Sample sources

Most of the samples were collected by David himself; they were organised into distinct "sub-collections according to country of origin, year of harvest, or other criteria. Some colleagues kindly offered him some samples they had collected themselves, and these have become additional sub-collections. David would also like to thank his 29 colleagues from different countries who donated samples to COSEM (289 in total) in order to increase the worldwide representativeness of this unique collection (see the list of collectors). All this information is compiled in a database in which the 2241 samples can be sorted in several ways. This database and all the samples have been donated to the Museum's Collections Department so that COSEM can become a State Collection and serve the scientific community as a reference on eclogites for centuries to come.

Extensive research, data acquisition and publications

The range of studies of the samples collected in COSEM is extremely varied. Many have been processed into thin sections. The most interesting rocks underwent more detailed analysis: chemical analysis of the overall rock by conventional wet chemistry or by X-ray fluorescence (XRF); mineral and/or crystallographic analysis by X-ray diffraction (XRD), analysis by electron microprobe (EMP), scanning electron microscope (SEM) or transmission electron microscope (TEM), Raman microscopy (MSR) and structure refinement (SREF); this last method was used in particular for the new mineral species discovered by David and/or his teammates.

The results of these studies were presented in David's two theses (SMITH 1968, 1976) and in numerous international scientific publications, book chapters, scientific journals and newspapers. There is also an abundance of "published abstracts", such as in TERRA COGNITA on the first conference in the series "International Eclogite Conferences" (IEC), of which David was one of the co-founders. This journal went on to establish the new journal TERRA ABSTRACTS, of which David was a founding editor. A full list of all these various publications is provided here in the Work list.

Unfortunately, many other research results acquired by David on the COSEM rocks have not been, and never will be, published, for lack of time and/or money. Also, many COSEM samples have never been analysed. Despite this, samples without analytical data have been kept within COSEM in order to provide a good collection of all the rock types that exist at the sampled locations. Rocks that, for one reason or another, were of less scientific interest have already been eliminated from COSEM.

New mineral species found

This collection contains a huge amount of mineral material to be exploited. Several new mineral species (e.g. nyböite, Mg- or Fe-aluminotaramite, lisetite), or others that are very rare in the mineral world, have already been discovered in COSEM rocks (see the list of new or rare species found in norwegian eclogites). These important discoveries, which have thus enriched the international catalogues of species recognised by the IMA (International Mineralogical Association), were acquired thanks to the exceptional chemical and geodynamic conditions (e.g. UHPM) of the Norwegian eclogite formation, but also to David's particular interest in crystallochemistry. There's nothing to say that there aren't other new mineral species to be discovered in this collection, just waiting to be found!

Types of rock collected

The COSEM includes different types of rock (jointly decided with the head of the MNHN Petrology Collections):

1 – High-pressure or ultra-high-pressure rocks with "eclogite" or "blue schist" metamorphic facies. These two facies correspond to pressures and temperatures where the plagioclase mineral is no longer stable; the main minerals are a sodium clinopyroxene rich in the jadeite pole and a magnesian garnet rich in the pyrope pole. These two species are often accompanied by quartz, cyanite or zoïsite. Orthopyroxene, a clinoamphibole such as glaucophane or nyböite and a mica such as paragonite, phengite or phlogopite may also coexist. Sometimes there are UHPM-indicating minerals such as coesite or diamond.

2 – Prograding or retrograde metamorphic rocksIn other words, formed before or after the peak of metamorphism during burial by subduction or during exhumation in a collision or Metamorphic Core Complex context, for example.

3 – The surrounding rocks. It is often the rocks known as 'gneiss' or 'schist' that, in the field, are generally found associated with eclogite 'lenses'. The origin and evolution of these non-eclogitic rocks are intimately linked with those of the eclogites, so it is essential to study them at the same time.

4 – Deep rocks often associated with eclogites in metamorphic terrains, such as anorthosites, granulites, metadolerites, metagabbros, dunites, peridotites, lherzolites, etc.

5 – Nodules of high-pressure or ultra-high-pressure rock in the Earth's mantle which are found in volcanic rocks or kimberlite diatremes (vertical channels from which mantle material has been rapidly brought to the surface). These 'host' rocks have upwelled fragments of heavier rock, including eclogites.

6- Special associated rocks which do not fall into the above classification but which outcrop in the vicinity of eclogites, blue schists or others and which may have played a role in the genesis of these high-pressure rocks. Here we include materials transformed or incorporated by injection or partial fusion: veins or pegmatites; or by compression: mylonites or pseudotachylites.

COSEM includes a majority of Norwegian rocks, as David Smith has focused his research on Norwegian eclogites. These rocks have proved to be very important scientifically because of the ultra-high pressures found there, the many new mineral species discovered there, and the very good exposure of the outcrops (little vegetation and good preservation).