Miloschite

A bluish, massive to earthy variety.


The first mineral explorations in Serbia began in the early 19th century (1835), when Baron Sigmund August Wolfgang Freiherr von Herder, the supreme mining elder of Saxony, arrived at the invitation of Prince Miloš Obrenović. His work led to the discovery of an unknown blue mineral in the municipality of Kraljevo, in the village of Rudnjak, on the western slopes of mountain Željin, Serbia. As a sign of gratitude, he named this mineral “miloschin” after Prince Miloš Obrenović. In the following years, Professor of Mineralogy August Breithaupt analyzed its mineralogical and chemical composition and published the results in a paper titled “Bestimmung neuer Mineralien; Serbian or Miloschin”. In the third revised edition of Dana’s Mineralogy from 1850, “miloschin” is referred to as a chromiferous compact mineral, probably a mechanical mixture. Subsequent investigations of this mineral were conducted by other authors, who reported their findings in the following years. Kersten reported that this new mineral is a hydrated aluminum silicate with chromium, while Kenngott states that it consists of a crystalline part, probably kaolin, and an amorphous part. Somewhat later, in the sixth revised edition of Dana’s Mineralogy, the name was first introduced as “miloschite” to comply with English terminology. In 1916, the first American occurrence of “miloschite” was reported, where it was recognized as a separate mineral species of chromium kaolinite. They felt that their mineral from Nevada closely resembled the published descriptions of “miloschite”. However, they were not in possession of an original sample of “miloschite” from the type locality—Rudnjak, and they considered it desirable to compare the two minerals. New insight into this mineral emerged in 1942, when Grim and Rowland reported the first differential thermal analysis, suggesting that it was chromium-bearing kaolinite and/or halloysite. Later, in 1953, Maksimović defined it as a chromium-bearing halloysite, citing the higher H2O content in its structure. Maksimović [15], based on thermogravimetric analysis (TGA) and X-ray diffraction (XRD) results, and Stangačilović, based on differential thermal analysis (DTA) results on the original samples of “miloschite”, unequivocally confirmed that the sample is chromo-bearing halloysite. Maksimović, in his article from 1972, mentions that “miloschite” was also found in other localities in Serbia, as well as that “miloschite” occurs in various shades of blue and that the intensity of the color of the mineral increases with the increase in chromium content. Brookins published a paper in 1973 where he raised a question regarding the term “miloschite” and stated that it was originally intended to refer to a chromiferous kaolinite and/or halloysite, since no X-ray diffraction data were known anywhere in the world. Nevertheless, he decided to declare the samples from The Geysers (Sonoma County, CA, USA) as “miloschite”, to publish their XRD data, and to claim that this was the first unambiguous identification of “miloschite” as chromium-bearing kaolinite. Maksimović and Brindley mention and distinguish the occurrence of chromium-bearing halloysite alongside chromium-bearing kaolinite and tosudite near Takovo (Serbia), while Maksimović and co-authors mention chromium-bearing dickite and chromium-bearing kaolinite from Teslić, Yugoslavia (now Bosnia and Herzegovina). Lastly, in the Clay Minerals Society Glossary of Clay Science from 2020, it was stated that “miloschite” represents an obsolete term for chromium-bearing kaolinite, which probably originates from Brookins’ claims.