Grain Size Analysis Using Optical Method
Grain size analysis is the examination and measurement of the size and shape of individual grains that make up a sediment or sedimentary rock. It is an important tool in geology to help study the transportation, deposition, sorting and age of the material. Traditional grain size analysis is conventionally done by sieving, which has several drawbacks such as being time and labor consuming, only providing limited information about the sample, and not being able to measure submillimeter grain sizes. Optical methods of grain size analysis, such as the laser diffraction and dynamic image analysis, are becoming a popular alternative due to their ability to measure grain sizes and shape quickly, accurately and non-destructively (Jeffery and Steele, 2006).
Laser diffraction is a method used to measure grain size distribution by examining the diffraction of a laser beam, which passes through the sample, on a diffractometer screen. This method works by sweeping a laser beam through a sample of sediment or other material, which will diffract in certain directions depending on the size and spacing of the material’s particles. A diffraction pattern is generated on the screen and this pattern is then analyzed using a computer program to determine the grain size distribution. The advantage of this method is that it is relatively fast and efficient compared to sieving and it can be used to measure particles as small as 0.1 μm (Videira, et al., 2018).
Dynamic image analysis is a method that uses digital images of the sample to measure its grain size and shape. The sample is placed on a glass plate and a digital camera is used to take a series of photographs. These photographs are then analyzed using a computer program to measure the size and shape of the sample’s particles along with other parameters such as their orientation. This method is relatively fast and can measure particles as small as 1 μm (Videira, et al., 2018).
The advantages of optical methods of grain size analysis are that they are generally non-destructive and provide quick and accurate measurements of particle size and shape which are essential for sedimentary or paleoenvironmental studies. Additionally, they are relatively easy to use and do not require significant amounts of manpower or time to obtain results.
In conclusion, optical methods such as laser diffraction and dynamic image analysis are becoming increasingly popular for grain size analysis due to their ability to provide quick and accurate measurements without the time and labor used in traditional methods. In the future, these methods could become the new standard for grain size analysis due to their enhanced speed, efficiency and accuracy.
