Of all the experimental sciences used to determine the arrangement of atoms in crystalline solids, crystallography is by far the best. Modern crystallographers use a process called x-ray crystallography to study the structure of crystalline molecules, but the pioneers of this science had no such fancy technology. Instead they did it the old fashioned way, which for them was actually the new fashioned way because they were literally making it up as they went.
Kepler Creates Crystallography (Kinda)
One of the first notable hypotheses on crystallography comes from the famous German mathematician and astronomer Johannes “Big Bad John” Kepler. In his 1611 writing, A New Year’s Gift of Hexagonal Snow (roughly translated from the German), Kepler hypothesized that the hexagonal symmetry of snowflakes was due to the regular packing of spherical water particles.
More than half a century later, in 1669, Danish scientist Nicolas “Big Nick” Steno conducted the first experimental investigations of crystal symmetry. Steno found that the angles between the faces of a particular type of crystal are the same across all examples of said crystal.
Haüy No Haüy
More than a full century later, in 1784, the French mineralogist and “Father of Modern Crystallography” René Just “Big René” Haüy discovered that simple stacking patterns of blocks of the same shape and size can be used to describe every face of a given crystal. Haüy’s work led to the further discovery that crystals are constructed on a regular, repeating three-dimensional array of atoms/molecules, in which a single unit cell repeats indefinitely along three principal, and not necessarily perpendicular, directions.
Building off these discoveries, in 1839 Welsh mineralogist William Hallowes “Big Willie” Miller devised a way to give each face of a crystal a unique label of three small integers. These integers are now known as “the Miller Indices,” which to this day are used to identify and classify crystals.
Combining Haüy’s discoveries and Miller’s work, a group of late-19th century scientists (German mineralogist Johann “Big Johann” Hessel, French crystallographer Auguste “Big Augie” Bravais, Russian mineralogist Evgraf “Big Ev” Fedorov, German mathematician Arthur “Big Art” Schoenflies, and English geologist William “Big Bill” Barlow) compiled a complete catalog of all possible crystal symmetries.