Question

The diameter of fine particle in sand fraction according to USDA is:

• A. 0.25-0.10 mm
• B. 0.50-0.25 mm
• C. 0.05-0.002 mm
• D. 2.00-1.00 mm

Hint:

Rank the USDA sand subclasses by size from coarse to fine.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The United States Department of Agriculture (USDA) system splits the broad texture class sand into five finer size classes, based only on particle diameter.

Step 2: Key Formula or Approach:
The five USDA sand subclasses, from largest to smallest particle size, are very coarse sand (2.00-1.00 mm), coarse sand (1.00-0.50 mm), medium sand (0.50-0.25 mm), fine sand (0.25-0.10 mm) and very fine sand (0.10-0.05 mm). Anything from 0.05 mm down to 0.002 mm is classed as silt, and anything below 0.002 mm is clay.

Step 3: Detailed Explanation:
The question asks for the diameter range of the fine sand subclass. Matching this against the standard USDA scale above, fine sand covers particles from 0.25 mm down to 0.10 mm.
The range 0.50-0.25 mm actually belongs to medium sand, not fine sand.
The range 0.05-0.002 mm is far too small for any sand subclass, this is the range used for silt.
The range 2.00-1.00 mm is the coarsest class, very coarse sand, the opposite end of the scale from fine sand.

Step 4: Final Answer:
Fine sand has a diameter of 0.25 mm to 0.10 mm, so option 1 is correct.