Similar to the above sample, we dissolved it first in hydrochloric acid and then in hydrofluoric acid. The minor components obtained from the insoluble fraction are manganese oxides and unidentified organic matter. The sample is a gray-brown sediment that contains a black layer. This black layer contains, as its major components, calcite, clay and quartz. Following the procedure of acid dissolutions as described above, the minor components found are unidentified organic matter and possible humic substances.
Plans call for additional activity area samples to be analyzed.
But for the time being it seems unlikely that any of the analyzed samples represent residues from burning. Rather, the two analyzed dark facade stains seem due to natural deposition of manganese oxides, while the one drain sample seems to be composed of sediments containing minerals and small amounts of humic and other organic materials, all of which would be consistent with the drain's apparent function as a water conduit.