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Fossil Fish blog

2 Posts tagged with the mineralogy tag
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Our last day in the field was one our Ore Curator, Helena Toman, was particulary looking forward to. We had finished visiting the fossil sites and today we would spend having a look around an active mine and collecting samples for the Museum's collections.

 

Helena tells us more about it...

 

Before we delve into the world of ores, it’s probably best to clarify what an ore actually is! An ore is any naturally-occurring mineral or assemblage of minerals from which economically important constituents, particularly metals, can be extracted. The field of economic geology focuses on ore deposit formation, ore mineral exploration and the successful extraction and processing of an ore. I like to think of economic geology as occupying one of those crucial interfaces between science and society and so one of the challenges as the Ore Collections Curator is to make the science accessible to society.

 

Over the past couple of months, you’ve taken part in our adventure to the geological treasure trove that is Morocco. After sieving for Cretaceous sharks teeth; excavating extinct volcanoes for mantle xenoliths and exploring for minerals we reach the final field stop of this incredible journey, the cobalt-nickel arsenide ore bodies of Bou-Azzer.

 

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On the road into Bou-Azzer mine.

 

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Looking over the mine.

 

Located in the central Anti-Atlas Mountain range within a very old (788 ± 9 Ma, Gahlan et al., 2006) ophiolite – a section of the ancient sea floor that has been obducted onto land - Bou-Azzer is presently the only mining district in the world to produce cobalt as a primary commodity from arsenide ores (USGS, 2011).  As cobalt is usually extracted as a by-product, mineralisation at Bou-Azzer is unusual and therefore scientifically interesting. Put bluntly, we’d be mad not to visit and collect!

 

One thing that you can safely predict is that most mining operations are located in very remote and difficult-to-access locations. Bou-Azzer is no exception. After a long, bumpy, but visually stunning car ride we were warmly welcomed by mine employees who introduced the group to the geology and mining history of the district. Then, after a much needed sugary mint tea, the moment had arrived. The moment I had been waiting for – access to the ore pile! We drove up. The midday sun beat down on the mass pile of rocks before us.

 

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Looking through the discarded material next to the mine.

 

Dull silvers highlighted the primary cobalt mineralisation of Bou-Azzer: skutterudite (CoAs); safflorite (CoAs2); loellingite (FeAs); nickeline (NiAs) and rammelsbergite (NiAs2) while pale pinks and rich purples drew attention to the secondary mineral, erythrite (Co3[AsO4]2.8H2O) (Ahmed et al., 2009). I have to admit, as ores go, they rarely get ‘prettier’.

 

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Some of the samples we collected at the mine.

 

While I could have stayed for days, our schedule was very tight and it wasn’t long before we needed to leave; it really was a case of ‘all hands on deck!’ Decision making (often against the clock) is part of a curator’s in-field skill set, so only samples that best provided an understanding of the mineralogy, mineral assemblages, mineral textures and mineralisation styles present at Bou-Azzer, made it into the suite.

 

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Primary cobalt ore.

 

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Primary cobalt ore.

 

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Secondary erythrite.

 

This suite (of 30 hand samples) was collected with two purposes in mind:

 

     1) collection enhancement of the existing Natural History Museum ore collection

     2) to serve as material for research initiatives investigating cobalt as a ‘critical element’

 

As someone whose scientific interest area is economic geology, visiting Bou-Azzer was the cherry on top of the cake – or, as we are dealing with all things Moroccan, the mint in my tea. Describe the fieldtrip in one word? Ore-some.

 

If you would like to find out more about ores, the Museum ore collection and our research, please see our ores group webpages, or you can follow up with the references below.

 

 

Thank you to Helena for telling us more about the ores and what we collected.

 

I was particularly excited about going to the mine as we were trying to find some pink minerals, and pink is my favourite colour. Some of the specimens looked wonderful sparkling in the sun and it was great that we were able to collect so many new samples for the ore collections.

 

I thoroughly enjoyed my time in Morocco, seeing something new every day and you can learn so much more in the field than reading a book or paper about the area. For me, it was great to learn from the mineralogists on the trip and find out more about what they do and also learn from more senior members of staff (I think we all enjoyed learning from each other and getting to know each other better).

 

Being able to visit sites I have heard so much about such as the Kem Kem and Goulmima was fantastic. And knowing that finding the fossils (and mineral specimens) during our trip helped to enhance the Museum collections is a great feeling. I am hoping to return to Morocco later in the year to present some results at a conference of specimens we collected during our trip.

 

References

 

Ahmad, A.H., Arai, Shoji, and Ikenne, Moha, 2009, Mineralogy and paragenesis of the Co-Ni arsenide ores of Bou Azzer, Anti-Atlas, Morocco: Economic Geology, v. 104, no. 2, March–April, p. 249–266.

USGS, 2011, Minerals Yearbook: Morocco and Western Sahara (Advanced Release), p. 30.1 – 30.9.

Gahlan, H., Arai, S., Ahmed, A.H., Ishida, Y., Abdel-Aziz, Y.M., and Rahimi, A., 2006, Origin of magnetite veins in serpentinite from the Late Proterozoic Bou-Azzer ophiolite, Anti-Atlas, Morocco: An implication for mobility of iron during serpentinization: Journal of African Earth Sciences, v. 46, p.318–330.

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As I mentioned on my Twitter account @NHM_FossilFish, myself and several colleagues from the Museum and another institutions recently went on a collections-enhancing trip to Morocco. It was absolutely amazing! Over several blog posts myself and Zoe Hughes will take you through our adventures, so make sure you check out her Brachiopod and Cephalopod collections blog!

 

Over the last few years lots of fossils and minerals from Morocco have flooded the market. We are even seeing an increase in people bringing them to events for us to identify. Currently our collections from Morocco are limited, so during the trip we wanted to:

  • expand the Museum's collections
  • see famous sites like the Kem Kem (famous for dinosaurs) and Goulmimia (famous for ammonites and fish)
  • collect some of our own samples

 

Over the last year the Museum's former Palaeontology and Mineralogy Departments merged to form the new Department of Earth Sciences, and because both minerals and fossils from Morocco are of interest to the wider scientific community we mounted our first earth sciences fieldtrip

 

The palaeontologists of the group were myself, Martin Munt, Martha Richter, Zerina Johanson, Zoe Hughes, Mark Graham our fossil preparator, research associate David Ward and regular Fossil Fish visitor Charlie Underwood from Birkbeck, University of London. The mineralogists were Mike Rumsey, Helena Tolman and analytical chemist Emma Humphreys-Williams.

 

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Back row: Mark Graham, Zerina Johanson, Martin Munt, Charlie Underwood, David Ward, Martha Richter, Mike Rumsey, Helena Toman and Emma Humphreys-Williams. Front row: Myself (Emma Bernard), Moha (our guide) and Zoe Hughes.

 

On Wednesday 18 September our group arrived at Heathrow Airport for our flight out to Casablanca, Morocco. We arrived late at night and were met by our drivers and our guide Moha. We went straight to the hotel and settled in for the evening ready for our first day in the field.

 

On Thursday 19 we were all up ready for a trip to a farm near the town of Oued Zem. This area is known for the phosphate mining industry, a by-product of which is fossil material, specifically Cretaceous reptiles such as mosasurs and thousands upon thousands of shark teeth!

 

It was a warm day, about 30 degrees and not a cloud in the sky. We went to a farm where Charlie and David had previously collected samples and have a good relationship with the owners. Here we wanted to sample different beds to see what sharks and other marine animals were present in each layer.

 

We collected large samples and them put them through several fine sieves and then picked out what fossils we could find. This mainly consisted of shark and ray teeth and small fish bones. We collected over 20 bags of this sediment to bring back to the Museum so we can have a closer look.

 

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Charlie Underwood digging in the rock face and sieving for shark teeth.

 

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Emma and Zoe enjoying the sun and picking the sediment for shark teeth.

 

For lunch we went to another local farm where I think we all agreed, we had one of the best tagines any of us have every had. It was delicious. The farm also had a fossil shop and it was great to look around at what they had on offer.

 

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Just some of the fossil specimens on offer in a Moroccan farm shop.

 

In the afternoon we were back at the farm with all the shark teeth and we were in for a real treat. Part of their land included an old phosphate mine which they now use for excavating fossils, and inside there was a near complete shark belonging to the genus Otodus of Yspresian age (Early Eocene in age, about 50 million years old). Shark skeletal material is cartilaginous and therefore rarely fossilised, but this specimen has several articulated vertebrae and lots of teeth preserved.

 

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All set and ready to go down the mine.

 

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Me with the shark skeleton, the round white circles are the vertebrae.

 

The mine was a lot cooler inside than outside which made for a nice change when we were still adjusting to the temperature difference. After we stumbled back outside we were greeted with some lovely saffron tea (a first for me) and we packed all our specimens and sediment into the van and headed off for the hotel discussing what we had found that day.

 

From here on, myself and Zoe Hughes will be taking each day in the field in turn, so make sure to check back to find out what else we did...