John Walter Gruner (12 July 1890, Neurode, now Nowa Ruda – 1981) was a German-born American mineralogist, crystallographer, and geologist.
[2] After completing secondary school education, he worked for two years in a wholesale house and saved enough money to emigrate in 1912 from Germany to the U.S.A.
For the academic year 1917–1918 at the University of Iowa, he studied geology under George Frederick Kay (1873–1943) and took courses in physical and analytical chemistry.
[4] In 1926 he went to study X-ray analysis in mineralogy for a year at the University of Leipzig under Friedrich Rinne and Ernst Schiebold [de].
[4][7] Gruner became known as mineralogy's leading expert on Minnesota's iron formations and Colorado's radioactive mineral deposits.
The focus of much of his scientific work was the determination of the crystallographic structures of phyllosilicates, such as dickite, vermiculite and glauconite, which he examined with an X-ray diffractometer he developed himself.