* 1723 - Moritz Anton Cappeller introduced the term ‘crystallography’.
* 1766 - Pierre-Joseph Macquer, in his Dictionnaire de Chymie, promoted mechanisms of crystallization based on the idea that crystals are composed of polyhedral molecules (primitive integrantes).
* 1772 - Jean-Baptiste L. Romé de lIsle developed geometrical ideas on crystal structure in his Essai de Cristallographie'. He also described the twinning phenomenon in crystals.
* 1781 - Abbé René Just Haüy (often termed the "Father of Modern Crystallography") discovered that crystals always cleave along crystallographic planes. Based on this observation, and the fact that the inter-facial angles in each crystal species always have the same value, Haüy concluded that crystals must be periodic and composed of regularly arranged rows of tiny polyhedra (molécules intégrantes). This theory explained why all crystal planes are related by small rational numbers (the law of rational indices).
* 1783 - Jean-Baptiste L. Romé de lIsle in the second edition of his Cristallographie' used the contact goniometer to discover the law of constant interfacial angles: angles are constant and characteristic for crystals of the same chemical substance.
* 1784 - René Just Haüy published his Law of Decrements: a crystal is composed of molecules arranged periodically in three dimensions.
* 1795 - René Just Haüy lectured on his Law of Symmetry: “[…] the manner in which Nature creates crystals is always obeying [...] the law of the greatest possible symmetry, in the sense that oppositely situated but corresponding parts are always equal in number, arrangement, and form of their faces”.