Rock and mineral hardness (Mohs scale) – identify the softest among the following Which of the following is the softest material in the list commonly referenced in building geology?

Difficulty: Easy

Correct Answer: Talc

Explanation:


Introduction / Context:
Hardness, often expressed using the Mohs scale (1 to 10), compares the ability of a material to resist scratching. In construction and geology, knowing relative hardness helps anticipate wear, polishability, and the suitability of stones for flooring, cladding, and tooling. This question asks you to pick the softest option among common building-related materials.


Given Data / Assumptions:

  • Options: marble (metamorphic rock), diamond (mineral), talc (mineral), quartz (mineral).
  • We refer to standard Mohs hardness values.
  • The task is to identify the softest one.


Concept / Approach:

Talc defines the bottom of the Mohs scale at hardness 1. It is extremely soft and can be scratched by a fingernail. Quartz is much harder, at 7. Marble, being composed mainly of calcite, sits near 3 on Mohs scale; diamond, the hardest known natural material, defines hardness 10. Therefore, the softest choice is talc.


Step-by-Step Solution:

1) Recall Mohs reference points: talc = 1, diamond = 10, quartz = 7, calcite = 3.2) Marble ≈ calcite composition → hardness ≈ 3.3) Compare all: talc (1) < marble (~3) < quartz (7) < diamond (10).4) Conclude talc is the softest among the given options.


Verification / Alternative check:

Scratch tests and standard mineralogy charts consistently place talc at the bottom of the scale, confirming the selection.


Why Other Options Are Wrong:

Marble: Harder than talc; usually about 3 due to calcite content.

Diamond: Hardest known natural mineral at 10; certainly not softest.

Quartz: Significantly harder at 7; used in abrasives and durable surfaces.


Common Pitfalls:

Confusing rock hardness with mineral hardness; assuming marble’s polish implies high hardness. Polishability does not equal scratch hardness.


Final Answer:

Talc

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