- Mohammad Belal Hossen added an answer:30Is the declaration of the magnification in images still acceptable?
Also nowadays where everything will be zoomed during printing the magnification is given, although this does not match to the often also given scale bar. Is this still acceptable, or shouldn't one use magnifications anymore?
When the image were taken, a scale bar was given. If the image dimension changes the scale bar also changes. So the visible image acceptable with its scale bar.Following
- Ruediger Burkhard Richter added an answer:14How can we depress kaolinite clay to improve flotation gold recovery?
we have gold in pyrite ore, we extract this gold by flotation, but some time we have with our ore kaolinite clay which interfere with gold in flotation and give and give us bad gold recovery.
We as BAUER also have our own bio polymers available in our large group. If you have a real problem with your clay and you'll find a solution, for that you can contact me under firstname.lastname@example.org. My Competence Center is performing flotation lab-scale tests on a regular base and therefore we have plenty of practical experience and a certain practice to perform such things professional.
Ruediger Richter, Abu DhabiFollowing
- Mark I. Pownceby added an answer:6How can I identify ore minerals smaller than 5 microns in fine-grained uranium mineralization bonded to the Cenomanian sediments?
The study of ore mineralization is difficult for the size of mineral phases (in μm), gel nature of components etc. Application of traditional geological instruments (EPMA, SEM, XRD) is often limited due to the low-grade ore, particle size or colloidal nature of uranium and uranium-bearing phases.
Hello Petr, fine-grained mineralisation can indeed be a problem in characterising uranium ores. Many of the answers provided above regarding EPMA or SEM techniques are correct. Please see the attached document for issues regarding identification of fine-grained U-mineralisation via electron beam techniques.Following
- Sebastián Grande added an answer:18What's the groundmass of this volcanic rock?
I am running a round robin test on applied petrography and I am a bit lost on one sample, for which I do not have any precision concerning origin, chemistry etc. The aggregate is black so I thought "ok this is a basalt" but I do not see any lath of plagioclase (fortunately there is olivine). I suspect some tridymite/cristobalite, volcanic glass (devitrified?) but what about the prismatic crystals (high birefringence colors) which form almost all the groundmass ? Many thanks in advance.
Surely a rock with so many unsaturated minerals (olivine, leucite, analcime) will have a %SiO2 quite low, in the order of 44% or even less. But in the original question of Vincent Thiery there's no mention of any chemical analysis, only of a "round robin test" on petrography.Following
- Pragadeesh K Sekar added an answer:28Can someone help me interpret the XRD result of a rock mineral sample?
I have done XRD for the samples I had. I am using Highscore Plus software for indexing. I am finding difficulty in determining the phases in it. For instance, a selected compound in automatic match with standard, shows the highest(100%) relative intensity at 12.80 & second highest at 25.39. Actually peak at 25.39 is higher than that of 12.80. In this case, can i consider the presence of that compound or not. Like this, many other doubts are there, like whether counts affect relative intensity.
I expect your valuable critics for one(I have attached) of the results.
Thanks to everyone for helping me in gaining knowledge about the X-ray analysis as well as sample preparation and the critics on the results is very useful. Dr.Kenneth and Dr. Ravi played significant roles in this active discussion, whose participation in future discussions will be benefiting the community for sure.Following
- Mohammad Fadaeian added an answer:8How can I find out if the chalcedony is length-slow or length-fast?
I am studying fossils discovered in paleosoil deposits that are full of cavities refilled by chalcedony. I would like to check what type of chalcedony it is, since that can give you information on the depositional context. I have read about the structural difference between the two (e.g. in Heaney 1993, A proposed mechanism for the growth of chalcedony): the fibres crystallites have the c-axis perpendicular to the fibre axis in the length-fast chalcedony, and parallel in the length-slow chalcedony. But I don't know how to check that in practice... does anyone know a procedure for that ?
It's been a while since my last cristallography/mineralogy class...
I agree with the answer from James, But important goal is determined Chalcedony crystallographic axis a,b,c . however, you can provide thin section of Chalcedony in three trend and study in polarized microscope that have Universal stage and find c axis(length) of your sample.
help for you: http://www.geochemsoc.org/publications/geochemicalnews/gn140jul09/theuniversalstage/Following
- Longgang Fan added an answer:23Do you think these are fluid inclusions?
Do you think these bubbles are fluid inclusions? They have the same Raman Spectrum with the host crystal.
I also think Kris Piessens's answer is very good and the device stuff is very important. The reason I asked this question is almost based on my shortage of the experience for studying the fluid inclusions. As a green hand, the "little accident" really hit my fragile confidence. So I came here for advice, and my question should have been "How to identify the fluid inclusions? " All the answers really inspired me a lot.
- Abdulkareem Toyin added an answer:9Is 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?
You can make use of any available samples,either dicth or core but what matters is knowing the age range of your various samples if you are doing correlation. Even if you have core samples it would still eventually be pulverized before any analysis can be carried out.Following
- Roger Spurr added an answer:12Can 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!
Hi again look at the minerals you list, these are sublimates from life origins. The silimanite is fascia that has fossilized, see my fossil lung. The DNA tests prove the lung was alive at one time. https://www.youtube.com/watch?v=AROw8rK0WT8
It is a long story but very interesting. Silicon, iron and fascia is the preservative in mud fossils. Here is the wet "mud" fossil process.
1..Wet soils create natural electric currents.
2..Molecular silicates are Tiny, platy and polar, some 2 atoms in size.
3..Creatures buried in mudslides can be sealed anaerobically in cold deep platy polar silicates (mud and clay) influenced by these wet natural electric earth currents.
4...Silicon is 50x higher in skin and connective tissue than other flesh. Si is not found by itself, it is almost always SiO2 and SiO4 which is sand, amourphous quartz and feldspar.
5...Natural electroplating of the creature occurs as Si in the skin bonds and becomes SiO2 and SiO4 (amourphous quartz and feldspars), This occurs on the surface but the insides remain preserved under extreme pressures due to deep mud on top.
6...Leachates from above percolate and interact with the buried creatures exterior surfaces. Chemicals in leachates determine fossil properties. An example is Opal which is a mineralized fossil.
7...Normal oxygenated decomposing bodies literally explode from the gases as they expand. Sometimes skin is "degloved" and Fluids are expelled from weak areas and orifices but very little is expelled in mud fossils due to compaction.
8...As plating continues the surface becomes more and more restricted until OH- becomes the primary invader. OH- is extremely reactive and destroys calcium and phosphorous in bone. This is why bone is hard to recognize in mud fossils.
9...Eventually glacial tilling disassembles the creature along fascial planes and body parts appear.Following
- Pezhman Rasekh added an answer:7Have you visited the portal for dissemination of knowledge in petrography created by Endeeper? PetrographypediA.I would like to receive your comments. http://www.petrographypedia.com/
Thank you all for your attention ... Hope for you the best in your career ...Following
- Maarten A.T.M. Broekmans added an answer:20Is it natural to have Sulphur in Garnet?
I have been observing a metamorphic rock that contain Almandine garnet using SEM-EDS. The presence of garnets is confirmed by the very rock's XRD patterns (both Pyrope and Almandine are present).
Element analysis (SEM-EDS) of various points on Almandine/pyrope shows the following general chemical composition in wt%
Na - 0 - 1% K - 0 - 1 % Al - 17-19%
Mg - 4 -7 % Si - 25 - 30%
Ca - 4 -1 % (Total)Fe - 30 - 35 %
Strangely, Sulphur is there ranging 0 to 2%
Is it natural to have Sulphur in garnet? and are Na, K, Mg and Ca inter exchanging with each other?
Additional Info (XRF analysis (FP method) shows S element about 1.6 wt%. but XRD does not show any peak for possible Sulphur bearing minerals such as pyrite or gypsum. Still the rock samples have strong sulphur smell).
Thank you in advance
Thanks for your reply.
I am not surprised that you don't find any pyrite or gypsum by XRD: the amount of pyrite needed to give off a detectable S-signal in microanalysis is MUCH smaller than your XRD lower limit of detection LLD, which is on the order of 1-5wt%, much depending on sample (notably the type of comminution) and specimen preparation of bulk rock powder, as well as its mineral content. (In fact, modal analysis of bulk powder or powdered rock including trace minerals by XRD can be challenging; eg. check literature on Reynold's Cup!)
Really, by far the most practical method to verify the presence of pyrite inclusions in garnet is optical microscopy, in transmitted light where they will appear opaque, as well as in incident illumination (as suggested by Greg Raab) where they will appear as bright spots if at the surface. Thin- and/or polished-section petrography will also reveal any other S-containing minerals present, which must show up if you report 1.6wt% S by XRF, or alternatively ~4wt% SO3.
To conclude, I confer with Giovanni Ferraris: chemical analysis alone is INsufficient to determine mineralogy. Imagine you are analyzing carbonate by EPMA and find 56wt% CaO (a very good analysis, even when far short of 100wt%), how would you know whether this would be calcite or aragonite (or vaterite)? The simple answer is: by thin-section petrography, which through optical properties provides information on which polymorph you are looking at.
- Gert Nolze added an answer:9What 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?
For accuracy and precision you need to have for all parameters a minimum of error (propagation of uncertainty). If you have band widths of 40 pixels in diameter and your profile is already described by 2 or 3 pixels (the Bragg angles is undetermined and neither a sharp edge, nor there where it is black or where it is still white ) you already have an error in the scale of at least 5 %. This is (from my point of view) also the reason, why this limit is nowadays well accepted. The closer you are going with the detector the worse this ratio becomes. You need to describe band widths in hundrets of a pixel in order to get a valuable accuracy and precision. But how reliable this can be if the band profiles are in the scale of pixels?
The same is valid for patterns center and detector distance. Especially the last one is concerned since at small distances the error becomes dramatically worse because of the low precision of positioning.
If you go to 3-5kV, not only the information depth becomes smaller but also the diffraction conditions become worse (unlimited periodic arrangement of atoms and molecules is less correct), i.e. the bands (if visible) become wider but also more blurred. The determination of the Bragg angle becomes then less accurate, and you also cannot identify that many bands anymore which is the actual reason that you can increase the precision of the technique by using many instead of only a few bands. I only used this example of a few 100V in order to demonstrate into which direction the signal is moving. This blurring is indeed an effect which can be nearly ideally simulated, i.e. an unexpected impact of a bad surface preparation can be excluded. This is also the reason why high resolution images are not much better than 2x2 or 4x4 binned images. The degree in accuracy of band detection is practically not existent because of the pixel width of the profile and uncertainties in band width determination. Unfortunately the profile character is not equal for each band so that one cannot use a simple approximation algorithm for a general Bragg angle positioning. It assumes to be better than a manual, very subjective band edge determination, but it still needs a careful evaluation. The only very accurate information is the a:b:c ratio since zone axes can be really determined in higher accuracy since their distance depends on the screen resolution and can be several hundred or even thousand pixels. Unfortunately they only show you the lattice parameter ration but not the lattice parameters itself. Therfore it is the rule that the ratio is at least 10 times higher accurate than the lattice parameters itself.
The entire procedure is challenging but not hopeless. It perhaps only needs some good ideas :-). Thanks for your comment!Following
- Rinkesh Bhatt added an answer:7How 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?
Dear du Peixin,
I have little bit doubt that the AFM can analyze those surfaces having particle less than 10 nm. If it can than please guide me. I am waiting for the valuable information.
- Valentina Batanova added an answer:5Cr 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? fO2 may be an candidate but I'm not sure ti may be the main reason.
Phenocrysts of Cpx usually have high Cr content. Cr content of CPX depend also from pressure, looks the publications of Paolo Nimis for example.
- Aurelio Sanz Arranz added an answer:12What 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?Following
- Gary Michelfelder added an answer:3Is 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?
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.Following
- Marlina Elburg added an answer:3Where 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.
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!Following
- Thomas Oberthür added an answer:12How 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?
Easiest way - take a magnet.
- Willem Kruger added an answer:5What 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.
Thanks a lot everyone, especially for the article Max! I'll take a look at it.Following
- Sundarrajan Marimuthu added an answer:7Dear 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?
Thanks a lot professor. I will come on further climbs.Following
- Dolores van der Kolk added an answer:7Have 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 IslandFollowing
- V. Divakara Rao added an answer:11What 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
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 .Following
- Mues Huang added an answer:4Why 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.
Thank you all for answering!
- Teresa Diaz Gonçalves added an answer:3Does 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!
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!Following
- Kenneth M Towe added an answer:14What 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!Following
- Tom Jäpel added an answer:23Radiation 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.
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
- Dejan Prelevic added an answer:7Does 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 email@example.com.
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 wellFollowing
- Nirmalya Chatterjee added an answer:16Can 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.
Most probably scapolite!Following
- Govindasamy Usha added an answer:17Is 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.
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.Following
- Sheng-Hong Yang added an answer:12How 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.
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.
For those who interested in rocks, gems, minerals...