Anselme Boece de Boot (?, 1634) published " Historia gemmarum and lapidum " (1609).
Towards 1650, Gassendi took as a hypothesis that crystals derive from polyhedrons.
Towards 1660, Hooke carried out microscopic crystals observations and studied their outer shape.
In 1669 Nicolas Stenon (1638 - 1687) observed the constancy of the dihedral angles between faces of certain crystals. He published " Solido will intra solidum naturaliter contento ".
Erasmus Bartholin (1625 - 1698) studied the double refraction of Iceland spar; this is the birth of crystalline optics.
Huyghens C (1629 - 1695) gave an explanation of the double refraction of Iceland spar within the framework of his wave theory of light.
Towards 1670, Boyle observed that in certain crystals, cleavage is often parallel with the lamellas structure.