*3.1. Chemical Data*

Chemical composition of krasnoshteinite is given in Table 1. The empirical formula calculated on the basis of O + Cl = 33 atoms per formula unit is H32.47Al7.87Si0.01B2.03Cl3.79O29.71 or, after recalculation of the anionic part and taking into account crystal-structure data, (Al7.87Si0.01)Σ7.88[B2.03O4(OH)2][(OH)15.74(H2O)0.26]Σ16[(Cl3.79(OH)0.21]<sup>Σ</sup>4·7H2O. The ideal formula is Al8[B2O4(OH)2](OH)16Cl4·7H2O, which requires Al 24.65, B 2.47, Cl 16.19, H 3.69, O 53.00, total 100 wt.%, or, in oxides, Al2O3 46.58, B2O3 7.95, H2O 32.93, Cl 16.19, –O=Cl –3.65, total 100 wt.%.

**Table 1.** Chemical composition (in wt.%) of krasnoshteinite in elements and in oxides (Al, Si, Cl, and O: average data for 7 spot electron-microprobe analyses).


Krasnoshteinite is insoluble in water and slowly dissolves in cold diluted HCl without effervescence. The obtained solution shows characteristic color reaction, with quinalizarin clearly indicating boron presence.
