Curators at the Museum receive donations or offers of donations of new specimens on a regular basis. An interesting rock made almost entirely of microfossils arrived from Brazil a couple of weeks ago. We have not officially accepted this donation yet, but this is an interesting acquisition story about an interesting specimen.

The rock specimen offered for us as a donation

The donor Prof. Dr. José Luiz Lorenz Silva offered the specimen to us following his publication on a rock called a spongillite which was found at Très Logoas in the State of Matto Grosso do Sul, Brazil. This rock was deposited in the Late Pleistocene period about 37,000 years ago in a freshwater pond. The microfossils contained suggest that the climatic conditions were colder at that time and that it was deposited in a slightly acidic peat bog pond.

Following the donation, my Erasmus student Angelo Mossoni and I placed a fragment of the rock under the scanning electron microscope to see what it contained. The rock is very light as it is composed almost completely of the siliceous remains of sponges and diatoms. Diatoms are algae that secrete a characteristic shell wall or frustrule of silica. They can be found in the fossil record as far back as the Jurassic period and are commonly used in the present day as indicators of water quality.

A scanning electron microscope image of part of the rock showing the remains of thousands of diatoms

At the start I mentioned that we had not officially acquired this specimen. All future donations are carefully scrutinised so that we are sure that the material has been donated to us without contravening laws of the country that it was collected from. Brazilian law states that specimens cannot be collected from their country and sent abroad unless relevant agreements exist between the institutions in Brazil and the institutions accepting the donations.

To account for this, we have registered the specimen as "Object Entry". This means that we are not certain just yet if we have the correct paperwork and agreements in place to accept it and acknowledge that we do not officially hold title to its ownership. Specimens sent to us for identification or specimens belonging to other institutions but being studied here are commonly registered here as "Object Entry" until they are returned to their owners.

Some more diatoms under the scanning electron microscope. The scale on the picture is 10 microns which is 0.001 of a millimetre.

As you can see from the scanning electron microscope images above, it is certainly a very interesting rock. Museum policy on acquisition states that we will seek to acquire specimens if one of the following is satisfied: it helps to bridge or fill gaps in collections, it fulfills a research need, it complements existing specimens in our collection, it has potential for public education or display, it is scientifically or historically significant.

The spongillite certainly covers several of these criteria and may well be of interest to the research of scientists in the Botany Department studying diatoms. My colleague Martha Richter is currently in Brazil and will be checking if the documentation we have is acceptable. Until we are sure, this very interesting rock specimen won't officially be making its way into our collections just yet.

The Erasmus Programme is European Union funded and enables higher education students in 31 European countries to study for part of their degree in another country. This is exactly what Italian Geology student Angelo Mossoni is doing here at the Museum this summer as part of his masters degree at Cagliari University.

Angelo working in the Micropalaeontology Laboratory

Angelo contacted me in early 2011 asking if I had any projects that I needed doing on conodont microfossils. Conodonts are the teeth of an extinct worm-like organism that are used widely for investigating the age of rocks between 200-500 million years old. This sort of information is very useful for oil or mineral exploration companies as well as for revealing the geological history of rock formations.

Finding conodonts can be a long process. The first stage is to dissolve in vinegar, limestones or other rocks that were deposited in shallow to deep seas. This produces large residues of microscopic fragments less than a millimetre in size that need to be examined under a microscope. I had already dissolved tens of kilogrammes of limestones from Oman so Angelo's first task was to help examine the residues.

Angelo has previous experience of this type of work but has not used separating techniques to reduce the size of the residue needing to be examined. He was introduced to a method using a heavy liquid sodium polytungstate that concentrates the heavier fractions of the residues that include the conodont microfossils. This means that less time is needed to examine the results under a microscope, a process that can sometimes take weeks or even months.

Adding residues to the heavy liquid sodium polytungstate

The heavy fraction then needs to be examined under the microscope and a fine paint brush used to transfer the conodonts into a separate cavity slide for further examination. Angelo and I then worked together to choose which specimens should be illustrated. Angelo was then taught to use the Axiocam Imaging System to take good publication quality colour images of the best specimens that he found (see below).

One of the conodont specimens found by Angelo. It is just over a millimetre in length.

The very best specimens were also illustrated using a scanning electron microscope so that the conodonts we found could be classified and used to provide a geological age for the sample. Precise dating of rocks from Oman is potentially of interest to oil companies in this region. Angelo found many other interesting fragments of fish and microfossils that will be published along with the conodonts in the future.

Studying some microscopic fish remains on the scanning electron microscope

Part of the strategic plan for the Museum is to 'provide a unique and personalised experience for learners, through engagement with real science, scientists and specimens'. We have certainly done this by teaching Angelo new techniques in the study of conodonts while he helps with a research project that has significantly enhanced our collections. More importantly we have enabled Angelo to achieve some of the goals of the Erasmus Programme by experiencing study in a laboratory away from is own country and greatly improving his English.

Angelo leaves at the end of August but that will not be the end of his association with the Museum. During his stay he has found many interesting new specimens that we will eventually publish together. Hopefully this will also be a great help to him in his future career as a micropalaeontologist. He has certainly done a large amount of very useful work during his time here for which I am very grateful.