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ROME' DE L’ISLE, Jean-Baptiste Louis. (Born: Gray, France, 29 August 1736; Died: Paris, France, 7March 1790) .

Romè de I’Isle received little formal scientific education, 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 the mineralogist and chemist B. Sage, who directed his interest to mineralogy. Rom´e de I’Isle supported himself through the patronage of several wealthy friends whose collections of minerals, coins, and gems he supervised and catalogued. Although his scientific work became well known outside of France, he never succeeded in breaking into the French scientific establishment. A proposal for his election to membership in the Academie des Sciences failed and
he lived to see his own achievements in mineralogy and crystallography overshadowed by the work of R.J. Hauy.
The Cristallographie ranks as one of the great contributions to the science of crystals. In it Rom´e de l’Isle attempted to make a comprehensive classification of crystals. By the time he wrote this volume, he was extremely familiar with the subject, and this work greatly supassed all previous works in scope and detail. To apply his classification, he adopted a morphological approach in which he attempted to relate the diverse forms of crystals of the same substance. As a general morphological concept he introduced the idea of the “primitive form.” All crystals of the same inorganic substance, no matter how different in appearance had a fundemental and common geometrical form—the primative form—to which their actual crystal shapes related. The justification for this idea was derived from the previous work of Carl Linneaus who had tried to expain the genesis of minerals by means of an analogy with the procreation of living creatures, and classified cystals by the similarities of their crystallized forms.Rom´e de l’Isle identifies 110 crystal forms by which minerals rystallize. Grouped under each of these shapes are described the minerals that exhibit similar habit, including the approximate angles between crystal faces.
These forms were all derived form a common saline ingredient in every mineral that worked at a molecular level. Although he believes that these primitive forms existed, it is never made clear how they should be defined for any group of crystals. Rom´e was able to greatly expand upon this idea in the second edition.
By the time of its publication, Rom´e had made crucial advances towards a quantitative crystallography. This had been made possible by the recent invention of the contact goniometer by his student, Arnould Carangeot. This simple device used for measuring crystalline angular dimensions, led him to generally enunciate for the first time, the fundemental quantitative law of crystallography—the law of constant interfacial angles.
Previously, Henckel, Bartholin and Steno had observed this constant in pyrite, calcite and quartz, respectively; however, Rom´e was the first to state it as a general trueism 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. To this purpose, the 2nd edition increases to over 450 the number of possible crystal forms, and providing for each accurate angle measurements between different crystal surfaces made with the goniometer. Armed with his law, he was able to somewhat elaborate on his definition of the primitive form and how it related to the external crystal, but Rom´e never made the theoretical leap that allowed Hauy to spin an elegant theory from essentially the same information. None the less, Rom´e 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. Very scarce. In this collection catalog, the famous French crystallographer fully describes about 750 metallic minerals from his own cabinet. Included are specimens consisting of pure metals as well as natural alloys and combinations with sulfur. Basic division is based upon the principle metals and semimetals contained in the described specimens and include gold, silver, copper, iron, tin, lead, mercury, antimony, zinc, bismuth, cobalt, arsenic and sulfur.
Under each of these headings, the specimens are divided based upon their form and chemical composition. For each item described, notes on the origin, associated minerals, locality, size and the estimated weight of contained precious metals is presented. The catalog is well referenced, and if a particular specimen was given to Rom´e, the supplier’s name is included in the description.
During his lifetime, Rom´e accumulated a large collection of minerals and crystals. Following his death in 1790, it was purchased by Francois Gillet de Laumont [1747-1834], French Inspector General of Mines and one of the greatest mineral collectors of his time. In 1835, De Laumont’s collection was purchased by the French goverment, where today its remains are preserved in Paris at the Sorbonne.