César Menor-Salván and Olivier Pourret are the winners of the EAG Photo Contest 2014 and we have asked them tell us more about their photos and their passion…

“Destructive Beauty”: winning photo of the theme “The changing world: geochemistry in action”
The picture shows crystals of neoformed Epsomite (magnesium sulfate heptahydrate) in a wall of my own house, affected by “sulfate attack”. The sulfate attack is the alteration process of building materials by sulfate-rich rising damp, usually by groundwater infiltration. When I closely examined the strong damage that suffered the wall, I observed glittering crystals in the water front that was moving upward by capillarity. As my passions are the photomicrography and the mineralogy, I saw it as an opportunity to understand how the groundwater destroy the building materials. I thought that I had caught out in the act the process of formation of hydrated secondary phases by weathering of previous materials. Geochemistry in action in my own walls! The glittering crystals saw promising, and, indeed, under the stereomicroscope showed the beautiful landscape that I tried to capture in the micrography.

As expected, the Raman spectrum of the crystals shown in the photography, confirmed it as Epsomite. The magnesium sulfate reaches saturation in the ascending water and forms efflorescences and salty deposits (salitre in Spanish). In this case, the low temperature and stability of conditions favored the crystal growth. The crystallization of Epsomite, a highly hydrated mineral, provokes internal pressure in the materials, swelling, fractures and paint peeling. The Epsomite stability zone is very limited and, with decreasing relative humidity, it dehydrates forming Pentahydrite (also identified by Raman spectroscopy), that forms white, dull pseudomorphs after Epsomite. Further dehydration converts the crystals in a white powder. The dehydration leads to shrinking and collapse of the building material.

The saturated sulfate solutions react with materials as concrete, forming other secondary phases, as the thin acicular crystals in the lower right corner of the picture, identified as Thaumasite. The reaction between sulfate-rich infiltrating solutions and the calcium silicates and aluminates in the concrete, lead to the formation of Ettringite and Thaumasite, provoking flacking and softening of the concrete and consequent collapse of the structures.

Despite of the losses associated with the destruction of building materials, I could not resist the temptation to show the inner beauty of the process: beauty contained in the transformation of materials and formation of new minerals, and the aesthetic impression of the crystals. This is the beauty of Nature, that remind us that all of our creations, civilizations and cultures, futile attempts to transcend, are weak, impermanent and subject to the laws of Geochemistry, that is, the law of constant flow and change. This beauty (conceptual and aesthetic), sometimes hidden to our naked eyes, but always present in Nature and our laboratories, drives my interest in the photomicrography. My routine equipment consist in a Nikon Coolpix camera attached to the phototube of a Zeiss Discovery V8 microscope. The picture is the result of layer composition of 10 frames. Field of view is 2 mm.