Nearly pure alunogen
occurs in veins in sulphur at Sanni.
It is observed that the black cotton soil predominant with montmorillonite, quartz and microcline revealed new peaks pertaining to alunogen
and bassanite due to contamination with sulfuric acid.
Neither was confirmed the presence of alunogen
[A[l.sub.2](S[O.sub.4])3-16[H.sub.2]O] or alunite [KAL,(S[O.sub.4])2[(OH).sub.6] ], which seem to be much more common in the NW part of the BCB (Lentschig-Sommer, 1960, 1961; Williams and Robinson, 1998; Prikryl et al., 2007).
They are somewhat shaggy-looking, as they are spotted by gray, white and greenish shards and subhedral crystals of other soluble sulfates such as alunogen
and halotrichite ...
Solubility diagrams were constructed using the equations for amorphous aluminium hydroxide, alunite, and AlOHS[O.sub.4] plus equations and p[K.sup.0] values from the literature for alunogen
(Nordstrom 1982) and basaluminite (Adams and Rawajfih 1977).
Bigham and Nordstrom (2000) concluded that hydrobasaluminite and basaluminite (formed by the dehydration of hydrobasaluminite) should precipitate at higher pH than zaherite, and with decreasing pH the sequence should continue with aluminite, then the more crystalline jurbanite and alunogen
[[Al.sub.2][(S[O.sub.4]).sub.3].17[H.sub.2]O] at even lower pH.
[Al.sub.2](S[O.sub.4])[.sub.3] * 17[H.sub.2]O (SO)
Other minor associated minerals include kalinite, mirabilite, alunogen
, pickeringite and melanterite.