Glass crystal model

 

F. Krantz (ca. 1900)
Glass model of a monoclinic crystal (ca. 20 cm) from a series.
A small glued label indicates: "I | Dr. F. Krantz | Bonn a. Rh."

Internal silk threads materialize the crystallographic axes and illustrate with the corresponding colours the dispersion of the optic axes and of the acute bisectrix for blue, yellow and red light.

private collection

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the glass model as seen along the crystallographic b-axis
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the glass model as seen perpendicular to the b-axis

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top view of the model

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detail of the label
 
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