Which Rocks term is correctly associated with identifying feature: “so porous that some pieces can float on water”, and also with “used as an abrasive and lightweight aggregate”?

Correct Answer: Option C — Pumice. Pumice is correct because it is so porous that some pieces can float on water. Pumice is also associated with used as an abrasive and lightweight aggregate. A further identifying fact is that Pumice is so porous that some pieces can float on water. Another useful fact is that Pumice is associated with used as an abrasive and lightweight aggregate. Why the other options are incorrect: Option A — Obsidian: It is glassy texture with conchoidal fracture and is associated with historically used for sharp cutting tools; those are the identifying facts of Obsidian. Option B — Sandstone: It is often shows bedding layers and is associated with commonly used as a building stone; those are the identifying facts of Sandstone. Option D — Limestone: It is reacts with dilute acid and is associated with a major raw material for cement; those are the identifying facts of Limestone. Exam Takeaway: Link Pumice with “so porous that some pieces can float on water” and “used as an abrasive and lightweight aggregate” for quick revision.