Rock Strength and Bonding — Where Are the Strongest Interparticle Bonds Typically Found? Considering the bonding and textures among rock classes, which rocks commonly exhibit the strongest internal particle-to-particle bonds?

Introduction / Context:
Rock strength depends on mineral bonding, fabric, porosity, and cementation. Different rock classes form under different processes which influence how grains are held together, affecting engineering behaviour and erosion resistance.

Given Data / Assumptions:

• Igneous rocks crystallise from melt, often forming interlocking crystals.
• Metamorphic rocks recrystallise under heat and pressure, developing foliation or granular textures.
• Sedimentary rocks are typically clastic or chemical, with grains bound by cement.

Concept / Approach:

Many igneous rocks (e.g., granite, diorite, gabbro) feature an interlocking crystalline texture that yields strong, cohesive bonding with low primary porosity. While some metamorphic rocks are extremely strong (e.g., quartzite, gneiss), foliation planes may introduce anisotropy and potential weakness. Clastic sedimentary rocks (e.g., sandstone, shale) rely on secondary cement (silica, calcite, iron oxides) and can be weak where cement is poor or clay content is high. Thus, as a generalised statement for introductory exams, igneous rocks are credited with the strongest bonds overall.

Step-by-Step Solution:

Compare formation: melt crystallisation vs recrystallisation vs cementation.Evaluate textures: interlocking igneous crystals provide high cohesion.Account for variability but choose the broadly correct class.Select igneous rocks as the common case with strongest bonding.

Verification / Alternative check:

Engineering handbooks and rock mechanics texts report high unconfined compressive strengths for massive igneous rocks relative to many sedimentary units and foliated metamorphic rocks.

Why Other Options Are Wrong:

Metamorphic: Can be strong but may be anisotropic along foliation.Sedimentary: Strength depends on cement; often weaker than crystalline igneous.All similar: False; strength varies widely by class and texture.

Common Pitfalls:

Overgeneralising without considering anisotropy; even strong rocks can have weak planes that control failure.

Final Answer:

igneous rocks