Which mineral is a sulfide and commonly forms cube-shaped crystals?

Which mineral is a sulfide and commonly forms cube-shaped crystals?

• A. Calcite
• B. Quartz
• C. Gypsum
• D. Pyrite

Answer: (D)

Cube-shaped crystals point to a mineral with a highly symmetric crystal structure, and among common minerals, pyrite stands out. Pyrite is an iron sulfide (FeS2) and is well known for forming metallic, brass-yellow crystals that often resemble tiny cubes. This cube habit comes from its isometric crystal system, where many faces form equal angles, making cube shapes easy to recognize. In contrast, calcite is a carbonate and typically forms rhombohedra, not cubes. Quartz is a silicon dioxide mineral with a hexagonal crystal structure, so its crystals are six-sided prisms rather than cubes. Gypsum is a sulfate and usually forms tabular or prismatic crystals that are not cube-shaped. Because the question asks for a sulfide mineral that commonly forms cube-shaped crystals, pyrite is the best fit.

Cube-shaped crystals point to a mineral with a highly symmetric crystal structure, and among common minerals, pyrite stands out. Pyrite is an iron sulfide (FeS2) and is well known for forming metallic, brass-yellow crystals that often resemble tiny cubes. This cube habit comes from its isometric crystal system, where many faces form equal angles, making cube shapes easy to recognize.

In contrast, calcite is a carbonate and typically forms rhombohedra, not cubes. Quartz is a silicon dioxide mineral with a hexagonal crystal structure, so its crystals are six-sided prisms rather than cubes. Gypsum is a sulfate and usually forms tabular or prismatic crystals that are not cube-shaped. Because the question asks for a sulfide mineral that commonly forms cube-shaped crystals, pyrite is the best fit.