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Wooden model illustrating Haüy's laws of decrement
Krantz catalog number 18
Krantz glass crystal model
biscuit porcelain crystal model

wooden models on display socle
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Early
Crystal Models
Introduction
The first real collections of crystal models were produced by
Romé de l'Isle. He actually offered sets of small (ca
3 cm) models made of "terra cotta" in order to stimulate the
sales of the expensive 4 volume set of his book "Cristallographie"
(1783). The models were manufactured by his co-workers Arnould
Carangeot, Lhermina and Swebach-Desfontaines, who produced numerous
large sets (up to 448 models in each set). In order to exactly
transfer interplanar angles from natural crystals to the terra
cotta models, Carangeot invented and designed a prototype of
a contact goniometer. This instrument, that proved to be an
invaluable tool in geometric crystallography, enabled the measurement
of interplanar angles with a precision of about half a degree.
Almost two decennia later, René Just Haüy introduced
wooden crystal models to illustrate the two-dimensional drawings
in the atlas volume of his "Traité de Minéralogie" (1801). For
the production of crystal models, wood appeared to be much more
convenient than clay. Especially pear wood permitted getting
smooth faces, sharp edges and accurate dihedral angles required
for the production of these three-dimensional objects. In general
the angular accuracy was very high and some models, especially
those illustrating crystal twins and Haüy's figures of decrement,
still appear as masterpieces of fine woodwork and carving. Skilful
craftsmen such as Pleuvin, Beloeuf and Lambotin (to name only
a few) became specialists in this field and the models they
offered were highly esteemed.
After their introduction by Romé de l'Isle and Haüy,
crystal models were increasingly demanded both by scholars for
teaching purposes as well as by mineral collectors. The quality
of the models improved due to the technical progress in their
production. Several mineralogists and crystallographers started
designing their own series of models. Although pear wood kept
a prominent place, models were also manufactured using materials
like plaster, cast iron, lead, brass, glass, porcelain, cardboard,
etc.
In 1833, Adam August Krantz (who studied pharmacy and later
"Geognosie" at the "Bergakademie Freiberg") founded the "Krantz"
company in Bonn. Four years later Krantz moved to Berlin and
sold minerals, fossils, rocks and basically acquired a monopoly
in the production of crystal models made of pear wood or walnut.
Ever since its foundation, the firm was always in contact with
renowned scientists and important collectors. Hence in 1880
Krantz proposed a series of 743 pear wood models compiled for
teaching purposes by the crystallographer Paul Groth. Seven
years later a supplementary collection of 213 models was available.
At the onset of the 20th century, Friedrich Krantz (a nephew
of August Krantz, with a degree in mineralogy) supported by
his teacher the crystallographer Carl Hintze, offered a collection
of 928 models including most of the Groth models. Later, and
along with many other productions, a Dana collection of 282
models was manufactured. Krantz offered a choice of collections
of wooden models in different sizes (5, 10, 15-25 cm). In addition
he sold a variety of glass models having the crystallographic
axes illustrated by colored silk threads or with the holohedral
form made of cardboard inside. Also available were models in
massive cut and polished glass (colored and uncolored), cardboard
models, wire crystal models, crystal lattice models, models
with rotating parts, etc.
Over the years, Krantz published numerous detailed catalogues
of the collections he offered; they constitute a precious documentation.
In 1994, Ulrich Burchard edited detailed drawings (generated
by means of the program "SHAPE") of the models of the Groth
and Krantz main collection with an indication of the original
stamped numbering. Two years later, the same author described
the supplementary series together with an alphabetic listing
of all mineral species in both collections. The two volumes
devoted to this collection constitute an invaluable documentation
for the collector in order to appreciate, to compare and to
identify these fascinating objects.
References
- Burchard, U. (1994, 1996) The P. Groth & F. Krantz
collection of 743 crystal models 1880 and The supplementary
collection of 213 crystal models of P. Groth & F. Krantz
1887 © Ulrich Burchard (Freising, Germany)
- Haüy, R.J. (1801) Traité de Minéralogie. 5 Vols.
Paris
- Krantz F. (1913) Allgemeiner mineralogisch-geologischer
Lehrmittel-Katalog für den Schulgebrauch. Katalog
Nr 18. Zweite Auflage. I. Teil. Bonn [1913 and earlier editions]
- Romé de l'Isle, J-B. L. (1783) Cristallographie, ou
description des formes propres à tous les corps du règne
minéral, dans l'état de combinaison saline, pierreuse ou
métallique. 4 Vols. Paris
- Schuh, Curtis (2007) Mineralogy & Crystallography:
On the history of these sciences from beginnings through
1919. Tucson, Arizona
- Touret, L. (2004) Crystal models: milestone in the
birth of crystallography and mineralogy as sciences
in Dutch Pioneers of the Earth Sciences. Ed. by R.W. Visser
and J. Touret, Koninklijke Nederlandse Akademie van Wetenschappen,
Amsterdam
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