Building stones — which has the lowest crushing strength? Among the following commonly known stones, which one typically exhibits the least crushing (compressive) strength and is therefore the weakest for structural use?

Introduction / Context:
Selection of stone for construction depends heavily on compressive strength, durability, and weathering resistance. Understanding the relative strengths of common stones helps in choosing suitable applications and avoiding failures.

Given Data / Assumptions:

• Typical ranges of compressive strength for unweathered rock types.
• Laboratory-tested values at standard moisture content.
• Comparative, not absolute, assessment.

Concept / Approach:

Granite, slate, and many sandstones are strong to very strong rocks. Marble (metamorphosed limestone) generally has moderate to high compressive strength. Chalk is a soft, porous limestone with very low compressive strength, unsuitable for load-bearing masonry without special treatment.

Step-by-Step Solution:

Verification / Alternative check:

Rock mechanics tables report chalk strengths often an order of magnitude lower than compact limestones or granites, confirming chalk as the least strong in crushing.

Why Other Options Are Wrong:

• Granite and slate are commonly used for heavy loads.
• Marble, while not as strong as granite, exceeds chalk.
• Many sandstones exceed chalk strength substantially.

Common Pitfalls:

• Confusing decorative value (marble) with structural strength.
• Assuming all limestones are similar; chalk is a weak variety.

Final Answer:

Chalk.