Karl Ludwig Felix Machatschki (22 September 1895 – 17 February 1970) was an Austrian mineralogist.
He studied at the University of Graz, obtaining his habilitation in 1925; in 1927 he joined the group of Victor Goldschmidt in Oslo for one year.
[1] In 1928 he published Zur Frage der Struktur und Konstitution der Feldspäte, a paper in which he develops the concept of the atomic structure of silicates and formulates the construction principle of feldspars.
[2] In 1946 he published Grundlagen der allgemeinen Mineralogie und Kristallchemie ("Fundamentals of general mineralogy and crystal chemistry").
[3] The "Felix-Machatschki-Preis" is an award given by the Österreichische Mineralogische Gesellschaft in recognition of outstanding international scientific work in the field of mineralogy.