Sands with heavy minerals
The main source of heavy minerals e.g. in the Baltic Sea are secondary clastic deposits in a form of sandy sediments of the shallow-water and beach area. The Baltic heavy minerals concentrations occur within the banks: Odrzana and Słupska. Sands with heavy minerals were documented north of the Bay of Pomerania, within the Polish Exclusive Economic Zone of the Baltic Sea – in the north-eastern part of the Ławica Odrzana (the Odrzana bank). The documentation was the result of the longstanding and multistage geological studies, concentrated on the exploration of the Bay of Pomerania geological structure, on the searching of useful minerals and possibilities of their usage. Sands of the Ławica Odrzana deposit are well sorted an usually contain above 90% of quartz. The main components of heavy minerals are translucent minerals in the amount of 51.6% to 75.9%, with the less significant participation of non-translucent minerals – in the amount of 24.1% to 48.4%.
The contribution of heavy minerals in sands varies. Within the layer between the surface and the depth of 0.5 m the contribution is between 1.4% and 21.7% (the mean 4.4-4.5%), whereas within the sand deposit layer between 0.5 m and 1.0 m below the sea bottom it is between 2% and 4.2% (the mean 2.5-3.3%). The limit value is the 2% isoline of the heavy minerals contribution in the sands. The main useful components in Ławica Odrzana deposit are heavy minerals such as: ilmenite (FeTiO3), rutile (TiO2), zircon (ZrSiO4) and garnets (Fe, Ca, Mg, Mn)3(Al, Fe, Cr)2(SiO4)3. The percentage contribution of particular minerals in the total amount of heavy minerals in the deposit is as follows: ilmenite – 31%; zircon – 5%; leucoxene – 4%; rutile – 4%; garnets – 32%.
It is possible to enlarge the resources of sands with heavy mineral in an area located north of the documented Ławica Odrzana deposit, however it requires a detailed exploration of the prospective areas located in this region. In the zircon concentrate from the Ławica Odrzana sands, the rare earth elements (REE) content is as follows: Ce – 3.9 g/kg, La – 1.9, Nd – 1.7, Pd, Y, Gd, Sa within the range of 0.5-0.2 g/kg; whereas in the zircon concentrate from the Ławica Słupska sands the following contents were indicated: Ce – 2.3 g/kg; La – 1.1 g/kg; Nd – 0.96 g/kg, Pd, Y, Gd, Sa within the range of 0.1-0.3 g/kg. In the prospective fields of the Łąwica Słupska deposit, the average content of heavy minerals is from 3.1 to 13.1 weighted percentage (maximum of 45 weighted percentage) and is similar to this from the Ławica Odrzana deposit. The total heavy minerals resources have not been estimated, but according to the preliminary assessments in 1 tonne of sand the following amounts of minerals occur: about 17.40 kg of ilmenite, 2.5-3.5 kg of zirconium, rutile and monazite, and 9.5-30.0 kg of garnet*.
The useful components from the Ławica Odrzana deposit could be used for the colorants and coat production, for the production of high resistance steel, artificial materials, paper, electronics, in the biomedical engineering, in the ceramic and glass industries, in nuclear power and for the production of abrasives and fibers. Quartz sands remaining after a heavy minerals separation might be used in the glass industry, for the production of moulding sands and in the building industry.
Prepared by: Wojciech Miśkiewicz
* Kramarska R., Szamałek K., 2020 – "Minerały ciężkie". In: "Bilans perspektywicznych zasobów kopalin Polski wg stanu na 31.12.2018 r." (eds. Szamałek K., Szuflicki M., Mizerski W.): 418. PIG-PIB, Warszawa [in Polish].