(Wydawnictwa AGH, 2012) Grochowina, Anna; Gołębiowska, Bożena; Pieczka, Adam
Sareopside (Fe,Mn,Mg)$_{3}$(PO$_{4}$)$_{2}$ and graftonite (Fe,Mn,Ca)$_{3}$(PO$_{4}$)$_{2}$ are the dominant minerals found in the phosphate nodules from the Michałkowa pegmatite in the Sowie Mountains block.
In fracture veins found in the so-called diabases of Niedźwiedzia Góra near Cracow the authors have identified ferriferrous varieties of sepiolite: $Ca_{0.09}(Mg_{2.35}Fe^{3+} _{0.82}Fe^{2+} _{0.33}Mn_{0.05})_{\Sigma 3.55}[(Si_{5.92}Al_{0.07}Fe^{3+} _{0.02})O_{15}](OH)_{2} \cdot 6H_{2}O$ and saponite: $(Ca_{0.018}K_{<0.01})(Mg_{1.55}Fe^{3+} _{0.61}Fe^{2+} _{0.38}Al_{0.16}Ti_{0.01})_{\Sigma 2.71}[(Si_{3.46}Al_{0.37}Fe^{3+} _{0.17})O_{10}] (OH)_{2} \cdot 4H_{2}0$, two minerals rarely occurring in the nature. They are accompanied mainly by quartz (sometimes with chalcedony) and calcite, whereas less frequently by pyrite, marcasite, sphalerite, barite, fluorapatite and Ti-Fe oxides (ilmenite?). The veins represent a distinct system that must be interpreted as a result of epithermal postmagmatic activity. The sepiolite rich in iron, the minerals of the $SiO_2$ group, calcite, barite and Fe and Zn sulphides crystallized directly from solutions in rock fractures. The iron-rich saponite is, in turn, a product of alteration of the diabase rubble present initially in the fractures (apatite and Ti-Fe oxides are its relicts), affected by these solutions. The saponite must have originated as a ferrous variety in a reducing environment. Its current, ferriferrous character is an effect of later changes imparted by descending, oxygen-rich waters, percolating through the fractures after the erosion removed overlaying Carboniferous rocks and an upper part of the diabase sill.
