Wooden models of twin crystals

P. Groth & F. Krantz collection (1880)
5 rotatable wooden models of twin crystals (ca. 5.5 to 7.5 cm) from the P. Groth & F. Krantz collection (1880)
From left to right:
top row: gypsum (564), lazulite (589)
center: trydymite (711)
bottom row: titanite (702), calcite (307)
for more info on this collection see Krantz catalog 5, 2nd ed.

private collection