Texture

Texture The physical appearance or character ( ) of a rock Describing Textures: texture of sedimentary rocks is described as "clastic", meaning that they are composed of discrete particles that are compacted and cemented together. An example of a non-clastic texture would be crystalline material. The textures of sedimentary rocks are also important to take note of and to describe. Features such as grain shape, roundness and sorting of grains can tell you a lot about the environment in which the rock was formed. The degree of roundness in the grains as well as the degree of sorting can reflect the amount of weathering and transport that the sediment went through. Long transport tends to result in well-rounded and well-sorted grains, whereas short transport results in poorly sorted angular grains.

Describing textures in sedimentary rocks includes not only the grain shape (i.e. roundness) and sorting, but also features like porosity and intergrain relationships. Pore space between grains makes a good reservoir for oil, gas, etc.

Intergrain relationships allow us to divide sedimentary textures into two main categories: 1. 2.

crystalline textures (Non-clastic ) : with interlocking grains. clastic textures: with rounded to angular grains that are stuck together.

Textural Maturity is also related to the degree of roundness and sorting of the grains. As sediment is transported, the more easily weathered rock

fragments are broken down, leaving those grains which are most stable and resist weathering. Quartz is a good example of this. The composition of a rock can tell us a lot about the conditions in which it was formed!

Grain Size Analysis:Method of studying soils, sediments, sands, or rock by determining the size, distribution, and proportion of selected particles. Grain size is the most fundamental physical property of sediment. - Geologists and Sedimentologists use information on sediment grain size to study trends in surface processes related to the dynamic conditions of transportation and deposition.

- Engineers use grain size to study sample permeability and stability under load. - Geochemists use grain size to study kinetic reactions and the affinities of fine-grained particles and contaminants. - Hydrologists use it when studying the movement of subsurface fluids .

The objectives of a grain-size analysis are to accurately measure individual particle sizes or hydraulic equivalents, to determine their frequency distribution, and to calculate a statistical description that adequately characterizes the sample.

Heavy Minerals:-

The large variety of often distinctive heavy minerals found in sediments can provide valuable information for interpreting stratigraphy and determining the provenance of a sediment. When minerals of economic importance such as gold, or kimberlite indicator minerals such as pyrope, are observed in the heavy mineral fraction, they can often be traced to a source in bedrock. Furthermore, the heavy mineral fraction can provide information on the nature of geochemical anomalies that would be otherwise difficult to obtain.