The least efficient property for identifying a mineral is its

• A. Streak
• B. Color
• C. Hardness
• D. Luster

Answer: (B)

Color isn’t a reliable clue for identifying minerals because it can vary a lot within the same mineral and can be shared by many different minerals. Impurities, weathering, and surface coatings can change the color you see on the outside, so color alone can be misleading. In identifying minerals, you rely more on properties that stay consistent across samples: streak, hardness, and luster. The color of a mineral’s powder (streak) is often more diagnostic than surface color, because it’s less affected by surface conditions—for example, hematite may look gray or black, but its streak is a reddish-brown color that helps distinguish it. Hardness tells you how easily a mineral can be scratched, which is a strong distinguishing property (quartz is hard enough to scratch glass, while calcite is not). Luster helps separate metallic from nonmetallic appearances and narrows down possibilities as well. Because color can be deceptive, it’s the least efficient single property for identifying a mineral.