Flint

Layers

Very abundant, the flint is like silicon accident in the Craie or the Calcaire in the form of nodules, and in grounds Argile ux, some of these grounds (as in High-Normandy or Champagne) being deteriorations of chalk.

Formation

The flint is formed when the sea water is saturated with Silice. This phenomenon occurs either in tropical Climat, when the ground S reds underwent a physical and chemical deterioration (Météorisation) intense, or by the decomposition of the Exosquelette S silicieux of marine organizations such as the sponge S. silica precipitates then on the bed of the oceans by filling the cavities left in the Craie (or another form of Calcaire) and crystallizes in nodules. The nodule, while being formed, épigenise surrounding limestones, i.e. the molecules of Carbonate of calcium are replaced with one by silica molecules, without changing the original structure of the rock; thus the flint grows at the expense of limestone. The phenomenon of formation of a flint nodule stops when the limestone deposits bury it and deprive it of the silica contribution dissolved in water. The envelope of the nodule, the cortex, is composed of impurities (organic deposits,…) pushed back towards outside at the time of the growth of flint. One can find fossils in a flint nodule, in general rather badly preserved.

Use

The flint was used throughout the Préhistoire and of the Protohistoire for the manufacture of Outil S and Arme S, because of its faculty to split according to constant and controllable laws, by forming sharp edges (break conchoïdale).

It was also employed within the framework of the Techniques of production of fire: struck against a rock rich in iron or a piece of steel, the flints spark likely to be fixed by materials such as the Amadou.

XVIIe at the XIXe century, the flint was used as a striker for rifles (Platine with flint).

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