The probable potential minerals in organic plant tissues according to the XRD database were: arcanite
([K.sub.2]S[O.sub.4]), calcium borate hydrate ([Ca.sub.3] [(B[O.sub.3]).sub.2]*[H.sub.2]O), calcium silicide (Ca[Si.sub.2]), cristobalite (Si[O.sub.2]), celestine (SrS[O.sub.4]), calcium phosphate (CaHP[O.sub.4]), hydrogrossular ([Ca.sub.3][Al.sub.2][(Si[O.sub.4]).sub.3-x][(OH).sub.4x]), manganite (MnO(OH)), potassium nitrate (KN[O.sub.3]), potassium oxalate hydrate ([K.sub.2][C.sub.2][O.sub.4].
As another example, the mineral arcanite ([K.sub.2]S[O.sub.4]) is typically present in small amounts, usually less than 1 % by mass, in portland cement clinker.
The presence of syngenite, as seen in XRD patterns, suggests possible pre-hydration or cement storage issues as it generally represents a reaction between arcanite (or other alkali sulfates) and gypsum.
The salicylic acid and methanol (SAM) extraction dissolves alite ([C.sub.3][S.sup.1]), belite ([C.sub.2]S), and free lime (CaO), leaving behind a residue of the tricalcium aluminate ([C.sub.3]A) and ferrite ([C.sub.4]AF) interstitial phases as well as minor phases including periclase (MgO) and alkali sulfates such as arcanite (K[bar.S]), thenardite (N[S.sub.S]), and langbeinite (K[M.sub.2] [[bar.S].sub.3]), calcium sulfates (gypsum, bassanite, and anhydrite), and carbonates (calcite and dolomite).
1 = alite 2 = belite 3 = aluminate 4 = ferrite 5 = periclase 6 = arcanite 7 = aphthitalite 8 = void Record the index designations for later use as some phases will be absent from some materials.
For example, arcanite (K[bar.S]) contains only potassium and sulfur, so if the potassium X-ray map is assigned to the green channel and the sulfur X-ray map is assigned to the yellow channel, pixels belonging to arcanite will be white (see Fig.
4 and K4 are particularly interesting, as a lot of the initial compounds are still present, for example arcanite
[K.sub.2]S[O.sub.4], marcasite Fe[S.sub.2], and potassium calcium sulphate [K.sub.2][Ca.sub.2]([S[O.sub.4]).sub.3].