Grain Size Chart

Grain Size Chart in MM

The Size Chart is a must have for field geologists to describe samples. This pocket size chart is not only handy and cheap it’s also cost effective for the professional in the field.

The chart has recessed die-cut sample cavities filled with precision sieved sedimentary particles, each representing a specific category called grain size. These particles are permanently mounted to the chart so they will not wear out. These particles are examples of clastic sediments, which are broken down through mechanical processes like abrasion. The samples are classified according to the Wentworth scale so geologists can classify and describe grain sizes in an organized and standardized way. The chart includes categories such as very coarse sand, which is essential for initial site evaluations and soil descriptions. Grain classification and analysis of sedimentary rocks is key to understanding the processes of erosion, transport and deposition that formed them.

With the Grain Chart geologists can quickly and easily refer to the grain classification for their samples. The compact size of the chartfits in a pocketbackpack or field bag so it’s always with you when you need it. Its portability makes it perfect for fieldwork and on site analysis so you don’t need bulky reference materials or equipment.

The precision sieved sedimentary particles on the chart were selected to represent a range of granular material sizes commonly found in geologic samples. So geologists can classify and describe grain sizes with precision.

The Size Chart is a proven and trusted tool used by field geologists worldwide, classified according to the Wentworth scale. Its simple and rugged design makes it a long lasting investment that can withstand the demands of field work. Whether in the lab or in the field this grain chart is an essential tool for geologists.

Don’t settle for anything less than accurate size classifications. Choose the Grain Chart and be consistent and reliable every time.

Grain size is a fundamental concept in sedimentary geology, meaning the average diameter of clasts (particles) of clastic sediments and rocks. Grain size is key to classifying sediments and rocks, understanding their origin and depositional environment and predicting their physical properties. In this article we will explore the world of grain size, classification, measurement and applications.

Grain Size Classification

Size classification is a critical step in sedimentary geology where we can categorize sediments and rocks into different classes based on their grain size. The classification system helps in distinguishing between different types of particles, such as sand grains, silt, and clay, which is crucial for understanding sedimentary processes. The most widely used classification system is the Udden-Wentworth scale which divides sediments into four actual grain samples and major classes: ruditic (> 2 mm), arenitic (0.0625 – 2 mm), siltitic (0.004 – 0.0625 mm) and lutitic (< 0.004 mm). These classes are further sub divided into more specific categories like coarse sand, medium sand and fine sand. The Wentworth scale provides a framework to understand the processes that formed sediments and rocks, the agent of erosion/transport and the velocity of the current that transported the sediment.

Grain Size Measurement and Applications

Sieve Analysis and Other Measurement Methods

Grain size can be measured by several methods including sieve analysis, contouring/counting on thin sections and visual comparison with grain charts. Sieve analysis is the most common method where a sediment sample is passed through a series of sieves with decreasing mesh sizes to separate particles of different sizes. The resulting grain size distribution can be plotted as a size frequency distribution to get information about the texture and composition of the sediment. Phi units (Φ) are also used to describe sediment size in hydrogeology, with the conversion to real world units given by the formula: Diameter (mm) = 1/2^n where n = phi (Φ) value.

Practical Uses of Grain Size

Grain size has many practical uses in sedimentary geology:

• Understanding the origin and depositional environment of sediments and rocks

• Predicting the physical properties of sediments and rocks, strength, density and porosity

• Classifying sediments and rocks into different classes for classification purposes

• Interpreting the geological history of an area, tectonic and climatic conditions* Identify grain size and potential economic deposits, oil and gas reservoirs and mineral deposits

In summary grain size is a fundamental concept in sedimentary geology and its classification, measurement and applications are key to understanding the origin, composition and properties of sediments and rocks. By using grain charts, sieve analysis and phi units geologists can get valuable information about the geological history of an area and make informed decisions about resource exploration and management.

Grain Size

Grain size is a fundamental concept in geology, referring to the diameter of individual grains of sediment or lithified particles in clastic rocks. It is a critical property used to describe sediment and is essential in understanding the geomorphic setting of a site. Grain size determines how far a piece of sediment can travel before coming to a halt, and it plays a crucial role in the formation of different types of rocks. By analyzing grain size, geologists can infer the energy and environment of deposition, which helps in reconstructing past geological conditions and processes.

Grain Size Classification and Applications

Grain size classification is a vital tool in geology, engineering, and environmental science. The Wentworth scale, created by J. W. Wentworth in 1885, is a widely used classification system that defines size ranges for classes of sediment. This scale includes categories such as boulder, cobble, very coarse gravel, coarse gravel, medium gravel, fine gravel, very fine gravel, granule, very coarse sand, coarse sand, medium sand, fine sand, very fine sand, silt, mud, clay, and colloid. Each of these categories has specific size ranges that help geologists and engineers classify and describe sediments accurately.The Krumbein phi scale is a logarithmic scale that modifies the Wentworth scale, providing a more precise way to measure grain size. It is computed using the equation φ = -log2(D/D0), where φ represents the Krumbein phi scale, D is the diameter of the particle, and D0 is a reference diameter equal to 1 mm. This equation allows for a consistent and standardized measurement of grain size, which is crucial for comparing sediment samples from different locations.

Grain size classification has many applications in geology, engineering and environmental science. It is used to classify sediment and rocks, understand the geomorphic setting of a site and determine how far a sediment can travel before coming to a halt. The Wentworth scale and Krumbein phi scale are used in these fields to classify sediment and rocks based on their size and shape to interpret geological history and assess potential economic deposits.

Grain Size

The Wentworth scale defines the following size ranges:

• Boulder: > 256 mm, > 10.1 in

• Cobble: -6 to -8, 64–256 mm, 2.5–10.1 in

• Very coarse gravel: -5 to -6, 32–64 mm, 1.26–2.5 in

• Coarse gravel: -4 to -5, 16–32 mm, 0.63–1.26 in

• Medium gravel: -3 to -4, 8–16 mm, 0.31–0.63 in

• Fine gravel: -2 to -3, 4–8 mm, 0.157–0.31 in

• Very fine gravel: -1 to -2, 2–4 mm, 0.079–0.157 in

• Granule: 0 to -1, 1–2 mm, 0.039–0.079 in

• Very coarse sand: 1 to 0, 0.5–1 mm, 0.020–0.039 in

• Coarse sand: 2 to 1, 0.25–0.5 mm, 0.010–0.020 in

• Medium sand: 3 to 2, 125–250 µm, 0.0049–0.010 in

• Fine sand: 4 to 3, 62.5–125 µm, 0.0025–0.0049 in

• Very fine sand: 8 to 4, 3.9–62.5 µm, 0.00015–0.0025 in

• Silt: > 8, < 3.9 µm, < 0.00015 in

• Mud: > 10, < 1 µm, < 0.000039 in

• Colloid: > 10, < 1 µm, < 0.000039 in

These are the limits for each class, to classify and describe sediments. By using the Wentworth scale and Krumbein phi scale geologists can measure grain size and understand the processes that formed the sediments. This is key to interpreting geological history, assessing potential economic deposits and making informed decisions on resource exploration and management.