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Improving Mindat.orgWrong identity and wrong location

5th Aug 2013 19:26 UTCJohn Sobolewski Expert

Pictures http://www.mindat.org/photo-236981.html, http://www.mindat.org/photo-236987.html, and http://www.mindat.org/photo-236992.html show typical specimens of Hematite from the Irhoud Mine, Morocco and not Goethite from the Mibladen Mining District. John S.

6th Aug 2013 10:13 UTCKnut Edvard Larsen 🌟 Manager

A question about these has been raised before see http://www.mindat.org/mesg-7-282395.html. And messages been sent earlier

These are definitively not from Mibladen, but I am not sure if they are from Irhoud. It may be, but i saw that similar specimens was offered for sale at the Vein 12, Taouz locality during the 2. Mindat. org conference and goethite (not polished as these) were seen abundantly at the dumps there.

However, since Mibladen is not correct, I changed all from Midbladen to Irhoud with a note in the caption.

6th Aug 2013 20:32 UTCJohn Sobolewski Expert

Knut,

What you say is interesting. You are correct that at Taouz there are a lot of dull black (and not the naturally lustrous) botryoidal oxides on the dumps but all the ones I have purchased in Tucson from Taouz proved to be manganese oxides with a black streak and not a yellowish or rust red streak indicative of Goethite.or Hematite. This implies that some of the photos of dull black oxides from that locality identified as Goethite or Hematite may be misidentified and be really manganese oxides. A simple streak test can tell the difference.

As for the naturally lustrous Hematites, well known Tucson dealers specializing in Moroccan minerals tell me they are from the Irhoud Mine and not from Taouz. But they may also exist at Taouz, although the fact that they were on sale at the Taouz vein 12 locality does not mean they were necessarily from there. The availability of specimens at a given location does not imply they are all local. John S.

7th Aug 2013 00:00 UTCMark Heintzelman 🌟 Expert

John,

I do have to wonder though if perhaps the third one, http://www.mindat.org/photo-236992.html isn't actually goethite after all. It's subtle, but that one looks to have a more typical black glassy appearance rather than the sub-metallic, greyish reflectance as Hematite often does. (could just be my mistake and is just the particular lighting on that one).

I've seen this jet black glassy surface exhibited by goethite at many other localities, one of my favorites being the material from the Oregan Iron Mine, NW of Cockeysville in Maryland, USA.

As mentioned, a streak test is all that is really required to make these necessary corrections (unless it streaks black and is more likely a high manganese mix, cryptomelene or the like (?). All three of these are from one contributer, so it shouldn't be problematic to take care of this. :D

MRH

7th Aug 2013 19:35 UTCJohn Sobolewski Expert

Mark,

The main issue was that these were not from Mibladen. As you say, sometimes the difference between Hematite and Goethite can be subtle but a streak test should help in determining which species it is.

In looking at the photos of Goethite from Taouz, it looks like some of them should be checked because they are more likely to be manganese oxides which are plentiful at this locality. Photos 59686 (although this one says it may be cryptomelane which to me says that it most probably is), 88343, 88345, and 388038 are examples. Many Moroccan dealers sell such specimens as Goethite when in reality they are black manganese oxides easily distinguished by a simple streak test.

Also, I believe that the Hematite shown in photo 500470 is from the Irhoud Mine, since such specimens are quite common at that mine. John S.

7th Aug 2013 21:53 UTCRock Currier Expert

Mibladen and Midelt are very near the base metal mines that have produced so many of the fine specimens of vanadenite, cerussite and baryte that have come out of Morocco over the years. There are no active commercial mines operating and all of the specimens now produced are dug by the locals from the abandoned mines in the area. However, sometimes specimen production at near by localities is a bit slow and the dealers and diggers fan out across Morocco and get specimens from where ever they can and bring them back to Midelt or Mibladen to sell. In other words, these two towns, well Mibladen is a village and a few Km away is the good size town of Midelt have become the place to go in Morocco if you want to get specimen, and even a lot of stuff not from the base metal mines nearby. You can sometimes even find stuff for sale that is not from Morocco at all. Some people buy things in Mibladen or Midelt and think that must be the locality that produced the specimens and put the name of those two towns on the labels.

12th Aug 2013 17:41 UTCKnut Edvard Larsen 🌟 Manager

I agree with John in that some of the photos labelled goethite from Taouz looks suspiciously like manganese oxides and not goethite or hematite.

Based on my observations and collecting at one of the many localities on the area, Vein 12, Tadaout see http://www.mindat.org/loc-245336.html

and Jahn et al. (2003): Marokko - Land der schönen Mineralien und Fossilien. Bode Verlag, Haltern, Germany, 543 pp
I can say that both hematite, manganese oxides and goethite does occur as collectible minerals at Vein 12.

Minerals found in this area is commonly labelled as Taouz, the nearest town (large village) in the area which does not produce minerals.

Here is a quick description:

Hematite

Occurs as typical kidney ore, similar to these: http://www.mindat.org/photo-237811.html and http://www.mindat.org/photo-320134.html. When found on the dump they apperar not as shiny as this specimen though: http://www.mindat.org/photo-480656.html; It was customary, I was told, that the specimens were improved by being heavily polished before offered for sale.

Btw, the samples we observed offered for sale at the mine, see examples in the attached photo, may of course have come from other sources, but they were quite similar in appearance to material that could be observed on the dumps.

Goethite

The most typical ones occurs as black stalactites and boytroidal masses. A cross-section of the stalactites or "spheres" will display a typically radiating, fibrous structure of darkbrownish crystals (which the manganese oxides does not). These are often forming a nice matrix for sharp, six-sided brownish or orange vanadiite crystals ( vanadinite also occurs on the manganes oxides matrix though)

some typical examples:

http://www.mindat.org/photo-217984.html, http://www.mindat.org/photo-188407.html, http://www.mindat.org/photo-87610.html

Manganes oxides.

These are more more greyish, softer and forming wartlike or cauliflower-like aggregates. Distinguishable layers of grades of grey may often be observed in the broken parts. Sometimes small cavities with shiny microcrystals of Mn-minerals (pyrolusite ? and others) may be observed in the matrix.

Some typical examples are : http://www.mindat.org/photo-503763.html ( note the cross-section of the broken "warts" in the left side of photo: with concentric greyish structure), http://www.mindat.org/photo-39914.html

Note: Some of the stalactites may also be consisting of consentric layers of both manganese oxides and goethite.

12th Aug 2013 17:49 UTCKnut Edvard Larsen 🌟 Manager

These are labelled as goethite, but looks more like manganese oxides :

http://www.mindat.org/photo-48630.html. Note small cavities with microcrystals of a shiny, probably a Mn-mineral and the concentric structure

http://www.mindat.org/photo-59686.html. Already mention by John above.

http://www.mindat.org/photo-88343.html and child, already mention by John above

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