Due to weathering over time, the cooling of the volcanic rock produced beautiful earth minerals and patterns in various undulating mounds in seven distinct colours. The place has become one of Mauritius’ main tourist attractions since the 1960s. Nowadays, the dunes are protected by a wooden fence and visitors are not allowed to climb on them, although they can look at the scenery from observation outposts placed along the fence. Curio shops in the area sell small test-tubes filled up with the coloured earths.
The main feature of the place is that since these differently coloured sands spontaneously settle in different layers, dunes acquire a surrealistic, striped colouring. This phenomenon can also be observed, on a smaller scale, if one takes a handful of sands of different colours and mixes them together, as they’ll eventually separate into a layered spectrum.
The sands have formed from the decomposition of volcanic rock (basalt) gullies into clay, further transformed into ferralitic soil by total hydrolysis; the two main elements of the resulting soil, iron and aluminium, are responsible for red/anthracite and blue/purplish colours respectively. The different shades of colour are believed to be a consequence of the molten volcanic rock cooling down at different external temperatures (hence rates), but the causes of their consistent spontaneous separation are yet to be fully clarified.