An infinity of shapes, a multitude of colours and lights!
The collection of minerals presented in the « Treasures of the Earth » exhibition is remarkable for its shapes and colours. It sheds light on the formation of crystals and the origin of their diversity in nature.
Environmental forces
For the same chemical composition, a solid will crystallise in many different ways depending on the depth of its formation in the earth's crust, the temperature and pressure prevailing at the site of its formation, the abundance and nature of the fluids from which it is formed, and the space available for it to grow. The influence of some of these mechanisms is presented in an animated film.
Crystal lattices
The structure of a crystal is determined by an equilibrium point between the diameter of its atoms and their electrical charges. The result is an essential feature, known as symmetry, which in turn defines the way the atoms assemble into crystalline lattices. Among the most astonishing specimens you will find in our collections are twenty giant crystals from Brazil. You'll also see the Laurent Fluorite, discovered in 2006 in the Mont Blanc massif, and which is the first entirely natural object ever to be classified a "work of art of major heritage interest."
Sensational colours
Minerals are endowed with a wonderful variety of colours — the greens of malachite and dioptase, the blues of topaz and azurite, the reds of ruby and vanadinite, the yellow of mimetite... You will also discover that a single mineral species can adopt several shades, with a series of samples of fluorite in yellow, green, blue, pink, red, black, and perfectly colourless. An animated film explains this chromatic diversity, while another display shows how pigments known since the dawn of time, such as ochre, haematite and lapis lazuli, are extracted from raw minerals.
Fluorescent minerals
The brightness and transparency of a mineral depend on how its structure interacts with light. Depending on their organisation, the atomic lattice may either reflect light waves or allow them to pass. A display shows the phenomena of pleochroism, in which the colour of a crystal changes with the angle of view. The fluorescence of certain minerals is revealed when they are illuminated by ultraviolet rays.