed no signs of compositional zoning or twinning, but when we analyzed them by XRD the data can not be resolved without the addition of zones and twins.  Is there a program or statistical method that we can use to resolve whether we have zoning or twinning in the samples?  Or it there a different method that could be used to resolve this information?  

    Gary Michelfelder · Missouri State University

    Ravi and Daniel-

    Thank you both for your responses.  I am sorry about the delayed response, I have been in the field for the past couple weeks.  Ravi- I am interested in the 2D Bragg XRD.  We have sample sizes that range from 0.3 mm to softball size with an average size of 2-3 cm in diameter.  The 0.3 mm samples are the samples we ran by XRD that showed the twinning.  Our XRD is not capable of analyzing anything larger so I don't know if the larger samples show twinning as well.  In addition to the variation in sample size we also have samples that are gem quality that we have not been able to analyze due to there size. I will only be in the office until Tuesday next week and will be heading back to the field with a couple graduate students until the beginning of July, but I will try to send some post some of the data. 

  • Hassan Shirazi added an answer:
    What is the maximum lattice parameter accuracy of EBSD patterns?

    EBSD patterns are usually assumed to have a quite low accuracy regarding the lattice parameter determination. What are the typical limits and which parameters are important? Up to which resolution (or binning) the acquisition of patterns make sense? Are there papers published about this topic?

    Hassan Shirazi · University of Tehran

    as you mentioned EBSP is defined by the lattice parameters describes the maximum intensity gradient at the margins of the Kikuchi bands width in an EBSP. I am agree with 5% by taking account the resolution of detector.

  • Marlina Elburg added an answer:
    Where can I find scanning calorimetric data from pure crystalline quartz up to temperatures greater than 1050 C?

    Most calorimetric data appears to be confined to lower temperatures somewhere a little in excess of the alpha to beta transition but I can't find higher temperature data. 

    Marlina Elburg · University of Johannesburg

    You're quite right, and I was indeed vaguely wondering whether you were talking about disequilibrium processes - or that you simply missed the existence of tridymite (I have clearly been doing too much undergraduate teaching that I entertained this option). So your question is a good one, to which I unfortunately do not know the answer!

  • Thomas Oberthür added an answer:
    How can I identify heavy Ti minerals like ilmenite & rutile from other heavy minerals like magnetite in a beach placer?
    Can these Ti minerals be identified by an ordinary microscope?
    Thomas Oberthür · Bundesanstalt für Geowissenschaften und Rohstoffe

    Easiest way - take a magnet.

    Thomas

  • Willem Kruger added an answer:
    What is the effect of solid solution in minerals on their partition coefficients?

    If I understand correctly, partition coefficients (concentration in solid / concentration in melt) are usually determined according to the weight percentage of the material involved. However, the density of a mineral can vary depending on the elements present. For example, iron-rich olivine (fayalite) is much denser than magnesium-rich olivine (forsterite). If the partition coefficient is calculated for, say, nickel for the olivine solid solution series, wouldn't it have a lower partition coefficient for fayalite than it would have for forsterite that contains the same amount of nickel because iron is heavier than magnesium? (In the same manner than fayalite contains less silica than forsterite on a weight basis). I'm curious because the literature I've read only report one partition coefficients for olivine, while I feel that the values will vary depending on the Mg/Fe ratio.

    Any help would be appreciated.

    Willem Kruger · North West University South Africa

    Thanks a lot everyone, especially for the article Max! I'll take a look at it.

  • Sundarrajan Marimuthu added an answer:
    Dear researchers, is there any handbook of rock mineralogy data of IR absorption?

    Rocks are composed of various minerals and metals. Is there any handbook which comprise IR absorption data for rock minerals?

    Sundarrajan Marimuthu · Sri Chandrasekharendra Saraswathi Viswa Mahavidyalaya University

    Thanks a lot professor. I will come on further climbs.

  • Dolores van der Kolk added an answer:
    Have you seen anything concerning Mesozoic pre-Valanginian glendonite occurrences in Arctic Canada and Alaska?

    Jurassic deposits of the Siberia and NE Russia are characterized by numerous glendonite occurences, especially widely distributed in Upper Pliensbachian and Bajocian-Bathonian. Did anybody know any information about the coeval glendonite occurrences in Northern America? I know only two briefly mentioned records of "stellate nodules" in the Kimmeridgian of Northern Yukon and Mid Volgian of Prince Patrick Island 

  • V. Divakara Rao added an answer:
    What is the textural significance of the photomicrograph attached?

    On behalf of my lab-mate Soumi Chatterjee:

    We are working on an alkali basalt sample, where we have documented some of this flower like aggregates of tiny euhedral to subhedral clinopyroxenes with minor amount of spinel occurring within fine grained basaltic matrix. EPMA indicates that they are Ti-rich Diopside. It would be extremely helpful if anybody can give some clue on their origin, textural significance etc. Moreover, any literature references would be highly appreciated. Attaching the corresponding photomicrograph as a Pdf file (see the attachment)

    Fig Caption: Photomicrograph of the texture A) under Plane polarised light; B) under cross polars; C) Reflected light photograph; D) BSE image

    V. Divakara Rao · National Geophysical Research Institute

    the crystallization process in a magma pool,if takes place in undisturbed P-T conditions ,ie where there are no tectonic disturbances will have the assemblages as expected. But this type of  xenocrysts ,or partial retrograde assemblages in association with progressive crystallization  needs. a better understanding of the tectonic setup .

  • Mues Huang added an answer:
    Why are the twinning quartz not common in thin section?

    The twinning of some minerals are relatively common in hand species,
    but not observable in the thin section scale,
    (at least in the volcanic rocks),
    my first thought is that the structure of quartz make it this way,
    but the common twinning mineral, feldspar, are also tectosilicates,
    then I thought it was because quartz might be the phases that solidified last,
    making it have least space to growth in the magma,
    but I think this point is weak to explain this,
    does anyone know something about this?
    Thanks for helping in advance.

    Mues Huang · National Cheng Kung University

    Thank you all for answering!
     : )

  • Teresa Diaz Gonçalves added an answer:
    Does anyone know where to find values of the compressive strength and Young´s modulus for halite, thenardite and nitronatrite?

    I've searched thoroughly in internet resources and mineralogy handbooks, but it does not seem easy.

    Thank you in advance!

    Teresa Diaz Gonçalves · National Laboratory for Civil Engineering

    Hello! I found of values for the elastic constants of one type of crystal in an earlier version of the Handbook of Physical Constants. For the other two types I eventually could locate reliable experimental values from a search that started on Landolt Bornstein database (to which I don't have access). Thank you both!

  • Kenneth M Towe added an answer:
    What types of organic polymers made or found on Earth have affinities to those found in insoluble organic residues from carbonaceous meteorites?

    Insoluble organic matter residues are the remaining insoluble organic material after extreme acid digestion of the extraterrestrial material. They contain complex morphologies that exist as either: isolated spherical compounded shapes; hollow spherical objects or irregular (non spherical) shapes which internally often contain the same conglomeration of spherical features. Please see attached DF STEM images of some of these morphologies from two organic rich carbonaceous chondrites. As the residues are a product of the removal of surrounding mineralogy (i.e. context in situ is lost), connected features on the submicron to micron scale in the images, by approximation, should only be considered. Thanks!   

  • Terance Virtue added an answer:
    Is it possible to use ditch cuttings for mineralogical investigations when one has no access to core samples?

    the research is on ironstone deposits but core samples are not available to us, can drilled cuttings be used for such investigation? if yes, which procedure would be the best for preparing the samples for trace element REE and isotopic analysis and which analytical technique will give the best result?

    Terance Virtue · Signal Equities, LLC

    It is not hopeless but you will have to be carefull to separate cuttings that are not from the lag depth and may be from shallow formations previously drilled. Also, there could be some winnowing effect as a result of particle shape, density and grain size. Lighter and or smaller particles may have a tendency to remain entrained in the drilling mud and may be recirculated. Larger and denser particles may tend to sink when circulation stops during a drill pipe connection.

  • Tom Jäpel added an answer:
    Radiation damages during EBSD investigation in SiO2 (agate)?

    Did anybody investigated agate and observed radiation damages caused by electrons?

    Attached is one image which displays a forescattered elevtron image. It displays clearly orientation contrast in quartz (big grains) as well as in the fine-grained agate. If I try to scan the agate in EBSD mode, (dwell time in the scale of 20-30ms) the structure obviously collapse the the electron beam interaction. A strong topography change appears always there where agate is assumed. A reduction to 10keV electrons does not help.

    A similar effect I observed at small-grained calcite at a contact zone. Patterns are locally detectable, but only once. Then a clear topography change become visible comparable to agate. Investigating calcite in bigger grain (highly twinned and a few 100µm away) this effect does not appear at all.

    Tom Jäpel · Elektronen Optik Service Dortmund

    Hey Gert,

    your FSD image looks more like charging than phyiscal surface modification from my humble experience. Did you try this EBSD scan with low vacuum like >5 Pa Nitrogen or so? If you don't have a device for that maybe I can do a scan for you? Just send me the sample.. you know where to find me :D

    cheers,

    Tom.

  • Dejan Prelevic added an answer:
    Does anyone know the software-Minpet? Under the circumstance of Windows 8.1, it can't run, how do you deal with this situation?

    Minpet——( a software for Mineralogical and Petrological data processing system), it can run under the Windows system XP or Windows 7. However, it can't run under the circumstance of Windows 8.1. 

    Does anyone have the lastest version?

    Please contact with me, thank you!

    My e-mail is xiegen@cugb.edu.cn.

    Dejan Prelevic · Johannes Gutenberg-Universität Mainz

    If you really insist to use Minpet, you might try with  VMlite workstation, which is an emulator for XP at windows 8. It works perfectly and uses a part of your resources, but just "economically". Alternatively, Igpet is usefull as well

  • Nirmalya Chatterjee added an answer:
    Can anyone identify this mineral?

    I came across really weird mineral in marble. It's somewhat metamorphosed: some amphiboles, chlorite, epidote biotite, plagioclase and potassium feldspar has formed. Its composition is (wt%): SiO2 51.5; Al2O3 25.36; CaO 14.14; K2O 0.46; Na2O 5.62; S 0.81, some Cl. Total is 97.89 wt%. It looks a lot like amphibole, but it's composition doesn't mach at all. I feel it's beyond my knowledge, or something that I didn't even consider to be. Thank you, in advance.

    Nirmalya Chatterjee · Indian Institute of Technology Bombay

    Most probably scapolite!

  • Govindasamy Usha added an answer:
    Is there any relation between formula unit (Z) and lattice parameters?

    I want to know more about Formula unit (Z) in crystallography.

    Looking for clear explanation.

    Govindasamy Usha · University of Madras

    Dear Aditi, in general we could derive the space group ,hence the number of molecules in the asymmetric unit from the relation between the lattice parameters, When space group changes, Z will also changes.

  • Sheng-Hong Yang added an answer:
    How to estimate Fe2+/Fe3+ ratios of clinopyroxene on the basis of an electron probe?
    The electron probe gives only the content of total iron shown as FeO. Now I need to calculate the partition coefficients of Fe2+/Mg2+ between cpx and host melt, but the Fe2+ of cpx is unknown. Then how to estimate it? Any suggestions or representative papers would be appreciated.
    Sheng-Hong Yang · University of Oulu

    Dear Lyde,

    Thanks very much for your suggestions. As in many cases, pyroxenes experienced variable degrees of alteration, which may change the Fe3+/Fe T. Maybe average of several grains is a better solution. And  it is also difficult to find standards with different composition, for which the Fe3+/FeT has been determined by other methods. So this may be why this method is not widely used up to now. 

    Another option is Mössbauer, this is also for powder samples, but alteration is still a problem which may change the composition. 

    Or XPS, maybe worth to have a try.

    Cheers,

    Shenghong

  • Huan Li added an answer:
    Is it still available to calculate the Nd model ages for granites when 147Sm/144Nd ratios are higher than 0.15?

    These mineralization-related granites have high 147Sm/144Nd ratios ranging from 0.1524 to 0.2914. I am appreciated if anyone can anser my qustion.

    Huan Li · China University of Geosciences

    Thank you all for your kind explanations!

  • Virendra Kumar Saxena added an answer:
    How are geothermometers based on the SiO2-quartz and SiO2-chalcedony reliables in bicarbonate Mg-Ca waters related to sand with a dolomite cement?

    For geothermal pourposes I am researching waters related to Cretaceous limestone-dolostomes and sandstones not too far of an inverse fault. The temperature at surface conditions is of 19 ºC (water for drill after 24 hours of pumping) that is quasi equal at the temperature estimated using the local geotherm, but I get a reservoir temperatura of 39 ºC using the silica-quart geothermomer. The Saturation index of quartz is oversaturated =0.35. 

    Virendra Kumar Saxena · National Geophysical Research Institute

     Javier, In your case Quartz silica geothermometer may not work. Better you use SiO2 Chacedony thermometer. However Na-K -Ca geo thermometer can also be tried. You have correctly evaluated  with good approach. Equilibrium of kaolinite with water may indicate < 100 degree centigrade as base temperature.

  • Morteza Einali added an answer:
    I would like to recognize these minerals based on laser raman spectroum?

    Dear Researchers

    I found two unknown minerals during my laser raman on fluid inclusions (halite-bearing inclusions) on porphyry copper deposits. These minerals are transparent. I checked by RRUFF database but I could not identify them. I attached their raman spectrum and background quartz. They analysed by Nd-YAG laser (532.2nm) and LABRAM-Jobin-Yvon system. Thanks in advance for your attention and help.

    Best Regards

    Morteza Einali · Shahid Beheshti University

    Dear Peter

    Ok! It was a format problem. I have attached the graph. Thanks a lot for your help.

    Regards

  • Dipak C Pal added an answer:
    What this Co-rich (approx 47-50 wt% Co) sulfide mineral is?

    We have a cobalt-rich sulfide mineral in an association of chalcopyrite + pyrrhotite + magnetite from a sulfide deposit. The phase has a higher reflectance than pyrrhotite and chalcopyrite and is anisotropic (somewhat similar to millerite!). The calculated formula (based on EPMA data is broadly Co(0.76-0.83)Ni(0.14-0.18)Fe(0.10-0.20)S and the Metal/Sulfur ratio varies between 1.11 to 1.15. The composition is similar to Cobalt pentlandite (cubic) reported from many deposits but the anisotropism is confusing! Does anyone have a clue what this mineral could be?  Links to relevant references would be highly appreciated.  

    Dipak C Pal · Jadavpur University

    Thanks Harry! We recognize that it is worth checking the mineral by XRD and reflectivity test. We have done EPMA. We also have Co-Mackinawite in these ores. To my understanding known Mackinawite does not contain so much of Co as this mineral in question contains. Please attach your paper.

  • Nilda E. Urbina added an answer:
    Could there exist a transition between intermediate sulfidation and low sulphidation epithermal deposits?

    Sillitoe and Hedenquist, 2003, indicate that  intermediate and low sulfidation epithermal deposits have been found to be mutually exclusive mainly in the tectonic setting of formation. However, we found deposits that exhibit composite characteristics of both IS and LS mineralization styles as the most epithermal deposits in Mexico (Camprubí A. and Albinson T., Depósitos epitermales en México: actualización de su conocimiento y reclasificación empírica. Boletín de la Sociedad Geológica Mexicana, Volumen Conmemorativo del Centenario, Revisión de Agunas Tiplogías de Depósitos Minerales de México. Tomo LVIII, N° 1, 2006, pp. 27-81).

    Nilda E. Urbina · Universidad Nacional de San Luis

    Dear Greg,

    I find both papers very interesting! Thank you very much for your time and for sharing your knowledge with me. I did the download of the latest paper and I think the Fig. 9 represents very well what you explain me in the text above. It is also very similar to what occurs in the deposits studied by us. Now, when you say "Earlier Leach and Corbett classification" refers to Special Publication 6 of Society of Economic Geologist (1998)? (I have it). Also, I know some of your other works as epithermal Gold for Explorationists (2002), or that from the Ishihara Symposium (2003), etc.

    Anyway, this exchange is helpful and enlightening for me, mainly because I didn´t have these files you sent me. Thank you very much!

    Nilda

  • Harald G. Dill added an answer:
    How can I identify arfvedsonite in thin section?

    I have the following thin section of alkali feldspar granite. Are blue minerals arfvedsonite?

    Harald G. Dill · Leibniz Universität Hannover - Institut of Mineralogy

    Dear Mr. Athari,
    the new set of thin sections shows two very nice examples on the relationship between mineralization and kinematic processes, with pressure shadows and quartz precipitation. In my opinion the discussion moves gradually away from the granite as the "father of everything" and according to what I have seen structural processes, including mylonitization and Fe mineralization become more and more centerpiece in the discussion. I hesitate to spark a new round of discussion on the basis of the newly introduced thin sections. Prof. Bonin´s remark as to the scale seems to me a keystone issue. You have to go through the issue form the macro through the micro scale and the position of the various lithologies relative to each other is another factor which we cannot talk about.
    This is in general a weak point of some questions raised in the RG´s Q & A processes. I do not try and blame the person who goes along with that  for his/her doing  because I know as a "young recruit in sciences" you try and catch every straw passing by.
    I think you did not only learn about Na amphibole s.s.s. but also how to take an approach and come to grips with an issue like that.
    I wish all the best and I welcomed the discussion you initiated and managed as an anchorman.
    H.G.Dill

  • Nouha Ben Messaoud added an answer:
    Have you ever heard or read before about synthesizing zeolithes starting from clay at normal (Non-Hydrothermal) conditions?

    I have always read about synthsizing zeolithes from clay or chemical starting materials in hydrothermal conditions. But I have never met a paper talking about zeolithes synthesis in "normal" conditions, below 100°C. Have you?

    Nouha Ben Messaoud · University of Carthage

    Thanks David. But it is again by "hydrothermal activation".... 

  • Jayabalan Manickam added an answer:
    Can any one provide thin section photographs of melilite bearing lamprophyre or alnoite?

    We had encountered a small dike with evident porphyritic texture in both hand specimen and thin section scales. The euhedral minerals are colorless, tabular or elongated tabular some times wedge to partly lozenge shaped , non pleochroic, poor cleavage, pale grey interference color and straight extinction. Most are twinned - simple or penetrative. Several are zoned with a straw yellow corona or rim (in XN condition). We suspect the euhedral mineral to be melilite. The groundmass is fine grained. 

    Jayabalan Manickam · Government Arts College (Autonomous), Salem 636007

    We also suspected the laths to be K feldspar,but it displays straight extinction. Some smaller laths and lozenge shaped grains display distinct reaction rims which stands out in XN condition. We are awaiting the results of the chemical analyses. Thank you for your response.

                                       M.Jayabalan.

  • Milad Saidian added an answer:
    Calculation of Individual mineral magnetic susceptibility using bulk mag sus and mineralogy data?

    Hi All

    I have bulk magnetic susceptibility (MS) for 30 rock samples. I also have detailed mineralogy data using XRD. Can I simply calculate the individual mineral susceptibilities by a minimization function?

    Is it right to say weighted (or volume) average of individual  susceptibilities is equal to bulk susceptibilities? What are the assumptions?

    Milad Saidian · Colorado School of Mines

    Dear Viktor,

    Thanks for your answer. As I mentioned in my answers to Mr. Dill I do not have minerlas with crazy high magnetic susceptibility. The highest are pyrite and chlorite. I will try to use a big sample set to increase the statistical accuracy of the minimization function.

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