Idealized models of crystals were a great aid in the study of natural crystals as another type of crystallographic projection besides drawing.
Crystal models were constructed out of plaster and wood Since early as the seventeenth century. It is possible that the Danish geologist Nicolaus Steno may have created models of quartz crystals to verify his revolutionary concept that the interfacial having the same angle. However, the earliest citation of using models in connection with mineralogy occurs in Linneaus’ writings where the Swedish naturalist prepared crystal models of wood perhaps as early as 1735. But it was not until the 1780s that crystal models became a tool widely used in crystallographic studies.
In 1772, Rom´e de L’Isle published the first edition of his famous Essai de Cristallographie. The book emphasized physical characteristics to define crystallography and mineralogy as a science.
The plates illustrated in the essay included, as he called “deveopments.” They were unfolded surfaces of the crystals that look like line drawings but reconstructable to a three-dimensional crytstal shape.
His first publication was a big success so he planned for a much extended second edition of the book including 483 illustrations of crystals and minerals from his private collection. Rom’e asked the engraver Swebach Desfontaines and his two students Arnould Carangeot, and Claude Lemina to create terra cotta models of the crystals to be sent as a premium for his subscribers.
After a prototype of a contact goniometer had been invented by Carangeot, it became possible to measure interplanar angles close to about half of a degree because of using terra cotta models instead of natural crystals.
About twenty years later, wood appeared to be a more convenient material than clay (terra cotta) to produce crystal models. Especially, pear wood made it possible to get smooth faces and sharp edges and to have the high accuracy of dihedral angles which are required for the production of the three-dimensional objects. Also, René Just Haüy tried the two-dimensional drawings using wooden crystal models in the atlas volume of his “Traité de Minéralogie” (1801). For example, some models illustrating crystal twins and Haüy’s figures have been evaluated to have higher angular accuracy.
Since their introduction by Romé de l’Isle and Haüy, the increasing amount of crystal models were produced, and, at the same time, the models were demanded by the purposes of teaching and mineral collection. In l880, a company, “Krantz,” founded by Adam August Krantz in 1833, proposed a series of 743 pear wood models compiled for teaching ideas by the crystallographer Paul Groth and seven years later a supplementary collection of 213 models yielded. Those outcomes resulted from co-working with renowned scientists and collectors. Also, Friedrich Krantz produced a collection of 928 models including most of the Groth models.
With the technically advanced quality of models in their production, mineralogists and crystallographers enabled designing their series of models, thereby applying various materials, such as plaster, cast iron, lead, brass, glass, porcelain, cardboard, as well as pear wood. Krantz offered different sized wooden models including 5, 10, 15–25 cm. In addition to the several wooden models, various forms and materials of the models were available — a massive cut and different colored polished glass, cardboard models, wire crystal models, crystal lattice models, models with rotating parts, etc. In particular, glass models were specified by the crystallographic axes with colored silk threads or the holohedral form of cardboard inside.
References
- Schuh, Curtis (2007) Mineralogy & Crystallography: On the history of these sciences from beginnings through 1919. Tucson, Arizona
- https://www.krantz-online.de/en/about_us/history.html
- http://www.mineralogy.eu/index.html
