Due to his innovative work on crystal structure and his four-volume Traité de Minéralogie (1801), he is often referred to as the "Father of Modern Crystallography".

[2][3] Haüy's interest in the services and music of the local church brought him to the attention of the prior of a nearby abbey of Premonstrants.

[2] Through his friendship with his spiritual director, Abbé Lhomond, Haüy became interested first in botany, and after hearing a lecture by Louis-Jean-Marie Daubenton, in mineralogy.

It presented itself in the case of a crystal that the citizen Defrance was kind enough to give me just after it had broken off from a group this enlightened amateur was showing me, and which formed part of his mineralogical collection.

They could observe a crystal's habit and cleavage planes and measure interfacial angles[5][7] with an instrument called a goniometer.

[8] The internal structure underlying the crystal's integrant molecule would not be determinable until the development of X-Ray diffraction technology many years later, in 1902.

[4]: 85 Haüy first stated his law of decrement in Essai d'une théorie sur la structure des crystaux (1784).

One such set was acquired by Martin van Marum, curator of the Teylers Museum and a director of the Hollandsche Maatschappij der Wetenschappen.

[2] During the French Revolution, Haüy refused to take an oath accepting the Civil Constitution of the Clergy, and became a non-juring priest.

[4]: 85 [5][15][16] On August 8, 1793, in spite of the efforts of Antoine Lavoisier, the Académie royale des sciences de Paris was dissolved by the National Convention.

[18][19] Before its suppression, the Academy of Sciences had formed a working group to develop a uniform system of weights and measures for use throughout France.

Lavoisier was a major proponent, and on March 30, 1791, he submitted a plan on behalf of the Commission on Weights and Measures, which was adopted by the Constituent Assembly.

As of January 4, 1793, they determined the weight of a cubic decimeter of distilled water at the temperature of melting ice, the kilogram.

[20] On August 1, 1793, the National Convention passed a decree, in favor of developing uniform weights and measures across France.

On September 11, 1793, they established a Temporary Commission of Weights and Measures made up of twelve scientists, including Haüy, whose task was to carry out the decree.

In October 1794, René Just Haüy was appointed the first curator of the Cabinet of Mineralogy, later known as the Musée de Minéralogie.

[24] Napoleon encouraged Haüy to write Traité élémentaire de physique (1803), and is reported to have read it during his incarceration on Elba in 1814.