Catch a falling star: the strange story of the Tocopilla Meteorite

Think ‘meteorites’ and think ‘art’ and the average human mind will probably conjure up the garish and probably fantastical cover of a sci-fi novel depicting colliding worlds in shades of pink and blue or alternatively an ‘artist’s impression’ of the late heavy bombardment or the precise moment of the Chicxulub impact. Think again.

Tate Britain is hosting a major retrospective of German artist Sigmar Polke’s (1941-2010) work, which is due to end this Sunday (8th February 2015; Herbreich et al., 2014). If you’re in London you should go and see it. Polke’s work spans decades and genres which at first present no surprises; 1960s Pop Art, for the 1970s, magic mushrooms and sex. And then you walk into rooms with a startling explosion of creativity influenced by Polke’s use of materials from the 1980s onwards. Here we find canvases glittering with mica, a large painting depicting a lump of gold ‘Goldklumpen’ (1982) painted with poisonous pigments orpiment and realgar (arsenic sulphides) and green copper arsenite pigments (Schweinfurt Green). Polke also experimented with even more dangerous substances such as uranium based pigments (i.e. Uranium [Pink], 1992); His intention here was to render his art more ‘harmful’.

Polke continuously experimented with materials. He became interested in ancient and traditional painting materials, even producing his own Tyrian purple extracted from seashells (with minor success) to create the painting Purpur (1986). He was also fascinated with modern pigments with interesting optical effects, predominantly composed of synthetic micas coated with thin layers of metal oxides. These included iridescent and metallic car paints and ‘Magic Purple’; the latter having the effect of appearing purple from one angle and then golden from another – this effect could be optimised by burnishing the painted surface, producing rather beautiful paintings including the triptych Negative Value I, II and III (1982).

Polke was fully cogniscent of the fact that many of his paintings would decay and would be beyond the help of the most skilled of painting conservators. He knew that his materials were difficult and would change over time. For example, the orange arsenic sulphide pigment realgar on Goldklumpen has altered to a yellow shade, indistinguishable from the orpiment. However that is not necessarily always going to be the case. One of his ‘pigments’ has remained unchanged for over 4 billion years, however this fact would not help any future forensic analyst of his paintings identify it.

In 1988 Polke produced asigpol006 series of five works entitled ‘The spirits that lend strength are invisible I-V’. Inspired by the ancient land and native peoples of America (Garrels, 2010), these works used a variety of materials and media, including powdered nickel, silver leaf and silver oxides, artificial resins and even Neolithic stone tools (in V, left). Perhaps most striking in terms of materiality is ‘The spirits that lend strength are invisible II’ which is a scatter of powdered meteorite dust dispersed onto artificial resin. This painting, currently on tour with the exhibition Alibis: Sigmar Polke 1963-2010 belongs to The Doris and Donald Fisher Collection.

polke meteorPolke used 1 kg of powdered Tocopilla meteorite to create this painting (right) which is somehow reminiscent of Palaeolithic cave art. Luckily Polke’s use of this material is well documented, otherwise for someone like me, who, perhaps a century from now, will be characterising the pigments used in late 20th Century art, this would come as an unexpected and unrecognisable surprise. It is an extra-terrestrial encounter with unfamiliar materials not found on Earth, except when delivered my meteorites.

The Tocopilla meteorite is one of many associated with the same bolide that was found in 1875 in the Antofagasta region of northern Chile. It exploded in the air before impact and 266 kg have subsequently been collected from a large area of which Tocopilla is just one locality. The find is now known collectively as North Chile (Grady, 2000) and the various and many fragments found have been shown to be chemically identical. Chemically, this is an iron meteorite, probably representing the core of a small planet that was smashed to bits during the early history of the Solar System. More specifically it belongs to a class of meteorites known as hexahedrites and predominantly composed of the iron-nickel alloy kamacite. These are iron-rich meteorites with only approximately 5-6% nickel present. It also contains 3400 parts per billion of the element iridium, which puts in in a class of hexahedrite meteorites known as IIAB (see Morgan et al., 1995).

Just what might a 22nd Century pigment analyst expect to find in this painting? Axon & Nasir (1982) analysed a sample of the 2.5 kg Tocopilla mass owned by the British Museum (now the Natural History Museum). They found that the main mineral kamacite formed large crystals composed of 94.51% iron, 5.05% nickel with a trace of cobalt (0.4%). Enclosed within these crystals were lath- or needle-shaped inclusions of another mineral called schreibersite, an iron-nickel phosphide, (Fe, Ni)3P. Schriebersite is brittle and the needle-shaped crystals form planar features known as ‘rhabdites’ along which the meteorite broke up into its many fragments. Nolze et al. (2006) found tiny inclusions of the chrome-nickel mineral carlsbergite in the schreibersite crystals. Also present are small, massive crystals composed of lamellae of extra-terrestrial sulphide minerals troilite (FeS) and daubréelite (FeCr2S4). None of these minerals would be encountered in terrestrial rocks. Iron does not occur native (even in alloys) naturally on our wet, oxygen-rich planet and although the iron sulphide pyrite (FeS2) is common on Earth, troilite is unknown from terrestrial sources.

SchreibersiteLeft, needles of schreibersite, included in kamacite, radiate out from an iron sulphide-rich grain. This image is adapted from Axon & Nasir (1982). The field of view is about 1 mm across.

Meteoritic material is in the majority ancient. With the exception of rare meteorites know to have been derived from either the Moon or Mars, the vast majority of meteorites solidified in the primordial Solar System. Morgan et al. (1995) used the rhenium-osmium geochronometer to calculate the age of the Tocopilla meteorite and others of similar composition. They found that it is the age of the earliest material known in our Solar System, over four and a half billion years old (4.5 Ga)., over a million years older than the oldest known minerals on Earth. Most meteorites sit in museums or museum archives or are bought and sold by collectors, but at least a part of the Tocopilla meteorite will endure in a most unexpected way on the walls of art galleries. Many casual observers would not know that ‘The spirits that lend strength are invisible II’ is constructed from a material older than our planet. Polke would have known this and therefore his painting’s resonance with deep time, almost beyond imagination. I think this would have satisfied him. Polke created an unique painting with a unique material legacy and one that takes materiality in art to new extremes.

Links & References

You can see some of Polke’s work on the MoMA website here http://www.contemporaryartdaily.com/2014/07/sigmar-polke-at-moma/

Tate http://www.tate.org.uk/whats-on/tate-modern/exhibition/alibis-sigmar-polke-1963-2010

Image: The spirits that lend strength are invisible II http://superficiecontextual.blogspot.co.uk/2009_07_01_archive.html

Image: The spirits that lend strength are invisible V http://shop.tate.org.uk/alibis-sigmar-polke-19632010/polke-the-spirits-that-lend-strength-are-invisible-v-custom-prints/invt/sigpol006

Axon, H. J. & Nasir, M. J., 1982, A microprobe study of Ni-Co distribution about a schreibersite body in the Tocopilla mass of the North Chile hexahedrite [BM 1931,13]., Mineralogical Magazine, 45, 283-284.

Garrells, G., 2010, http://www.sfmoma.org/explore/multimedia/audio/103

Grady, M. M., 2000, Catalogue of Meteorites: 5th Edition., Cambridge University Press. p. 371.

Halbreich, K., Godfrey, M., Tattersall, L. & Schaefer, M. (Eds.), 2014, Alibis: Sigmar Polke 1963-2010., Tate Publishing, London., 317 pp.

Morgan, J. W., Horan, M. F., Walker, R. J. & Grossman, J. N., 1995, Rhenium-osmium concentration and isotope systematics in group IIAB iron meteorites., Geochimica et Cosmochimica Acta., 59 (11), 2331-2344.

©Ruth Siddall 2015

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About Ruth Siddall

Geologist, geoarchaeologist and co-author of The Pigment Compendium. Follow @R_Siddall; Facebook|Cultural & Urban Geology
This entry was posted in Art, Artists' Pigments, Materiality, Meteorites, Minerals, Pigments and tagged , , , , . Bookmark the permalink.

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