# Crystal model made of cardboard

### Model 722

### Description

This crystal model is rhombohedral of class C_{3}^{v}.

In the collection are 45 crystal models made of cardboard by the company Dr. F. Krantz, Bonn. (Notation of Schoenfliess is used).

### Additions

System | Class | Model | | | System | Class | Model |

Triclin | C_{1} |
861 | | | Rhombic | C_{2}^{v} |
739 |

C^{i}=S_{2} |
854 | | | V | 734, 752 | ||

Monoclin | C^{s}=C_{1}^{h} |
855 | | | V^{h} |
729, 742, 754 | |

C_{2} |
727, 728, 743 | | | ||||

C_{2}^{h} |
741, 753 | | | ||||

Rhombohedral | C_{3} |
756 | | | Tetragonal | C_{4} |
853 |

(trigonal) | C_{3}^{i} |
740 | | | C_{4}^{h} |
747 | |

C_{3}^{v} |
722 | | | C_{4}^{v} |
744, 757 | ||

D_{3} |
724, 733 | | | D_{4} |
730 | ||

D_{3}^{d} |
723, 736, 738 | | | D_{4}^{h} |
748 | ||

Trigonal | C_{3}^{h} |
856 | | | S_{4} |
859 | |

D_{3}^{h} |
857 | | | V^{d} |
721 | ||

Hexagonal | C_{6} |
missing | | | Cubic | T | 726, 745 |

C_{6}^{h} |
735 | | | T^{h} |
725 | ||

C_{6}^{v} |
746 | | | T^{d} |
750, 751 | ||

D_{6} |
755 | | | O | 731, 732 | ||

D_{6}^{h} |
749 | | | O^{h} |
737, 758 |

Showcase of this model is Case number U 21

### References

*Separataband M4 im Mathematischen Institut*, Katalog Dr. F. Krantz, Bonn p. 425.

Ewald. *Handb. d. Physik*, Bd. XXIV, p. 204.

Niggli. *Geometrische Kristallographie*, p. 132,133. Online version

Schoenflies, Arthur(1923). *Theorie der Kristallstruktur*.