(1743–1822) French mineralogist
Haüy, whose father was a poor clothworker, was born in St. Just in France. His interest in church music attracted the attention of the prior of the abbey, who soon recognized Haüy's intelligence and arranged for him to receive a sound education. While in Paris, his interest in mineralogy was awakened by the lectures of Louis Daubenton. He became professor of mineralogy at the Natural History Museum in Paris in 1802. His Traité de mineralogie (Treatise on Mineralogy) was published in five volumes in 1801 and Traité de cristallographie (Treatise on Crystallography) in three volumes in 1822.
Haüy is regarded as the founder of the science of crystallography through his discovery of the geometrical law of crystallization. In 1781 he accidentally dropped some calcite crystals onto the floor, one of which broke, and found, to his surprise, that the broken pieces were rhombohedral in form. Deliberately breaking other and diverse forms of calcite, he found that it always revealed the same form whatever its source. He concluded that all the molecules of calcite have the same form and it is only how they are joined together that produces different gross structures. Following on from this he suggested that other minerals should show different basic forms. He thought that there were, in fact, six different primitive forms from which all crystals could be derived by being linked in different ways. Using his theory he was able to predict in many cases the correct angles of the crystal face. The work aroused much controversy and was attacked by Eilhard Mitscherlich in 1819 when he discovered isomorphism in which two substances of different composition can have the same crystalline form. Haüy rejected Mitscherlich's arguments.
Haüy also conducted work in pyroelectricity. The mineral haüyne was named for him.