Lapis Lazuli, Sacrebleu!

Will Gray
Saturday 27 June 2015

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My research so far has been somewhat hindered by the fact that my samples have not yet arrived from America! They were purchased in a physic/palm-reading shop in Los Angeles, where my supervisor learned that lapis lazuli is a ‘gateway-stone’ to palm reading… Clients are tempted in with the promise of pretty stones – no, really! So since the middle of June I’ve been gathering as much data as I can from the relatively limited amount of available literature, most of which dates from the 1970s. The lack of literature is slightly intimidating, but also exciting as I now have the opportunity to use modern instruments and techniques to answer many of the remaining questions surrounding this beautiful gemstone.

Since antiquity, the gemstone lapis lazuli has been admired for its remarkable blue colour. When ground into a powder it becomes the pigment ultramarine, most commonly used in Renaissance depictions of the Virgin Mary. Its principal source is located in the mountainous Badakhshan region of northern Afghanistan, although there are also important deposits in Russia and South America. I am mainly looking at material from Afghanistan.

Lapis lazuli is thought to form during contact metamorphism of limestones and meta-evaporites. The conditions of this metamorphism are almost entirely unknown and uncovering them is the main focus of my research. The formation of lapis lazuli likely involves hydrothermal fluids, and I should be able to deduce the temperature, chemistry and origin of these fluids by examining the ways different elements are partitioned between the minerals lazurite, pyrite and pyrrhotite.

So why does all this matter? Well the knowledge gained during my research could potentially be of use to economic geologists. The rock types that host lapis lazuli can contain valuable metal ores in deposits elsewhere in the world. It could also be used to determine the provenance of historical artefacts, perhaps shedding light on ancient trade routes. At least that’s what I’m hoping for!

My project involves a significant amount of self-leadership, and looking forward I know that the experience will prepare me well for my dissertation and all the challenges next year will bring.

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