Which three factors are used to classify clastic sedimentary rocks?

Which three factors are used to classify clastic sedimentary rocks?

• A. Grain size, sorting, and shape
• B. Color, mineral composition, and porosity
• C. Texture, density, and hardness
• D. Luster, streak, and cleavage

Answer: (A)

Grain size, sorting, and grain shape are the factors that determine how clastic sedimentary rocks are classified. The size of the grains sets the basic category (like sandstone, siltstone, or shale) because particle scale tells you about the energy of the environment where the sediment was deposited. Sorting describes how uniform the grain sizes are across the rock: well-sorted rocks have grains similar in size, which points to a more uniform energy conditions during deposition, while poorly sorted rocks contain a mix of sizes and indicate more variable or short-lived conditions. Grain shape, from rounded to angular, reveals how far the grains traveled and how much abrasion they endured; more rounded grains reflect longer transport or reworking, while angular grains suggest shorter transport or rapid deposition. Other properties like color, mineral composition, or porosity are important for understanding the rock’s appearance or storage potential, but they don’t define the basic way these rocks are classified. Texture and other mineral properties may be informative, but the trio of grain size, sorting, and shape best captures the depositional history that distinguishes clastic rocks.

Grain size, sorting, and grain shape are the factors that determine how clastic sedimentary rocks are classified. The size of the grains sets the basic category (like sandstone, siltstone, or shale) because particle scale tells you about the energy of the environment where the sediment was deposited. Sorting describes how uniform the grain sizes are across the rock: well-sorted rocks have grains similar in size, which points to a more uniform energy conditions during deposition, while poorly sorted rocks contain a mix of sizes and indicate more variable or short-lived conditions. Grain shape, from rounded to angular, reveals how far the grains traveled and how much abrasion they endured; more rounded grains reflect longer transport or reworking, while angular grains suggest shorter transport or rapid deposition.

Other properties like color, mineral composition, or porosity are important for understanding the rock’s appearance or storage potential, but they don’t define the basic way these rocks are classified. Texture and other mineral properties may be informative, but the trio of grain size, sorting, and shape best captures the depositional history that distinguishes clastic rocks.