Oberinspector (chief surveyor) of all mining, smelting and salt production in Transylvania. Discovery of tellurium Müller as the Austrian chief surveyor of mines in Transylvania was responsible for the analysis of ore samples. He analyzed gold ore from Kleinschlatten (today Zlatna, Romania). This ore was known as "Faczebajer weißes blättriges Golderz" (white leafy gold ore from Faczebaja) or antimonalischer Goldkies (antimonic gold pyrite), and, according to Anton von Rupprecht, was Spießglaskönig (argent molybdique), containing native antimony. Müller concluded that the ore did not contain antimony, but that it was bismuth sulfide. The following year, he reported that this was erroneous and that the ore contained mostly gold and an unknown metal very similar to antimony. After a thorough investigation which lasted for three years and consisted of more than fifty tests, Müller determined the specific gravity of the mineral and noted the radish-like odor of the white smoke which passed off when the new metal was heated, the red color which the metal imparts to sulfuric acid, and the black precipitate which this solution gives when diluted with water. Nevertheless, he was not able to identify this metal and gave it the names and , as it did not show the properties predicted for the expected antimony. In 1798, the German chemist Martin Heinrich Klaproth isolated the new element from a sample sent by Müller. After a thorough examination of the material he concluded that a new metal was present in the sample. He called it tellurium, but gave the credit of the discovery to Müller. Later life In 1788 he was once more promoted and as Gubernialrath he held a powerful position in the administration of Transylvania. Müller was knighted by Leopold II to the lowest title of nobility, Edler, in the same year. From that point on he carried the name Franz-Joseph Müller Edler von Reichenstein. He was elected as a member of the Berlin Society of Friends of Natural Science. In 1798 Müller became court counsellor and was appointed to the court in Vienna, where he was part of the imperial council. In 1818 Müller retired from his duties but held his position in the council until his death. He became Knight of the Order of Saint Stephen of Hungary in 1818 and became a noble by receiving the title of a Freiherr in 1820. Both honours were granted by the Emperor Franz I (II). Müller died