JEAN BAPTISTE ROMÉ DE L'ISLE (1736 - 1790). Cristallographie. Paris: Chez Didot jeune [etc.], 1783.

JEAN BAPTISTE ROMÉ DE L'ISLE (1736 - 1790). Cristallographie. Paris: Chez Didot jeune [etc.], 1783.

Romé de l'Isle received little formal scientific education during his youth in France - his interest in natural history developed during his military service and travel in India and the Orient. In 1764 after his return to France, he was befriended by a mineralogist and chemist who directed his interest to mineralogy, which became his life's interest.

This book is actually a revised and considerably expanded version of Romé de l'Isle's 1772 text Essai de Cristallographie. As a general morphological concept, he proposed that all crystals of the same inorganic substance, no matter how different in appearance, had a fundamental and common geometrical form - the primitive form - to which their actual crystal shapes related.

In all, Romé de l'Isle identified 450 crystal forms by which minerals crystallize. Under each of these shapes he described the minerals that exhibit similar habit, including the approximate angles between crystal faces. It was while making this classification that he was led to his discovery of the fundamental law of quantitative crystallography: the law of constant interfacial angles.

Others, including Niels Stensen, had previously observed this constancy in individual minerals such as pyrite, calcite, and quartz; however, Romé de l'Isle was the first to state it as a general truism of the physical world. It meant that regardless of the dissimilar appearance of crystals, specimens of the same species would always show identical angle measurements between common crystal faces. In addition, this discovery provided mineralogy with the first exact measurement that could be published without interpretation, and thus be disseminated to other researchers.

Armed with his law, Romé de l'Isle was able to speculate on how the primitive form related to the external crystal, but he never made the theoretical leap that allowed René Just Haüy to spin an elegant theory from essentially the same information. Nonetheless, Roméde l'Isle captured information from his crystallographical laws and, together with his broadened concept of the relationship between crystal form and chemical composition, he made the Cristallographie into the finest mineralogical treatise written to the time.

Curtis P. Schuh, Mineralogy & Crystallography: An Annotated Bibliography of Books Published 1469 through 1919. Tucson: privately published, 2005, p1256-1257.

List of books in exhibit (links go to author information and references)