text: * 1801 - René Just Haüy published his multi-volume Traité de Minéralogie in Paris. A second edition under the title Traité de Cristallographie was published in 1822.
  * 1801 - Déodat de Dolomieu published his Sur la philosophie minéralogique et sur lespèce minéralogique' in Paris.
  * 1815 - René Just Haüy published his Law of Symmetry.
  * 1815 - Christian Samuel Weiss, founder of the dynamist school of crystallography, developed a geometric treatment of crystals in which crystallographic axes are the basis for classification of crystals rather than Haüy’s polyhedral molecules.
  * 1819 - Eilhard Mitscherlich discovered crystallographic isomorphism.
  * 1822 - Friedrich Mohs attempted to bring the molecular approach of Haüy and the geometric approach of Weiss into agreement.
  * 1823 - Franz Ernst Neumann invented a system of crystal face notation, by using the reciprocals of the intercepts with crystal axes, which becomes the standard for the next 60 years.
  * 1824 - Ludwig August Seeber conceived of the concept of using an array of discrete (molecular) points to represent a crystal.
  * 1826 - Moritz Ludwig Frankenheim deriveed the 32 crystal classes by using the crystallographic restriction, consistent with Haüy’s laws, that only 2, 3, 4 and 6-fold rotational axes are permitted.
  * 1830 - Johann F. C. Hessel publishes an independent geometrical derivation of the 32 point groups (crystal classes).
  * 1832 - Friedrich Wöhler and Justus von Liebig discovered polymorphism in molecular crystals, using the example of benzamide.
  * 1839 - William Hallowes Miller invented zonal relations by projecting the faces of a crystal upon the surface of a circumscribed sphere. Miller indices are defined which form a notation system in crystallography for planes in crystal (Bravais) lattices.
  * 1840 - Gabriel Delafosse, independently of Seeber, represented crystal structure as an array of discrete points generated by defined translations.
  * 1842 - Moritz Frankenheim derived 15 different theoretical networks of points in space not dependent on molecular shape.
  * 1848 - Louis Pasteur discovered that sodium ammonium tartrate can crystallize in left- and right-handed forms and showed that the two forms can rotate polarized light in opposite directions. This was the first demonstration of molecular chirality, and also the first explanation of isomerism.
  * 1850 - Auguste Bravais derived the 14 space lattices.
  * 1869 - Axel Gadolin, independently of Hessel, derived the 32 crystal classes using stereographic projection.
  * 1877 - Paul Heinrich von Groth founded the journal Zeitschrift für Krystallographie und Mineralogie, and served as its editor for 44 years.
  * 1877 - Ernest-François Mallard, building on the work of Auguste Bravais, published a memoir on optically “anomalous” crystals (that is, those crystals the morphology of which seems to be of greater symmetry than their optics), in which the importance of crystal twinning and "pseudosymmetry" were used as explanatory concepts.
  * 1879 - Leonhard Sohncke listed the 65 crystallographic point systems using rotations and reflections in addition to translations.
  * 1880 - Pierre Curie and Paul-Jacques Curie discovered piezoelectricity in crystals. In 1881 they demonstrated the reverse effect: that crystals could be made to deform when subject to an electric field.
  * 1888 - Friedrich Reinitzer discovered the existence of liquid crystals during investigations of cholesteryl benzoate.
  * 1889 - Otto Lehmann, after receiving a letter from Friedrich Reinitzer, used polarizing light to explain the phenomenon of liquid crystals.
  * 1891 - Derivation of the 230 space groups (by adding mirror-image symmetry to Sohncke’s work) by a collaborative effort of Evgraf Fedorov and Arthur Schoenflies.
  * 1894 - William Barlow, using a sphere packing approach, independently derived the 230 space groups.
  * 1894 - Pierre Curie described the now called Curie's principle for the symmetry properties of crystals. 
  * 1895 - Wilhelm Conrad Röntgen on 8 November 1895 produced and detected electromagnetic radiation in a wavelength range now known as X-rays or Röntgen rays, an achievement that earned him the first Nobel Prize in Physics in 1901. X-rays became the major mode of crystallographic research in the 20th century.