Born in Graz on 4 November 1908 as the son of the zoologist Dr. Adolf and Bertha Meixner. Mineralogy already interested Meixner during his school years. His school leaving examination homework was centered around the theme of "New mineral discoveries in the eastern Austrian Alps I and II". He pursued this theme until his death; originally he published in such works as the Bulletins of the Styrian Natural Science Society and subsequently in the Carinthia II of the Carinthian Natural Science Society.

Meixner completed a high school teaching degree in chemistry and natural history at the University of Graz in 1935. In the autumn of 1936, he obtained his PhD. His dissertation dealt with the mineral lazulite and its types of deposits.

In the autumn of 1938, Meixner became technical assistant of the mineralogical - petrographical department of the Natural History Museum of Vienna. Shortly thereafter, he became curator and in 1940 he was appointed lecturer for mineralogy at the University of Vienna. In the same year, Meixner was called up for military service.

After the war, he started working as assistant surveyor of mines. Later on, he became the mineralogist at the Hüttenberg mine of the Austrian Alpine Coal, Iron and Steel Company.

In 1969, Meixner took over the newly established Institute for Mineralogy, Petrography and Economic Mineralogy at the University of Salzburg. In his more than 400 scientific and popular publications, Meixner devoted himself mainly to mineral-topographical and paragenetic issues. An aqueous Mg-Al-hydroxide from the quarry "In der Gleisen" near Nöchling in the Waldviertel was named ‘meixnerite’ in honour of Meixner by Koritnig and Süsse. Meixner died on 19 December 1981 in Salzburg.