Crystal-originated pits

J R. Glauber was probably the first to form artificial niter beds. By throwing putrefiable matter of both vegetable and animal origin into pits and adding wood ashes, he obtained in due time a saltpeter eaith from which he extracted a solution which, on evaporation, yielded crystals of this salt. Glauber believed that the function of die putrid material was merely to draw the niter from the air (41). 

However, some flakes show the presence of pits growing in the flake whilst others are in the process of disintegrating completely, presumably due to imperfections in the original flake crystal structure, as shown in Figure 25 A and B respectively. It may be noted that the pits are highly erratic and have no clear structure. 

The visual examination and analysis of the various minerals by SEM-EDS has revealed etch pits on the mineral surfaces of pyrite crystals at DH-4/80m, (Fig. 6) DH-3/—527 m. In contrast, the pyrite keeps its original form in the rock samples from DH-4/130m (Fig. 6) and DH-3/—344 m. The etch pits have also been observed on silicate mineral surfaces in certain fractures and fractured zones (Fig. 6). Most of the silicate mineral surfaces are considered to be coated by stable clay minerals in the fractured zones. The predominant clay mineral of the fracture fillings in the moderately and... 

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