Zhemchuzhnikovite is an oxalate mineral of organic origin; formula NaMg(FeAl)C<sub>2</sub>O<sub>4</sub>÷8H<sub>2</sub>O. It forms smoky green crystals with a vitreous lustre and is found in Russian coal mines. It is named after Yury Zhemchuzhnikov (1885âÂÂ1957), a Russian clay mineralogist.