Liesegang rings

The process by which Liesegang rings develop is not completely understood.

The chemical garden experiment was successful but the Liesegang rings failed to operate correctly due to a friction in parts of the mechanism.

Liesegang rings may form from the chemical segregation of iron oxides and other minerals during weathering.

Liesegang rings are distinguishable from other sedimentary structures by their concentric or ring-like appearance.

Liesegang rings, cone-in-cone structures, raindrop impressions, and vegetation-induced sedimentary structures would also be considered secondary structures.

Liesegang rings are a phenomenon seen in many, if not most, chemical systems undergoing a precipitation reaction, under certain conditions of concentration and in the absence of convection.

Liesegang rings (also called Liesegangen rings or Liesegang bands) are colored bands of cement observed in sedimentary rocks that typically cut-across bedding.

Though Liesegang rings are considered a frequent occurrence in sedimentary rocks, rings composed of iron oxide can also occur in permeable igneous and metamorphic rocks that have been chemically weathered.

Being only weakly indurated by small amounts of iron oxide, sometimes seen as Liesegang rings (banding) at Rock City, it is considerably softer and very much more easily eroded than the calcite concretions.

Liesegang rings are often referred to as great examples of geochemical self-organization, meaning that their distribution in the rock does not seem to be directly related to features that were established prior to Liesegang ring formation.

It was research into photographic emulsions that initially lead to his personal discovery of Liesegang rings (note he himself was not the first person to observe the effect but they bear his name since he devoted so much time to researching them.)

The precise mechanism from which Liesegang rings form is not entirely known and is still under research, however there is a precipitation process that is thought to be the catalyst for Liesegang ring formation referred to as the Ostwald-Liesegang supersaturation-nucleation-depletion cycle.

Liesegang rings can have the appearance of fine lamination and can be mistaken for laminae when parallel or subparallel to the bedding plane, and are more easily differentiated from laminae when the rings are observed cutting-across beds or lamination.

One popular mechanism suggested by geochemists is that Liesegang rings develop when there is a lack of convection (advection) and has to do with the interdiffusion of reacting species such as oxygen and ferrous iron that precipitate in separate discrete bands which become spaced apart in a geometric pattern.