Haüys

Haüys is a term that can refer to several things, primarily related to crystallography and mineralogy, named after the French mineralogist René Just Haüy. Most commonly, it refers to the concept of the "molécule intégrante" or integral molecule, a fundamental idea proposed by Haüy. This concept suggested that crystals are composed of tiny, identical, and indivisible building blocks arranged in a regular, repeating pattern. These integral molecules were thought to be the smallest units that retained the chemical properties of the substance and were responsible for the crystal's characteristic external shape. This theory, although later refined and replaced by the atomic and molecular structures we understand today, was revolutionary in its time and provided a framework for understanding crystal growth and form.

In some contexts, "Haüys" might also informally refer to crystallographic measurements or diagrams that illustrate the structure or cleavage planes of a mineral, in homage to Haüy's pioneering work in describing and classifying crystals. It is important to distinguish between the theoretical concept and any broader, less precise applications of the term. The legacy of Haüy lies in his systematic approach to studying crystals and his groundbreaking, albeit ultimately superseded, theory of their internal structure.