Ardoise brun-rouge

The brown-red slate Kremer pigment consists of radiolarite from the upper Lechtal, an alpine valley in Austria. This hard, fine-grained sedimentary rock is mainly composed of the microscopic skeletal remains of radiolarians that form an unusually hard, slate-like sediment. Radiolite “grew” very slowly in the Tethys Ocean, so its thick layers actually point to a creation time period of many millions of years. The brown-red color of radiolite is a result of the containing iron and manganese, though its colors range from almost whitish to dark red, green, and brown hues. Because of the extraordinary hardness of radiolite, the stone-age man used this rock for tools and weapons, manufacturing axes, blades, and drills from it. This is way radiolite is also called the “iron of the Paleolithic”.