Question

According to the USDA classification, the size of fine sand fraction is:

• A. 0.5 mm
• B. 0.25 mm
• C. 0.1 mm
• D. 0.05 mm

Hint:

USDA Sand Fraction Boundaries:
- Medium/Fine sand boundary = \(0.25\text{ mm}\)
- Fine/Very fine sand boundary = \(0.10\text{ mm}\)
- Very fine sand/Silt boundary = \(0.05\text{ mm}\) (which is also the boundary between sand and silt).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Soil texture is determined by the relative proportions of sand, silt, and clay particles.
To classify these soil separates, standard classification systems, such as the United States Department of Agriculture (USDA) system, define specific particle size diameter limits for each fraction.

Step 2: Detailed Explanation:
Let us review the complete USDA particle size classification for sand fractions:
- Very coarse sand: \(2.0\text{ mm to }1.0\text{ mm}\) in diameter
- Coarse sand: \(1.0\text{ mm to }0.5\text{ mm}\) in diameter
- Medium sand: \(0.5\text{ mm to }0.25\text{ mm}\) in diameter
- Fine sand: \(0.25\text{ mm to }0.10\text{ mm}\) in diameter
- Very fine sand: \(0.10\text{ mm to }0.05\text{ mm}\) in diameter
- Silt: \(0.05\text{ mm to }0.002\text{ mm}\) in diameter
- Clay: Less than \(0.002\text{ mm}\) in diameter
The fine sand fraction spans the size range from \(0.25\text{ mm}\) down to \(0.10\text{ mm}\).
Therefore, the lower limit that defines the fine sand fraction is \(0.10\text{ mm}\), which is represented by Option (C).

Step 2: Final Answer:
According to the USDA classification, the size limit of the fine sand fraction is 0.1 mm.