Rene-Just Hauy

René-Just Haüy was a French priest and mineralogist, who is considered as the founder of modern crystallography. He was born in a poor family in Saint-Just-en-Chaussée, France, on February 28, 1743. He received a scholarship to study at the College of Navarre in Paris, where he later became a professor. He was ordained as a Roman Catholic priest in 1770 and became an honorary canon of Notre Dame in 1785. Haüy's interest in mineralogy was sparked by an accident, when he broke a piece of calcite and noticed that it cleaved along smooth planes that met at constant angles. He repeated the experiment with other minerals and discovered that they had characteristic shapes and angles that could be related to their internal structure. He developed a theory of crystal structure based on the concept of integrant molecules, which were small solid units that stacked together to form crystals. He also formulated the law of rational indices, which stated that the ratios of the intercepts of any crystal face with the axes of a reference system are either integers or simple fractions. He applied his theory to the classification of minerals and described their physical and chemical properties. Haüy published his findings in his four-volume Traité de Minéralogie (1801), which was a landmark work in the history of science. He also wrote Traité de Physique (1803) at the request of Napoleon Bonaparte, and Traité de Cristallographie (1822), which was his last work. He was also known for his studies of pyroelectricity and piezoelectricity in crystals. Haüy was a member of several scientific societies, including the Royal Society of London, the Royal Swedish Academy of Sciences, the French Academy of Sciences, and the Saint Petersburg Academy of Sciences. He received many honors and awards for his contributions to mineralogy and crystallography. He died in Paris on June 1, 1822, at the age of 79. He was buried at the Père Lachaise Cemetery, along with his brother Valentin Haüy, who was the founder of the first school for the blind in Paris.