- Masoud Ovissi added an answer:26What would be the best approach for finding the Genesis (Origin) of Copper deposit?
I am making proposal on Aynak Copper Deposit, Afghanistan. The genesis for Aynak Copper Deposit is proposed as sediment hosted syngenetic deposit but there are some points (have Intrusion which is felsic to mafic in composition, also the source of magma is unknown whether it was fertile or not) which I think is epigenetic hydrothermal deposit.
I have no idea what would be the possible approach (methodology) to find whether it is Hydrothermal deposit or not. Also mineralogical and geochemical investigation of both mineralized and unmineralized rocks would be helpful for finding the hydrothermal source?
In attachment you can find two other parts of USGS reports entitled:
Analysis of Imaging Spectrometer Data for the Aynak-Logar Valley Area of Interest
Geohydrologic Summary of the Aynak Copper, Cobalt, and Chromium Area of Interest.
- Harry ten Brink added an answer:3Magnetite in fly ash are derived from decomposition+high temp. oxidation of pyrite in combustion boiler. Is decomposition = complete pyrite melting?
In description of fly ash mineralogy it is frequently stated "magnetite crystals in fly ashes are derived from decomposition and high temperature oxidation of pyrite of feed coal in combustion boiler." What does decomposition mean? Is it complete melting of pyrite grains in boiler? Or solid state transformation of pyrite to magnetite without involving melting of pyrite (m.p. of pyrite- about 1180 deg. Celcius)?
Decomposition means that the pyrite FeS2 first becomes FeS, while the "second" sulphur leaves as a gas and is oxidized to SO2
FeS (pyrrhotite) then oxidises
FeS is a liquid and the particles become droplets and therefore the iron-oxide particles are also spherical.Following
- Nibin Tom asked a question:NewCan anyone suggest a reliable chemographic diagram for representing meta-aluminous granite?
The granite is meta-aluminous calc-alkaline with ilmenite, epidote, sphene, biotite, hornblende,plagioclase, microcline (megacrsyts) and quartz (Silica saturated) assemblages. The granite have mingled with basic magma to variable degree. Your suggestions will be valuable and helpful.Following
- Sobhi Nasir 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.
this texture is typical for undersaturated basalt with leucite (poly synthetitc twinning, low burefrengence|) and typical clinpyroxene laths, magnetite and olivineFollowing
- Florentin Paris added an answer:11How to quantify graphite contents in rock powders?
What is a useful method to quantify graphite contents in powdered rock samples? XRD does not work well due to the platy crystals and very strong preferred orientation, so I'm looking for an alternative method. Either by another analytical instrument, or by physical separation, or...
Graphite flakes may be very common in palynological residues after HCl and HF etching of Palaeozoic fine-grained sediments. You can quantify the graphite content by weighting the remaining residue after separation by heavy liquids (remove the pyrite, zircons and other minerals not destroyed during the etching) and separation of the “lighter” organic remains (e.g. acritarchs, spores…)Following
- Jayabalan Manickam added an answer:7Are there any (online or offline) tutorials for GCDkit scripting in 'r' language?
GCDkit is one of the most versatile packages for igneous petrology. Writing scripts in 'r' for GCDkit has a steep learning curve. Tutorials may help to facilitate learning with feedback.
Dear Vojtech Janousek,
Thank you for the information and links.Following
- Vojtech Janousek added an answer:9Does 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.Following
- Zenaide C. G. Silva added an answer:26Does anyone know of a way to estimate mineral proportions based on whole rock analysis?
Is there any software or excel sheet to calculate the mineral proportions (modal % of minerals) based on bulk-rock analysis. Your kind help is highly appreciated.
Have not been using this for a long time, so I can't be helpful. Sorry.Following
- David Cousins added an answer:6Does anyone know about detrital quartz pseudomorphs?
Please see attached file focusing on the detrital quartz grains in a silt laminae of a Paleoproterozoic shale from the Northern Cape, South Africa.
My thoughts are that these are pseudomorphs after something and the 'cracks' are cleavage planes. Other suggestions have been compaction and fracturing, however, I would suspect alignment of the cracks and possibly dismembering of the quartz grains if that were the case.
Any comments or suggestions welcome.
I was unaware of the effects of poor grinding procedures and have learnt a valuable lesson so thank you for your feedback.
Element mapping on these sections confirm that they are in fact quartz grains and not feldspars. I have inspected the thin section thoroughly and the parquet pattern in the quartz occurs closer to the rims of the thin section than in the center. I have also found evidence of quartz from separate provenances but both have the parquet pattern. I conclude that faulty grinding is the best explanation for the patterns.Following
- 2How reliable is a phase differentiation using electron backscatter diffraction (EBSD)?
Typically we distinguish between 6 translation lattices, 7 crystal systems and 14 Bravais lattices. How trustful a phase separation by EBSD can be? Is it possible to say, phases with an F-lattice can be definitely distinguished from an I- or P-lattice, or is this only possible under very special conditions?
I mean some critical problems like shown accidentally a few days ago by Cyril Cayron.Following
- Nibin Tom added an answer:9Sampling strategies for REE and RM exploration?
Can anyone explain the soil/ eluvial and stream sediment sampling procedures for RM and REE exploration. I have not come across a standard operating procedure for REE exploration. Contact between A & B horizon is a thumb rule. But then if no orientation study has been undertaken, How should one proceed. The A & B soil horizons are poorly developed in the area due to sub-tropical climate. Kindly suggest.
Sorry for the delay in response due to field work. Thanks Mr. Om Prakash for your guidance and suggestions. Marlina is right about the xenoxrystic origin of sphene and other REE hosts. The granite ASI index too varies from per-aluminous to meta-aluminous. So two types of sphenes are recorded; other being the altered type. Thank you Francesco and all others for active participation.Following
- Giovanni Ferraris added an answer:11Is a crystallographic translation lattice unique?
Usually a translation lattice is invariant, i.e. one can describe it by different basis vectors, primitive or centered etc., but the arrangement of the lattice points won't change at all, only their indexing. If I have a high-symmetric lattice, and I shift a single atom out of a high symmetric position within the motif describing the lattice point, the symmetry of the point reduces to this low symmetry as well, although the lattice point positions do not change at all. This means, experimentally I have a high-symmetric lattice but a low crystal symmetry. Vice versa it is acceptable as well, that the lattice point has a higher symmetry than the lattice has.
Is it possible to change one or some of several atom positions in a way that the translation lattice changes?
I don't mean joining of lattice points, i.e. reducing the lattice point density by a simple systematic deleting of lattice points.
Dear Gert, cases where the metric symmetry of a lattice (e.g. orthorhombic) is higher than the crystal symmetry (e.g. triclinic, monoclinic) are well known. This is a source of the so called twinnning by metric merohedry. See, e.g., the following page http://www.crystallography.fr/mathcryst/twins.htmFollowing
- H.-J. Förster added an answer:6Why do alkaline melts have high concentrations of incompatible trace elements such as Zr,Nb,Rb,Ti,P?
Why do alkaline melts have high concentrations of incompatible trace elements such as Zr,Nb,Rb,Ti,P?
There ios nothing significant to add to the comments of Martina and Harald. In alkaline melts of whatever type, the major mineral depositories of the elements you mentioned have a much larger solubility with respect to meta- or peralumonous melts. That allows the lement to increase in the course of magma fractionation. The fundamental question is whether the elements typifying those melts are already enriched in their source or gained their larger abundance from specific physico-chemical conditions prevailing in such melts.Following
- Erik B. Melchiorre added an answer:6Alpine Serpentinites: Can You Suggest a good overview article?
Can anyone suggest a good overview article on what makes Alpine Type serpentinites different from others? I know that plots of Cr# vs Mg# have different fields, but what else is different and why? Mineralogy? Any estimates of P-T conditions, or are they variable?
- 11What are the major benefits of TKD (tEBSD) in comparison to TEM investigations, e.g. with ASTAR?
Since for Transmission Kikuchi Diffraction (TKD) in SEM a TEM sample is required, where are the advantages of TKD? If somebody has the opportunity to produce TEM samples he/she should also has a TEM (but maybe no ASTAR).
Does TKD delivers any additional information a TEM cannot supply? What is the typical success rate of a TKD measurement?
Kathrine, in fact you only need a few images and you can calculate the sample surface (e.g. by Alicona or any other software). This is clear, but no standard in EBSD software. It needs some manual operation and a lot of knowledge, how to correct the Euler angles or how samples are tilted. But I appreciate, that you are seriously thinking about it. Many thanks!Following
- Matthew Richard Field added an answer:33Is 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?
Whenever I'm training someone on any microscope, I always tell them that the magnification is only important for taking a bunch of images (on a single instrument) to compare. Otherwise, some post processing scaling is necessary and that can get a bit messy.
Also, like Vladamir mentioned earlier, sometimes scale bars get messy when using SEMs. In my experience, for a single mag, sometimes the software likes to jump between (for example) 10um or a bar that is twice as long but is 20um. The key thing to remember is that by changing the screen size, printing onto paper, etc etc, you are changing the magnification of the image! (Also watch out for quad screen mode in the SEM software...)
It is always the scale bar which is the most important . I would never include the magnification in my work.Following
- Reyhaneh Ahmadirouhani added an answer:3Spot data are needed to compile with ASTER for better identification of pegmatites in hardly accessible terrains. Are there interested collaborators?
Spot data are needed to compile with ASTER for better identification of pegmatites in hardly accessible terrains. Are there interested collaborators?
Dear Dr. Zoheir,
The scale of the map you want prepare is important, for 1:100.000 or near this scale you can use only ASTER but for 1:25000 and 10.000 you need merge SPOT- pan or IRS-pan with ASTER or landsat.
SPOT is also good for extract leanation and structural features.because it has stereo viewFollowing
- 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
- 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.
- 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
For those who interested in rocks, gems, minerals...