ADVENTURES IN AN IRON BIRDBATH: NANOSTRUCTURE OF IRON OXIDES AND A NANNOBACTERIAL CONNECTION
Fallen leaves lie in the birdbath water and become coated with fluffy, pumpkin-orange iron oxide, Munsell 5YR 5-7/6-8. This forms clumps (? colonies) and sheets of 30-100 nm balls. When the leaf is placed in 10% HCL for one week, the iron oxide is removed but the balls remain insoluble, thus we conclude that they are acid-resistant cells of nannobacteria that precipitated the iron oxide.
At the iron/water contact on the bottom of the pool, brittle crusts of iron oxide form, about the color of a dark chocolate bar, 1OR 2/2. This is strongly magnetic and shows a wide variety of morphologies. Most common are euhedral hexagonal plates 1 ìm thick by 2-12 ìm wide; but these are made of stacked sheets about 30 nm wide that are studded with 30 nm balls and ovoids. In other crystals the balls range 50-150 nm. The plates have the morphology of hematite, but the strong magnetism suggests delta-FeOOH. Also there are fields of 3 ìm rosettes; 30-70 nm balls join into straight chains, then into sheets, finally into flowers resembling carnations.
The balls that make up the crystals and carnations are interpreted as nannobacterial cells, much the same size and shape as those that form other minerals, harden human arteries, and are found in Martian meteorites. In the iron birdbath the iron oxides are (nanno)bacteriogenic.