Bacteria encrusted on mineral surface, top view image.

The mineral hornblende is a common metamorphic mineral, and is considered a chemical "garbage can" for many elements of the periodic table. Thus, hornblende is interesting to study in relation to the more general discipline of biological interaction with mineral surfaces because it can supply many different chemical nutrients for bacteria population growth. Bacteria were grown onto the hornblende surface and then killed but not removed. The bacterial deposits that remain are seen as shallow ridges and granular structures on an otherwise planar minerals surface, which shows cleavage planes and crystal steps. This work was done in contact mode and is very easy.