Liesegang Rings – Amazing Geology at Kilimanjaro

Liesegang rings or bands are defined as certain periodically occurring structures in chemical reactions. For example, when silver nitrate solution is dropped onto a gel containing chromate, red, concentric ring-shaped precipitation zones of poorly soluble silver chromate form at certain distances from the spot where it is dropped. This phenomenon was described by Raphael Liesegang (1869-1947) in 1896 and later named after him.

Liesegang rings/bands also occur in porous and clastic rocks (sandstone). Here, Liesegang rings appear long after the sediment has become rock (i.e., it has been compacted and cemented). Stratification and stratification within the Sandton are typically cut by the Liesegang Bands. The clearly visible structures are formed as part of weathering through the diffusion of solutions into the rock with re-precipitation in deeper areas. Brown discoloration usually indicates iron-containing compounds in the penetrated water. The structures form concentrically inwards, roughly parallel to the rock surface, but increasingly follow predetermined fissures and fissures. Liesegang rings can form from the chemical separation of iron oxides and other minerals during weathering. They are zonal rings of minerals or organic matter that form around a core and migrate (diffuse) into the stone.

The so-called "landscape stones" are known as decorative objects or noble wall coverings, the patterns of which are created according to this principle.

Picture 1

Although Liesegang rings are commonly found in sedimentary rocks, rings of iron oxide can also occur in permeable igneous and metamorphic rocks that have been chemically weathered.
Sandstone is a rock that is very widespread on the surface of the earth, occurs on all continents and has been handed down from almost all eras of the earth's history. It is formed by the cementation of loose sand and the addition of coarser or finer sediment particles (clay, silt, boulders).
Sandstone varies in color just like sand does. Sandstone is classified according to the underlying sand. Common and widespread sandstone colors are gray (without admixtures), yellow (due to limonite), brown, red (due to hematite) or white. Sandstone made of pure quartz sand is light gray to white, depending on the color of the quartz grains. The different coloring of sandstones is mostly caused by mineral, sometimes also organic admixtures. Ferrous minerals in particular cause coloring. Silicate minerals containing bivalent iron give the sandstone a greenish hue.

To log this Eartcache, go to the given coordinates and answer the following questions via email or the message center to me

1. What color are the rings and what do you conclude for a mineral origin?

2. Look at picture 1 in the Listing and have a closer look to the marked fields 1,2 and 3.
   a) What different pattern do these bands form in the marked fields? Square, circle, rectangle, triangle, ....?
   b) Are the patterns regular or irregular, differ the diameter and thickness of these rings/bands?

3. Do Liesegang rings form in sediments before or after they are lithified (turned to stone)?

4. Some ring-like patterns in nature (e.g. tree rings) are caused by seasonal variations in temperature or rainfall. What do you think, seasonal variations have an impact on the Liesegang ring patterns in sedimentary rocks? Briefly explain your answer.

5. Take a photo of yourself and/or a personal item (e.g. your GPS) and attach it to your log!