AH STUDIO | AQUAMARINE | # 1
January 2019
PHYSIS
n, the principle of growth or change in nature; the philosophical concept of growing and becoming
Photography as a practice is highly technical, and image creation is a constant toggle between the raw capture, now stored digitally, and its printing. What begins as light capture results in an object that is very sensitive to light and fades over time, so I am always thinking about colour in abstract way.
That the earth’s crust is so rich with hidden colour is of deep fascination to me, but the toxic nature of how we extract these natural resources is of increasing debate. Happily, aquamarine mining has a low environmental impact and no toxic chemicals are used. Literally meaning ‘sea water’, this gemstone from the beryl family possesses all the different shades of sea water from light blue to rich teal…but unlike water, the larger the gem the lower its saturation in colour.
What colour we see is determined by the underlying structure of things: how the elements that make up a material bond together determines the refraction of light and therefore colours we see. With aquamarine, this variety occurs is because of its specific hexagonal crystal system, which means the gem grows in columns that act like channels. So the micro reflects the macro, rivulets within rivulets. At a microscopic level an infinite variety of ions, neutral atoms, and molecules are incorporated into the crystal which give rise to the variety of colours that can be found, but it also mimics the way sea water changes colour.
Beryl crystal structure
Interestingly, increasing alkali content causes increases to the refractive indices and birefringence. What this means is that the more alkaline the crystal is, the more it shines.
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Looking more closely, I discover that a sensitivity to heat and light is also true of aquamarine. It is a gem that is deeply susceptible to colour changes both above and beneath the ground, related to its iron (Fe) content. Its uniquely tropical watery hue is attributed to Fe2+. Fe3+ ions produce a golden-yellow colour, and when both Fe2+ and Fe3+ are present, this shifts the structure to reflect more blue light. This darkest version of aquamarine is called maxixe, commonly found in Madagascar, but its colour fades to white when exposed to sunlight or is subjected to heat treatment, and only when irradiated does the blue return.
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And this last point is of particular interest to me, because increasingly gemologists are heat treating aquamarines. Why? Because our perception and preference for colour changes over time. Once prized for its naturally pale sea-green, there is now a consumer preference for sky blue (and I wonder is this possibly a confusion). Today, aquamarines are heated at low temperatures of about 400C to improve their colour... To me it feels like enhancing the sky at the expense of the sun. Whilst this procedure is legal and acknowledged by the CIBJO, in most cases it is almost impossible to know whether the gem has been heat treated or not... Having seen the plethora of wondrous natural colours this stone has to offer, I find it as disheartening as the melting icebergs. Why is the artificial promoted over the natural, the enhanced over the real?
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