Siliceous earth resembles diatomites in physical features and, therefore, finds similar use in the industries. It is used as carrier for catalysts in chemical processes and for mineral fertilizers and herbicides, pesticides and fungicides in agriculture as well as raw material for refination and filtration and constituent of synthetic moulding mass. Siliceous earth differs from diatomites in the mode of origin as it is the product of decalcification of opoka sedimentary rocks and mainly built of opal, a mineraloid gel.
Deposits of siliceous earth occur mainly in tectonic troughs at the margin of the Holy Cross Mts (Piotrowice and Dąbrówka deposits) and in the Lublin Upland (Lechówka), in the form of sedimentary covers overlain by Oligocene rocks.
The Lechówka II deposit is the only siliceous earth deposit currently exploited in Poland but the production is discontinuous and very low, changing from a few tones in 2002 to none in 2008. Exploitation of the remaining deposits has been phased out in the last decades due to unsatisfactory quality of the obtained raw material, mainly usable for making insulation powder.
Table 1 shows resources and the current state of exploration and development of siliceous earth deposits in Poland.
Anticipated economic resources amounted to 2,223 thousand tonnes in 2011 (almost 50 % in A+B+C1 categories). Domestic demand for siliceous earth is fully covered by import.
Prepared by: Robert Bońda