Gregory Rock

Quick answer: Hardness is resistance to scratching, measured on the Mohs scale; toughness is resistance to breaking or chipping. They

Quick answer: Pleochroism is when a mineral shows different colors viewed along different crystal directions, because its structure absorbs light

Quick answer: Conchoidal fracture is a smooth, curved, shell-like break with concentric ripple marks, named from the Greek word for

Quick answer: Chatoyancy, the cat’s-eye effect, is a single bright band of light that glides across a stone as you

Quick answer: Birefringence, or double refraction, is when a crystal splits a ray of light into two rays that travel

Quick answer: Specific gravity is how heavy a mineral is compared with an equal volume of water. Quartz is about

Quick answer: The streak test identifies a mineral by the color of its powder, made by rubbing it across unglazed

Quick answer: Luster describes how a mineral’s surface reflects light. The main terms are metallic (pyrite, galena), vitreous or glassy

Quick answer: Cleavage is a mineral’s tendency to split along flat planes where its atomic bonds are weakest, producing smooth,

Quick answer: Every crystal belongs to one of seven crystal systems defined by the symmetry of its atomic structure: cubic