Figure 6
Calcite crystal in scalahedron form and a wooden model produced by Haüy to illustrate his `stacked bricks' theory on the shape of crystals. According to legend, René Just Haüy had this inspiration when he dropped and broke a calcite crystal (Iceland spar). He noticed that all the fragments were identical in form and were, without exception, parallelepipeds; these were totally different from the irregular shards obtained from broken glass. Source: Voyage dans le cristal; adapted from (i) calcite cristal (copyright Muséum de Grenoble), (ii) wooden model (copyright Collection des Minéraux de Jussieu, UPMC, Paris), (iii) painting of Haüy (copyright Musée de Minéralogie, Mines ParisTech, Paris). |