Recent Studies

Is the calcite in the form of plaster or chalk? (From Tel es Safi, Israel)

The study of atomic disorder in minerals found in archaeological sites, offers many exciting and important opportunities to gain insights into archaeological processes. There are several reasons for this:

1. The atomic disorder signature of a particular mineral, often reflects the manner in which it was formed. Thus the same mineral formed in different ways can be differentiated. We have applied this concept to differentiating between calcite produced under geogenic conditions, as ash during the burning of the calcium oxalate component of wood, and as plaster formed by heating geogenic calcite at around 800 C in order to produce calcium oxide. For more details see (Regev et al., 2010). Figure 2 shows examples of a grinding curve for different calcite controls. For a theoretical analysis of this effect, see Poduska et al (Poduska et al., 2010).

Figure 2. The basis for assessing the extent of atomic defects in the crystal lattice is the comparison of peak widths in the infrared spectrum. Peak widths are however also influenced by the extent of grinding of the sample (a). So in order to separate between the two effects, a sample is ground repeatedly to produce a grinding curve (b). The locations of the grinding curves in this plot of normalized peak heights reflects the different extents of defects in the crystal lattice. Figure is from (Regev et al., 2010).