Quick Links : Mindat手册 The Rock H. Currier Digital Library Mindat Newsletter [Free Download]

主页关于 Mindat Mindat手册 Mindat的历史版权 Who We Are 联系我们于 Mindat.org刊登广告

捐赠给 Mindat Corporate Sponsorship 赞助板页已赞助的板页在 Mindat刊登广告的广告商于 Mindat.org刊登广告

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

搜索矿物的性质搜索矿物的化学 Advanced Locality Search 随意显示任何一种矿物 Random Locality 使用minID搜索邻近产地 Search Articles 搜索词汇表更多搜索选项

Mindat手册添加新照片 Rate Photos 产区编辑报告 Coordinate Completion Report 添加词汇表项目

Mining Companies 统计会员列表 Mineral Museums Clubs & Organizations 矿物展及活动 The Mindat目录表设备设置 The Mineral Quiz

照片搜索 Photo Galleries Search by Color 今天最新的照片昨天最新的照片用户照片相集过去每日精选照片相集 Photography

Discussions

💬 Home 🔎 Search 📅 Latest

╳Discussions

💬 Home 🔎 Search 📅 Latest

Groups

Recent Images in Discussions

PhotosPoldervaartite - Wessels Mine, Hotazel, Kalahari manganese fields, Northern Cape Province, South Africa

29th Nov 2012 02:44 UTCEvan Johnson

Olmiite

Wessels Mine, Joe Morolong Local Municipality, John Taolo Gaetsewe District Municipality, Northern Cape, South Africa

Inevitably- didn't see any comments to this effect- is this analysed poldervaartite and not olmiite? Not to hassle anyone, just curious.

Best,

EMJ

29th Nov 2012 09:44 UTCUwe Kolitsch Manager

Fixed.

29th Nov 2012 09:46 UTCLefteris Rantos Expert

The photo shows typical habit of one of the original finds of Poldervaartite. As far as I know, such specimens have been confirmed as true Poldervaartite and not Olmiite. Of course, analytical confirmation is always a good thing in such tricky cases.

The same (i.e. apparently true Poldervaartite) also applies to photos 174151, 16977, 32828, 122374, 285174, 288014, 453861 and 491301 from the Poldervaartite gallery.

See also http://rruff.info/polder/display=default/ apparently a specimen from the same occurrence as http://www.mindat.org/photo-32828.html and http://www.mindat.org/photo-491301.html

On the other hand, photos 225669, 225671, 225670 and 225672 show typical Olmiite (associated with acicular Bulfonteinite) from more recent finds.

Lefteris.

29th Nov 2012 09:49 UTCLefteris Rantos Expert

Uwe, I'm not sure the edit was correct - I just noticed it now. As explained above, judging from the habit I tend to believe this is from older finds of true Poldervaartite.

At any case, it should be safer to rename Olmiite-Poldervaartite series.

Lefteris.

29th Nov 2012 10:12 UTCPierre Rondelez

Lefteris,

You mention:
The photo shows typical habit of one of the original finds of Poldervaartite

in fact I have seen many, many similar olmiites from very recent finds in N'Chwaning II and II.

I have some very good ones, just like the POTD-photo in my collection, they all come from N'Chwaning !!

Poldervaartite is a VERY rare mineral and the chances that you ever encounter one is are VERY small.

Without analysis it is the safest bet by far to id. them as olmiite.

Pierre

29th Nov 2012 10:36 UTCLefteris Rantos Expert

Pierre, I wasn't arguing on the rarity of true Poldervaartite. I was just implying that this one was probably one of these few, based on previous photos of original "Poldervaartite" I had seen, even before the recent finds that produced the new mineral Olmiite were made.

However, I just noticed the older thread you pointed out http://www.mindat.org/mesg-7-104499.html , stating that even some of the old "Poldervaartites", i.e. from the finds before the new Olmiite finds, were actually Mn-dominant.

So I stand corrected. I agree the safest thing is to rename as Olmiite, unless there is firm analytical evidence of the contrary.

Lefteris.

29th Nov 2012 17:52 UTCReiner Mielke Expert

Surely there must be someone out there with a photo of a confirmed poldervaartite that they can post on Mindat? However, even though none of the photos of "poldervaartite" on Mindat have been analyzed if they do indeed look like Poldervaartite it would be usefull to leave them as poldervaartite so that a collector knows which specimens are worth while analyzing in order to find poldervaartite. In otherwords it would save time and money not analyzing specimens that have no chance of being poldervaartite based on their appearance. Assuming appearance in this case is a guide.

29th Nov 2012 18:06 UTCAlfredo Petrov Manager

What if there isn't any real "poldervaartite" in the world, and it's all olmiite? I don't see any chemistry on the RRUFF Poldervaartite page, which was apparently just "confirmed" by x-ray.

8th Nov 2022 10:25 UTCDemetrius Pohl Expert

Around 1986, when, as a curator for the AMNH, I attended Geocongress '86 in South Africa. After the Congress I visited Ludi von Bezing in Upington to see his encyclopaedic collection of Kalahari Manganese Field minerals. He showed me a small number of specimens of creamy, very pale pink crystals in small groups and sprays, some on matrix which he had never seen before, as well as a fragment of a bright blue, glassy crystal, both from the Wessels mine. I took a small specimen of each back to the AMNH, where PXRD suggested both were new minerals. The creamy mineral became poldervaartite (Dai and Harlow, 1993) and the blue one, vonbezingite (Dai and Harlow 1992). The poldervaartite holotype specimen does contain some manganese, probably causing the pale creamy pink color. So, yes, poldervaartite does exist.

29th Nov 2012 18:32 UTCLefteris Rantos Expert

Poldervaartite does exist, although it's very rare. See http://www.mindat.org/mesg-7-104499.html

And apparently it exists both as zones within zoned Poldervaartite-Olmiite xls, as well as very pure end-member colourless xls, as described by A. Kasatkin.

Lefteris.

29th Nov 2012 18:48 UTCJeff Weissman Expert

Here is an image, taken in 1999, from a Mark Feinglos deaquisition - could this be from the original find of poldervaartite?

Scan from slide film, originally made with inadequate lighting

29th Nov 2012 18:52 UTCPierre Rondelez

By the way:

In the poldervaartite formula here on Mindat there is no sign of Mn ?

http://www.mindat.org/min-3252.html

When according to the Handbook of Mineralogy it should be:

(Ca;Mn2+)2(SiO3OH)(OH)

Clearly something to be looked at,

Pierre

29th Nov 2012 18:55 UTCAnatoly Kasatkin

Yes, as already noted in a thread of 3 years ago, I can confirm the real poldervaartite in Bill Pinch collection (ex-Clive Queit).

I am talking about this sample: http://rruff.info/polderv/display=default/

As Alfredo said, there is indeed no chemistry on RRUFF page, however, the fragment from that sample that Bill gave me, showed the following composition:

Ca1.00 (Ca0.78 Mn0.21 Fe0.01)1.00 (OH)

A very convincing poldervaartite!

29th Nov 2012 18:57 UTCAlfredo Petrov Manager

Pierre, the formula on Mindat is the end-member formula. A case could be made for including substituting elements, but then many hundreds of formulae could/should be changed. The danger lies in giving people the false impression that the substituting element must be present.

29th Nov 2012 22:38 UTCLefteris Rantos Expert

These two appear to be the same material as the Bill Pinch specimen analyzed by Anatoly: http://www.mindat.org/photo-32828.html http://www.mindat.org/photo-491301.html

30th Nov 2012 09:55 UTCPierre Rondelez

Yes Lefteris,

I agree but so does this:

http://www.mindat.org/photo-368061.html

Analysis has been done on this specimen and turned out clearly: olmiite.........

By the way: olmiite has a very large variety of forms and/or colours, 2 examples here:

http://www.mindat.org/photo-412193.html

and

http://www.mindat.org/photo-451392.html

you see, not exactly an easy mineral to recognize (sometimes) but what an interesting one.

Pierre

8th Nov 2022 10:37 UTCDemetrius Pohl Expert

One more note about poldervaartite. The original type-material was collected by Pieter de Bruyn, a miner living in Hotazel and working in the Wessels mine. Ludi von Bezing acquired the holotype specimen from Pieter. In 1996, after I had left the AMNH to work in industr in South Africa, I was able to acquire a co-type specimen from Ludi von Bezing.

Go to top of page