How to ID minerals http://www.mindat.org/msgboard-100.html Thu, 26 Nov 2009 01:17:00 +0000 Phorum 5.2.8-RC1 http://www.mindat.org/forum.php?read,100,160423,160423#msg-160423 http://www.mindat.org/forum.php?read,100,160423,160423#msg-160423
I have done a Rietveld refinement with the help of a PANalytical X'pert Pro but the standard configuration is giving me a lot of troubles.
I am no engineer, so the inner workings of that machine are somewhat a mystery to me. I am asking if someone else has used a PANalytical for Rietveld and if you can give me a better configuration of slots, masks etc.

Please take into consideration while writing your reply that I'm still a student and I have yet a lot to learn.

Thank you!]]> Alexandra Catalina Seclaman Analytical Techniques Wed, 25 Nov 2009 18:53:59 +0000 http://www.mindat.org/forum.php?read,100,159207,159207#msg-159207 http://www.mindat.org/forum.php?read,100,159207,159207#msg-159207
I m looking for some lab performing lead isotope studies (ICP-MS with magnetic sectors?). We would like to date source of hydrothermal mineralization where only mineral suitable for dating is galena. I know this technique is a little bit out-of-date, but we have no uraninite, zircones, monazites, feldspars etc. I will be grateful for any advice.

Thanks.]]> Jakub Jirásek Analytical Techniques Mon, 16 Nov 2009 09:48:38 +0000 http://www.mindat.org/forum.php?read,100,158740,158740#msg-158740 http://www.mindat.org/forum.php?read,100,158740,158740#msg-158740 I have access to an X-ray spectrometer which is generally used to test metal fineness and rhodium thickness etc. My question is whether this machine has any application in testing gemstones, for instance if I put a sapphire down on the eye and the machine showed Be is present would this be a reliable way to asess treatment with beryllium? Is there any software that is compatible with this machine that focuses more on gems than metal?? Any assistance would be greatly appreciated, thanks!!]]> Nate Alger Analytical Techniques Thu, 19 Nov 2009 20:46:39 +0000 http://www.mindat.org/forum.php?read,100,157610,157610#msg-157610 http://www.mindat.org/forum.php?read,100,157610,157610#msg-157610
I have microprobe data on several monazite grains that I would like to plot up as a monazite-huttonite-cheralite ternary diagram. Unfortunately, I can't find many resources on how one divides up the elements between the end members. I have the recent paper by Linthout, which offers a few clues, but I suspect it isn't the whole story, with much of the process being assumed information for people reading the paper. It seems much more complex than the standard amphibole calculations, etc.

I have tried to work it out the following way. It's certainly not very good, but it seems to give answers that plot with monazites from similar settings:

Divided Wt% elements by atomic number, giving relative mol amounts (I doubt this is quite right, can't be this easy)

REE, Al, Y into Monazite
Ca, Pb, Sr, Fe, U into Cheralite (don't know the valence of Fe, but amount is quite small)

All Si into Huttonite, use this value to figure out the required amount of O and Th
Use (Ca, Pb, Sr, Fe, U, remaining Th) to figure out P and O needed for Cheralite component

The left over P and O needed to balance out the Monazite components is pretty close, though there is a small amount left over. What is the right way to do this? I imagine this method might make a few people laugh, but it's the best I could think of :(

Here's an analysis of one of the monazites in weight percent:

Si 0.04
Al 0.01
K 0.03
Fe 0.01
Ca 2.93
Sr -0.06
Pb 0.64
Y 1.39
Th 8.15
U 7.97
La 6.48
Ce 14.40
Pr 1.77
Nd 6.18
Sm 4.49
Eu -0.17
Gd 3.48
Dy 0.95
Yb 0.05
Er -0.01
P 12.80
S 0.00
As -0.02
O 26.65
Total 98.41

I get a composition of 38.3% Monazite, 61.3% Cheralite, .3% Huttonite from this one. Someone come and tell me how wrong I am please :)]]> Ryan Eagle Analytical Techniques Fri, 20 Nov 2009 00:14:11 +0000 http://www.mindat.org/forum.php?read,100,156491,156491#msg-156491 http://www.mindat.org/forum.php?read,100,156491,156491#msg-156491
The pyrometamorphic hematite is known to contain Al (corundum part) as well as Mg and Ti (and Si), thus we have here the Fe₂O₃-Al₂O₃-MgO-TiO₂ system. Hematite-ilmenite would probably (?) fit into this system. However, the recent find of tistarite (Ti₂O₃) made me think.... is the hematite-tistarite miscibility possible in such a system? These two minerals possess the same space group. Ilmenite "slightly" differs, but, from the other side, miscibility in the hematite-ilmenite system is known in the literature.

What do You think?

Thanks a lot,

L. K.]]> Łukasz Kruszewski Analytical Techniques Mon, 19 Oct 2009 12:52:40 +0000 http://www.mindat.org/forum.php?read,100,156303,156303#msg-156303 http://www.mindat.org/forum.php?read,100,156303,156303#msg-156303 Nate Alger Analytical Techniques Mon, 19 Oct 2009 18:52:31 +0000 http://www.mindat.org/forum.php?read,100,155087,155087#msg-155087 http://www.mindat.org/forum.php?read,100,155087,155087#msg-155087 Henry Barwood Analytical Techniques Tue, 10 Nov 2009 15:55:20 +0000 http://www.mindat.org/forum.php?read,100,154378,154378#msg-154378 http://www.mindat.org/forum.php?read,100,154378,154378#msg-154378 Joseph Taggart, Jr. Analytical Techniques Fri, 09 Oct 2009 17:16:37 +0000 http://www.mindat.org/forum.php?read,100,152631,152631#msg-152631 http://www.mindat.org/forum.php?read,100,152631,152631#msg-152631
Thanks Andrew J.]]> Andrew Johns Analytical Techniques Sun, 11 Oct 2009 04:48:58 +0000 http://www.mindat.org/forum.php?read,100,151910,151910#msg-151910 http://www.mindat.org/forum.php?read,100,151910,151910#msg-151910
I wasn't aware of the identities when they were first given to me. They look pretty much the same. They seemed to have the same shade, they both had sharp facets and sparkled quite nicely. The only differences I could see under close examination was one had visible flaws which gave it the effect of seeming more faceted, while the other did not. I assumed the one with the flaws was an actual diamond, and this was confirmed when I later found the tag that came with it.

I was skeptical of the flawless stone based only on the fact that such a flawless diamond of that size seemed too unusual. Out of sheer curiosity I took it to a jewelry who's family had been in the business for generations, and he was able to tell me in about five seconds looking through an eye loop in the dim light that it was cubic zirconia.

My question is, how did he do that? What is it that tipped him off?]]> Jenna Mast Analytical Techniques Fri, 13 Nov 2009 04:34:06 +0000 http://www.mindat.org/forum.php?read,100,146508,146508#msg-146508 http://www.mindat.org/forum.php?read,100,146508,146508#msg-146508
Would any of you instrumentalists out there care to take it on....and for what fee?

Don S.]]> Don Saathoff Analytical Techniques Mon, 28 Sep 2009 22:40:46 +0000 http://www.mindat.org/forum.php?read,100,142989,142989#msg-142989 http://www.mindat.org/forum.php?read,100,142989,142989#msg-142989
Now consider an EDS analysis that returned the following Wt % oxides:
Y2O3 9.51%, Nb2O5 16.47%, ThO2 2.38%, UO2 3.91%, CaO 5.21%, TiO2 18.02%, Nd2O3 3.66%, Ce2O3 1.79%, La2O3 1.20%, Fe2O3 2.59%, Ta2O5 35.25%.

From this, I derived structural formulas, with the best fit based on six oxygen atoms:
(Y+REE0.447 Ca0.366 Fe0.142 U0.057 Ce0.043 Th0.036){1.091} (Ti0.889 Ta0.629 Nb0.488){2.007} O6

I will become rapidly clear that if it's betafite, there is a problem. For one, betafite has two atoms at the A site, while my best fit provides only one. The next problem is that my specimen is Ti>Ta>Nb, compared to Ti>Nb>Ta for betafite. In fact, I could find only one Ti>Ta>Nb mineral poking around Strunz & Dana (it's not even close *and* it was discredited in 1977).

The A site is dominated by Y, so let's consider for a moment betafite-(Y). Just in terms of elemental composition, my sample is fairly close to yttrobetafite-(Y) *except* for Ta>Nb, two A site atoms vs. one, and the XRD pattern for yttrobetafite-(Y) is a very poor fit.

Suggestions? Ideas?]]> Fred E. Davis Analytical Techniques Sun, 02 Aug 2009 16:02:58 +0000 http://www.mindat.org/forum.php?read,100,142686,142686#msg-142686 http://www.mindat.org/forum.php?read,100,142686,142686#msg-142686
How can I determine the location of cations such as Ca Mg (a carbonate mineral) ? Are there any techniques to define their location (even their surface abundance on crystal structure is sufficient for me ) ?

Pls note that I have this sample in clay material, meanly it is not "pure". And it seems impossible to clean other impurities ...

Any suggestion ?

Thanks,
Mustafa
Student]]> Mustafa Analytical Techniques Tue, 23 Jun 2009 19:47:29 +0000 http://www.mindat.org/forum.php?read,100,140938,140938#msg-140938 http://www.mindat.org/forum.php?read,100,140938,140938#msg-140938 Thanks]]> Bryan Manke Analytical Techniques Sat, 27 Jun 2009 13:38:56 +0000 http://www.mindat.org/forum.php?read,100,137236,137236#msg-137236 http://www.mindat.org/forum.php?read,100,137236,137236#msg-137236
Does anyone have tips for consistently seating the top and removing the excess water to get good precision?]]> Donald Peck Analytical Techniques Tue, 07 Jul 2009 15:23:13 +0000 http://www.mindat.org/forum.php?read,100,136538,136538#msg-136538 http://www.mindat.org/forum.php?read,100,136538,136538#msg-136538
thank you]]> Charlie Mc Analytical Techniques Wed, 06 May 2009 11:09:58 +0000 http://www.mindat.org/forum.php?read,100,136445,136445#msg-136445 http://www.mindat.org/forum.php?read,100,136445,136445#msg-136445
The test as described in “Handbook of Chemical Microscopy” by Chamot and Mason, begins with evaporating a drop of the unknown solution to dryness, and covering it with acetic acid. Then a crystal of copper acetate is added and allowed to dissolve. Then a small amount of sodium acetate is added. After this has dissolved, a crystal of potassium nitrite is placed into the center of the drop, and the slide is watched for the appearance of black cubes or square flattened tablets indicating the presence of lead in the unknown sample. The test can be modified to test for copper by leaving out the copper acetate and using lead acetate instead. It can be used to test for potassium by including both lead acetate and copper acetate and substituting sodium nitrite instead of potassium nitrite. The test works very well in any of these three variations, but it’s versatility only begins there. The crystalline precipitate contains lead, copper and potassium, but there are a number of other cations that can substitute, each producing crystals with characteristic color.

This is obviously a valuable test to have at one’s disposal, the problem, as previously mentioned, is that unless you have access to a chemistry laboratory, it’s unlikely that you have all the chemicals needed. The good news is that there are substitutes that work quite well that almost everyone can get easily. The first substitution is to use distilled white vinegar in place of the acetic acid, and baking soda in place of the sodium acetate. In addition, the lead and copper ions need not be supplied in the form of acetates. Chlorides or nitrates work quite well. The important thing is that the reaction needs to be carried out at a fairly neutral pH. That’s the reason for using the acetic acid-sodium acetate buffer system for dissolving the ions. Potassium nitrite is the essential ingredient for the test, but if all you have is sodium nitrite, using a mixture of equal amounts of potassium chloride and sodium nitrite works just as well. In this case, the potassium and the nitrite come from different salts, but the crystals produced don’t seem to care. Substituting cesium chloride for potassium chloride makes the test much more sensitive, though the crystals produced are smaller.

The excellent description of this test in Chamot and Mason, indicates that this test can be used to detect the presence of potassium, rubidium, cesium, thallium, lead, calcium, strontium, barium, copper, cobalt, nickel, and ammonium. All except cobalt produce crystals that include three ions. Cobalt forms a yellowish or reddish fine crystalline precipitate of a double nitrite salt with just one of the ions from the potassium group (potassium, ammonium, rubidium, cesium, or thallium). Otherwise, the crystalline precipitate includes three ions, one from the potassium group, one from the lead group (lead, calcium, strontium, or barium) and one from the copper group (copper, cobalt, or nickel). Not all of these combinations form crystals with equal ease. For some combinations, the concentrations need to be just right for the crystals to form, and some do not make themselves visible until the test drop has evaporated almost to dryness, if at all.

As a test for lead, cesium, potassium, rubidium, strontium, ammonium, nickel, cobalt or copper the triple nitrite test is excellent. I found the results for calcium, and barium to be less predictable. Thallium was not tested in this series of experiments, but based on the description in Chamot and Mason, the triple nitrite test probably responds to the presence of thallium with high sensitivity. Since using cesium chloride instead of potassium chloride makes the triple nitrite test more sensitive, often adding a crystal of cesium chloride to the drop will induce a marginal mixture to produce crystals.

Interpreting the results of this test can be a little confusing. With so many possibilities, some creativity can be exercised in devising a system. The following outline is adapted from the procedure described in Chamot and Mason.

1. Prepare the sample by placing a drop of the unknown solution on a slide and evaporate it to dryness. Add a drop of acetic acid (vinegar), and a bit of sodium acetate (or baking soda). Stir it so that everything dissolves. If you use vinegar and soda, don’t add too much soda. The solution should still have some fizz when you add the last bit of soda.
2. Add a crystal of sodium nitrite.
a. A fine reddish or yellow precipitate means cobalt and one of the potassium group ions is present.
b. Black or green plates and cubes means at least one member of each of the three groups is present. Lead makes intense black crystals.
c. White granular precipitate can mean lead with mercury plus one of the potassium group ions.
3. If no precipitate so far, add potassium nitrite (potassium chloride plus sodium nitrite)
a. Reddish or yellowish fine precipitate means cobalt (or rhodium)
b Yellow (green) plates and cubes means Sr or Ba and Ni or Cu.
c. Black plates and cubes means lead and one of the copper group.
d. White granular precipitate means mercury and one of the lead group.
4. If still no precipitate, add copper acetate (chloride)
a. Black plates and cubes means lead is present.
b. Green plates and cubes means strontium or barium.
5. If still no precipitate, add a crystal of cesium chloride.
a. Green plates and cubes means calcium, or one of the lead group in low concentration.
b. Black plates and cubes, means lead in low concentration.
5. If there is still no precipitate, prepare a new slide with the unknown, and add lead acetate (nitrate) and potassium nitrite (sodium nitrite and either potassium or cesium chloride)
a. Black plates and cubes means copper or nickel is present.

If silver is present in the unknown, it may cause the separation of long slender needles of silver nitrite when the potassium or sodium nitrite is added, or if there’s very much silver, insoluble silver acetate may cause the sample to refuse to dissolve.

Too much antimony, bismuth, cadmium, or mercury can cause problems.

Aloha,
Jesse]]> Jesse Crawford Analytical Techniques Thu, 16 Jul 2009 15:17:38 +0000 http://www.mindat.org/forum.php?read,100,135906,135906#msg-135906 http://www.mindat.org/forum.php?read,100,135906,135906#msg-135906 I don't need quantitative tests just qualitative. though I suppose a test like that won't be simple]]> Donald Vaughn Analytical Techniques Mon, 04 May 2009 11:07:00 +0000 http://www.mindat.org/forum.php?read,100,132677,132677#msg-132677 http://www.mindat.org/forum.php?read,100,132677,132677#msg-132677
I was reccomended to send it to Virginia Polytech. But I dont know a contact there. I would also like to send it to Caltech to George Rossman of Tourmaline fame, but he does not know me. So in the interim I am looking for an in exspensive way to do:
1) Age testing
2) Thin Section Microscopy (cross polar)
3) Mineral and element identification.

I would know more about these rocks but for the last 14 years noone has ever seen it and I cant find any pictures (other than mine) on the internet of similar materials that werent created in a test tube or generated digitally with a computer algorythm. The material is washing up on a beach so I can't find the collection site. When I posted it to the Mineral ID I got almost no information on it. (I thought someone should know something...) as for now I am the world leading authority on this un-named/ un-known enigma rock group and I have over 500 specimens. If new I would very much like to name the material "quasarite" if known I would be just as happy to know (finially) what it is.
Any help would be greatly appreciated. Gentlemen, I realize I am in way over my head here and this is very potentially the wrong forum to ask these beginner questions. I had posted to the other forums and could not get an informed oppinion.
-Matthew Boeck
San Diego]]> Matthew Boeck Analytical Techniques Tue, 21 Jul 2009 16:00:17 +0000 http://www.mindat.org/forum.php?read,100,131836,131836#msg-131836 http://www.mindat.org/forum.php?read,100,131836,131836#msg-131836
Of course, if you are lucky enough to have a TGA apparatus that normally uses a flow of nitrogen, then this is a moot point!

Henry]]> Henry Barwood Analytical Techniques Thu, 26 Mar 2009 15:43:26 +0000 http://www.mindat.org/forum.php?read,100,130789,130789#msg-130789 http://www.mindat.org/forum.php?read,100,130789,130789#msg-130789 Donald Peck Analytical Techniques Wed, 25 Mar 2009 14:53:56 +0000 http://www.mindat.org/forum.php?read,100,130117,130117#msg-130117 http://www.mindat.org/forum.php?read,100,130117,130117#msg-130117 Steve Rudloff Analytical Techniques Thu, 12 Mar 2009 17:52:56 +0000 http://www.mindat.org/forum.php?read,100,129977,129977#msg-129977 http://www.mindat.org/forum.php?read,100,129977,129977#msg-129977 have you ever Tryed to hold a blue 405 nm Laserpointer (1 mW or max. 5 mW!) on a Specimen?

You should try it.

Calcite has a red Fluorescence under LW UV, but you cant see any Phosphorecence due Delay of Eye Adapting if you shut of the Source. If a Laserdot moves around the specimen you see its a Phosphorescence of several Milliseconds. The laser draws a red Tail on the calcite.

Painite dont show a Fluorescence under common Sources. But unter a Laser you can see on some Painites a light red Fluorescence.

Alexandrites dont show much fluorecence. Mostly you cant see anything. But the laser shows even on brazilian specimens a light red fluorescence.

Scheelithe dont gives any UV efect on LW? The laser shows on chinese brown specimens a light orange lighting.

It has the potential to be a revolutionary new Tool for Testing Specimens.
Greets
Alexander Ringel]]> Alexander Ringel Analytical Techniques Wed, 11 Mar 2009 17:16:17 +0000 http://www.mindat.org/forum.php?read,100,129943,129943#msg-129943 http://www.mindat.org/forum.php?read,100,129943,129943#msg-129943
Disclaimer: Mercury, mercuric oxide, mercury thiocyanate, and nitric acid are dangerous materials. Be careful.

If you have mercuric thiocyanate and potassium thiocyanate, then making potassium mercuric thiocyanate is quite simple. Combine them in the ratio calculated by comparing their formula weights. Mercuic thiocyanate (317), and potassium thiocyanate ( 97) or 3.27 to 1 by weight. Mercuric thiocyanate is not very soluble in water, but dissolves in dilute hydrochloric acid. Simply dissolve them, combine the two solutions, and harvest the crystals.

A slightly more involved procedure begins with mercury (or mercuric oxide), nitric acid, and potassium thiocyanate (or ammonium thiocyanate and potassium hydroxide).

Overview: Dissolve the mercury (or mercuric oxide) in a slight excess of nitric acid. Then dissolve the potassium thiocyanate in water and combine it with the mercuric nitrate solution. Harvest the crystals of potassium mercuric thiocyanate.

Here's a recipe that yields about 20 grams:
Dissolve 12 grams of mercury (or 13 grams mercuric oxide) in not less than 8 ml concentrated nitric acid. More is ok, say 15 or 20 ml or so. Add a little water to the solution and filter any insoluble residue that remains after the mercury is dissolved. Dissolve 10 grams of potassium thiocyanate in 25 ml of water, and combine with the mercuric nitrate solution. Harvest the crude crystals of potassium mercuric thiocyanate, and recrystallize them from water.

If what you have is ammonium thiocyanate instead of potassium thiocyanate, then combine 13.7 grams of ammonium thiocyanate with 10 grams of potassium hydroxide in 25 ml of water. Warm the solution and let it sit long enough for the ammonia to finish evolving, and use this solution in place of the potassium thiocyanate solution in the above recipe.

The water amounts aren't critical. It's important to remember that mercuric nitrate will precipitate as an insoluble basic salt from solution if the pH goes too high, so be sure that it's always kept in acid solution until it's combined with the thiocyanate . It's possible that the yield could be higher if you neutralize the excess acid after combining the mercuric nitrate and the thiocyanate solution, however I have not found that to be necessary.

Thiourea, another handy reagent, is easily prepared by heating ammonium thiocyanate to 150 degrees centigrade, for an hour or so. Then recrystallize the thiourea from water.

Be careful. Poisonous oxides of nitrogen are evolved when mercury reacts with nitric acid. All mercury compounds are poisonous. The danger with mercury is not so much that it will kill you. It can, of course, but it's more likely to just shave a few points off your IQ. Don't take chances.

Aloha,
Jesse

If you're not having fun, you're not doing it right.]]> Jesse Crawford Analytical Techniques Mon, 16 Mar 2009 10:42:55 +0000 http://www.mindat.org/forum.php?read,100,126915,126915#msg-126915 http://www.mindat.org/forum.php?read,100,126915,126915#msg-126915
Analytical Techniques

be added to the list of subject areas.

Topics for discussion might include:

Microchemical tests (and Ring Oven tests)
Physical property tests (hardness, specific gravity, etc)
Spectroscopy
Polarized Light Microscopy
Optical Microscopy
XRD
XRF (and EPMA)

Admittedly, the readership might be a bit limited, but would be worth a look to at least a few readers.

Henry]]> Henry Barwood Analytical Techniques Tue, 03 Mar 2009 15:29:30 +0000