Learning Center What is a mineral?The most common minerals on earth Information for Educators Mindat Articles The Elements The Rock H. Currier Digital Library Geologic Time

Minerals by Properties Minerals by Chemistry Advanced Locality Search Random Mineral Random Locality Search by minID Localities Near Me Search Articles Search Glossary More Search Options

The Mindat Manual Add a New Photo Rate Photos Locality Edit Report Coordinate Completion Report Add Glossary Item

Mining Companies Statistics Users Mineral Museums Clubs & Organizations Mineral Shows & Events The Mindat Directory Device Settings The Mineral Quiz

Photo Search Photo Galleries Search by Color New Photos Today New Photos Yesterday Members' Photo Galleries Past Photo of the Day Gallery Photography

Discussions

💬 Home 🔎 Search 📅 Latest

╳Discussions

💬 Home 🔎 Search 📅 Latest

Groups

Recent Images in Discussions

Identity HelpUnknown EDS help

7th Jan 2017 12:09 UTCJoshua Chambers

Hi all

This specimen is from Folgosinho, Portugal ( http://www.mindat.org/loc-132561.html ). The mineral in question is the pale blue botryoidal mineral to the left of the picture.

I'm thinking that it might be some kind of Fe-sulphate and the O not detected?

Thanks

Josh

7th Jan 2017 12:16 UTCReiner Mielke Expert

It is a very compressed spectrum, difficult to say what you are seeing at the low end. For sure it is not a sulphide but is it possible you got some contamination from the black stuff? Either way it is obviously very distorted, way too much Fe. I would suggest getting it reanalyzed.

7th Jan 2017 12:28 UTCJoshua Chambers

Hi Reiner, thanks for the reply.

Ok, that makes sense. I thought the spectrum looked strange. I may get it reanalysed in the future.

In fact, I did also get the black/brown aggregate analysed as well, it also has a high Fe peak; as its in the same picture any ideas for the brown mineral? Perhaps a Mn-bearing phosphosiderite?

Thanks

Josh

7th Jan 2017 12:40 UTCReiner Mielke Expert

That's a tough one since there are so many iron phosphates and the color may be due to Mn oxide inclusions. Can't see anyway of resolving that without XRD. I wish I could be more helpful.

7th Jan 2017 13:03 UTCJoshua Chambers

Ok, so there's another sample for future XRD analysis (I have way too many) :-D. Thank you for the help anyway.

Interestingly, there was another aggregate on the specimen which looked very similar to the brown aggregate I just showed. The spectrum came back with similar results (ignoring contaminants), but with a huge C peak; what do you think of this one?

Thanks for the help

Josh

7th Jan 2017 13:10 UTCReiner Mielke Expert

Could the carbon be from the mount? Some people use carbon tape to mount the samples. Either that or you have some graphite mixed in with an iron phosphate.

7th Jan 2017 13:36 UTCJoshua Chambers

Ahh yes, you might be right. I couldn't remember if it was the mount that was carbon, or something else.

I might as well post the last unknown from the same specimen. Here is a black botryoidal mineral on purple (i think) strengite

Any ideas? Looking at it now, I'll probably have to get this one XRD anlaysed as well

Thanks

Josh

(EDIT: After looking at pictures from the locality, the bl;ue mineral with distorted spectrum looks very much like this phosphosiderite: http://www.mindat.org/photo-54126.html .)

7th Jan 2017 14:16 UTCReiner Mielke Expert

Hello Josh,

Could well be phosposiderite with MnO inclusions but there is no way of proving it with the data you have. As for the latest picture and EDS, same problems as before except this time it looks like more MnO. The photo of the material in question does not look like a single phase to me rather a mixture. XRD should help with this. I run into this sort of thing all the time, wish it were easier.

I commend you are making a serious effort, most collectors can't be bothered. Just a friendly warning though, you better have a thick skin. I am constantly annoyed by the fact that if you do not provide any supporting evidence for your conclusions no one questions your ID ( unless it is very obviously wrong) . For example just going with a dealer's label no questions asked is OK. But once you present any supporting data like EDS all of a sudden people jump all over you questioning your ID. Sure EDS may not be conclusive but then it is a lot closer to the truth than no EDS and just a dealers label. I find these "attacks" very discouraging and counter productive if you ask me. Best of luck.

7th Jan 2017 14:49 UTCJoshua Chambers

Thanks for the reply Reiner.

What makes it look like a mixture to you? How do you tell the difference? Just experience?

Something I enjoy about collecting minerals is buying something and then finding a load more 'bonus' minerals around the specimen; this is half the fun for me. The crystals don't have to be perfectly crystallised and shaped, just the fact that they are there in association with other minerals interests me. This teaches me what kind of minerals can be found with one another.

I do understand what you are saying and will be prepared for the future. In the past I've bought stuff from shops and found them to be incorrect ID's (to much dissapointment), so I would much rather get it analysed to get closer to the true ID than leave it as unknown; I'd much rather an unknown FeMnPO4 than an unknown brown mineral. I don't get this much anymore because my knowledge has grown so much and I'm not as gullible :-D

Thanks for all of your help

Josh

7th Jan 2017 14:58 UTCReiner Mielke Expert

Hello Joshua,

When I look at the photo I do not see a uniform color and it looks granular to me, which suggests there might be more than one phase. I agree with you on finding surprises. The use of EDS makes the hobby so much more interesting at a reasonable cost. I have found lots of bonuses as a result of probing more deeply into what I buy and collect. As you have found, looking at things on a microscopic level opens up a whole new world. You can go on a collecting trip to an exotic locality just with a hand specimen and a microscope. Lots of fun.

7th Jan 2017 17:12 UTCJoshua Chambers

I understand now, didn't know about that, thanks.

I agree, about EDS making it a bit more fun. Seeing what your own minerals are made from specifically is really interesting to me. For example, I have some zircon from Mt Malosa which has lots of Y in it, Y-bearing zircon. I would never have found this out without EDS. Viewing most specimens under magnification can be really quite amazing and it's so easy to do. Then again, you only have to look at the majority of 'photo of the day's to realise that under magnification, the real beauties lie (that's ignoring the large amounts of money put into taking the amazing pictures).

Thanks

Josh

7th Jan 2017 17:43 UTCD. Peck

Hi Josh, I am almost completely ignorant of how to interpret EDS. But I looked at your first photo (the light blue, botryoidal) and ran "blue", "botroiydal", "Fe" through my database (4000+ minerals). It came up with only three minerals: Aheyite, chalcophanite, and vivianite. The first two both contain zinc and I can't imagine the EDS missing that. The vivianite , of course, is a phosphate and that might be a possibility. I am enjoying the discussion between you and Reiner. If I keep reading, I may learn something and give EDS a try.

7th Jan 2017 18:23 UTCJoshua Chambers

Hi Don

Yes, vivianite is very much a possibility, along with strengite as well. I don't know if you saw an earlier message, but I found this photo of phosphosiderite from the same locality looking very similar to my unknown ( http://www.mindat.org/photo-54126.html ). I may PM the owner of the photo and asked if he analysed it.

I've only very recently used EDS. This was analysed with another 13 or so samples in November by a kind individual who did it for nothing. This is my first time experiencing EDS and probably the last time for a while. Although EDS sometimes can't ID a mineral on its own (like in this situation) it will most of the time narrow down your answers and give you the primary elemental constituents of the material. It's also very interesting trying to look for minerals that contain the elements shown in the spectrum, but also time consuming and sometimes disappointing if you need more analyses done.

The best way to learn is by experience, so why not try it. There's plenty of places which do it, the downside is that it sometimes costs money, although not a lot, it's still money.

Thanks

Josh

7th Jan 2017 19:30 UTCTorfinn Kjaernet

Hi Josh. I have recently been running PXRD on a lot of the phosphates in my collection and bluish to pinkish blue botryoidal aggregates from different localities looking visually very similar to your Folgosinho sample above all turned out to be phosphosiderite. However I did not run PXRD on the Folgosinho samples I have as they visually looked so similar to the analyzed phosphosiderites so I assumed that it too was phosphosiderite. I am sure there are several alternatives but I think a good guess ( without a PXRD of your sample) would be that it is phosphosiderite. Phosphosiderite is also a common mineral in Folgosinho. Torfinn

7th Jan 2017 19:49 UTCJoshua Chambers

Hi Torfinn

Thank you for the information. That's really helpful. I will note it down as phosphosiderite until I can confirm.

Thanks

Josh

7th Jan 2017 21:25 UTCPedro Alves Expert

Hello Joshua,

pale blue botryoidal mineral is phosphosiderite. I think that the Mn peak is due to a thin coating of a Mn hydroxide (you can see that in the right side of the first picture). The C peak is, generally, due to the coating as well to the hand manipulation.

In the second picture the 'black' material looks like rockbridgeite (rockbridgeite-frondelite), instead of a Mn hydroxide.

Cheers,

Pedro

7th Jan 2017 21:52 UTCJoshua Chambers

Hello Pedro

Thanks for the reply. The right side of the first picture (brown mineral) you say is the phosphosiderite coated with Mn hydroxide, right? However, that was also analysed and came back as a FePO4 ( link to spectrum of brown mineral in 1st picture: http://www.mindat.org/forum.php?file,11,file=68549 ). Or is it likely the brown mineral sample was contaminated with the phosphosiderite, so shows spectrum of phosphosiderite and Mn hydroxide. That would explain the relatively high Mn peak and other contaminants of Ba, Si & Al?

Thanks

Josh

7th Jan 2017 21:56 UTCPedro Alves Expert

hello Joshua,

Ba , as well as K and Na are expectable for Mn hydroxides of the coronadite group. For Si and Al, i think it's a contamination from the matrix.

Cheers,

P.

7th Jan 2017 22:17 UTCJoshua Chambers

Hi Pedro

OK, that would make sense.

Thank you very much

Josh

7th Jan 2017 23:13 UTCAlfredo Petrov Manager

Don't forget that Mn and Fe can replace each other in many mineral structures, so the presence of some Mn in an Fe-phosphate is not surprising at all, and not necessarily due to contamination of the sample.

7th Jan 2017 23:26 UTCPedro Alves Expert

Hi Alfredo,

you are absolutely right, however Mn substitution is minerals like strengite or phosphosiderite is not that common. By contamination i men a thin coating (something we can actually see in the first picture).

Cheers,

P.

7th Jan 2017 23:31 UTCPedro Alves Expert

By other side, Fe-Al substitution is more than expectable for strengite (Strengite-variscite series).

7th Jan 2017 23:34 UTCAlfredo Petrov Manager

You could remove the Mn oxide coating with slightly acidified hydrogen peroxide, and then shoot the clean phosphate again.

7th Jan 2017 23:38 UTCPedro Alves Expert

Yes, or you can try an EDS on the inner part. Maybe you'll find out that the spheroid is zoned (Fe/Al decreasing from the core to the border).

Mindat.org is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization.
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2024, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters. Founded in 2000 by Jolyon Ralph.
Privacy Policy - Terms & Conditions - Contact Us / DMCA issues - Report a bug/vulnerability Current server date and time: May 4, 2024 22:36:09

Go to top of page