Jean-Franck Charlet: “We find more and more crystals in the high mountains”

Initiated in the hunt for crystals from his adolescence, Jean-Franck Charlet is a guide to high mountain, but also crystal. This term designates not a profession, but a passion: that of going to pick the crystals exposed on the sides of mountains. “They are found in what are called ‘ovens’, open fissures in the rock lined with crystals, which have been freed by the erosion of the mountains”explains J.-F. Charlet.

These crystals are the result of 15 million years

As Jean-Franck Charlet explains, “These crystals were formed about 10 kilometers deep, 15 million years ago, during the collision between the African plate and the European plate. The collision brought up granite from the earth’s magma. During the collision, everything was compressed so strongly that cracks were created in the rock. Water then accumulated in these cracks, or rather a aqueous solution containing water, but also various minerals which are dissolved there. »

All these processes take place at very high pressure (400 times atmospheric pressure) and high temperature, about 500 degrees Celsius. The elements contained in the water are dispersed and dissolved in it atom per atom until the solution becomes saturated: “Little by little, the rock rises, about one millimeter per year, so what was 10 km underground 15 million years ago is today at the top of Mont Blanc: it is the natural process of formation of mountains. The temperature and the pressure decrease, then the water becomes supersaturated with elements and they then begin to precipitate. Added to the various compressions and decompressions that the rock undergoes during its ascent, the aqueous solution changes into crystals which then line the sides of the cavity”. Of course, this mechanism of formation of crystals is the basis for the formation of all minerals, and these depend on the composition of the source rock in which they were formed.

Then there are the conditions that accompany the ascent of the crystal who will make it as it is found today in the mountains. “There are two possible states for solid : the crystallized state, where the atoms form a regular lattice, and the state amorphous where everything is broken down. In the crystallized state the crystals are transparent. Then, the type of crystal is defined by the molecule base, it is she who will impose the structure of the atomic network: there are thus more than 3,000 different minerals! So for the quartz which is an oxide of siliconthe base molecule is a tetrahedron, and from it a six-sided hexagonal crystal is formed”continues Jean-Franck Charlet.

Jean-Franck Charlet hunts crystals all over the world, but with a particular appetite for Mont Blanc massif, in the Alps. Some groups of crystals can reach 50 kilograms part, which must then be descended from the high rock walls using ropes and then carried in your backpack. back through glaciers then steep paths. “Only the crystals found in the cracks opened by the natural and continuous erosion of the walls are authorized for harvesting”he explains.

But the most sought after in the region remains the pink fluorite which, as J.-F. Charlet mentions, is sometimes nicknamed “the gold of the crystal makers”. It’s a mineral much sought after by collectors and by crystal makers, because it is very rare in the world and the most beautiful samples come from the Mont-Blanc massif or central Switzerland which has the same geology. “In mineralogy, this is called the fever rose gold, because of the fluorite rose found in the Mont-Blanc massif and in Switzerland. It is a mineral highly sought after by collectors and crystal makers, as they are much more aesthetic than the smoky and opaque crystals characteristic of the region. »

Because the crystals found mainly around Mont Blanc have a somewhat special appearance: they have a color smoke, caused by radioactivity surrounding granite. “The internal radioactivity of the granite bombards the crystal and deforms the crystal lattice. The light rays that could pass through are then deflected, creating this smoky aspect characteristic of the Mont-Blanc massif. »

Global warming, particularly accentuated in the mountains, causes the gradual melting of glaciers

As the atmosphere warms more and more and faster and faster, Icebergs are melting. A process that gets worse when you go up in altitude. “Around 2,500 meters, we lose almost 10 meters of thickness per year, explains JF. Charlotte. For crystal seekers, this can be a boon, as acres of rocks that were previously hidden under the ice come to light, potentially unearthing new crystal furnaces. »

“There are more and morecollapses in the mountains. Climate change is strongly accentuated there, the physiognomy of the glaciers changes everywhere », worries J.-F. Charlet. In particular, in the Chamonix region where he is a high mountain guide, “the rocks forming the large walls are held together by age-old ice which serves as cement. When this ice melts, whole sections of walls can collapse, as happened recently at Les Drus, one of the most beautiful rock needles above Chamonix. »

Catastrophic scenarios could occur in the next 20 or 30 years, and even reach the valley depending on the evolution of temperatures. “We are therefore continuously monitoring the mountain: certain glaciers whose base has hitherto stuck to the rock could movement as soon as the ice in contact with the rock would begin to melt, potentially creating large avalanches. Thus scientists measure the temperature under certain glaciers, where we observe a continuous increase in temperatures. We also look at the altitude from which the rocks remain held in place by the ice all year round: what is called the permafrost – Where permafrost, in English. It was 3,400 meters 30 years ago, now we are more around 3,700, and it is only increasing”, alarm Jean-Franck Charlet.