Pear wood model (Quartz hyalin rhombifère) and front page of Traité de Minéralogie (Paris 1801) by R. J. Haüy
Cardboard and glass models by Dr. F. Krantz
A crystal model is a teaching aid used for understanding concepts in crystallography and the morphology of crystals. Models are ideal to learn recognizing symmetry elements in crystals.
^Cristallographie ou description des formes propres a tous les corps du regne mineral, dl II, 1783