Sandstone is one of the most common types of sedimentary rock and is found in sedimentary basins throughout the world. It is often mined for use as a construction material or as a raw material used in manufacturing. When used in construction it tends to have very few lines or marks in it and is all of one colour. It is a very strong, hard material and will weather very slowly. It can be yellow, red, grey and many other colours.
Varying thicknesses of rock deposits are possible. The thickness of each layer of rock depends upon the flow of water and the way in which it has been deposited. If the same type of material is washed down with steady water flow the depth of the sedimentary rock can be quite constant creating smooth rock with strong bonds. This type of rock is suitable for building because both the bedding planes and vertical strengths are good.
If the water flow is variable into the sea or lake, different amounts and types of material can be washed down creating thin layers of sediment with weak layers of rock. Thin layers of rock generally have weak vertical strength too meaning that it is unlikely that this rock would be suitable for building.
Liesegang rings also called Liesegangen ringsor Liesegang bandsare colored bands of cement observed in sedimentary rocks that typically cut-across bedding. These exhibit bands of minerals that are arranged in a regular repeating pattern. Liesegang rings are distinguishable from other sedimentary structures by their concentric or ring-likeappearance. 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. Though Liesegang rings are considered a frequent occurrence in sedimentary rocks, rings composed of iron oxide can also occur in permeable rocks that have been chemically weathered
In order to log a find against this EarthCache you will need to answer some questions and send answers to me through my Geocaching profile or through the Messenger Facility.
1) please describe the sandstone at GZ making reference to its grain size and coherency
2) what is shown at the published coordinates ? A band or a full ring?
3) at stage 2 what is shown in the walls? A band or a full ring?
4) what mineral is responsible for the colour of the banding ?