The color of a mineral's powder is its?

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

Answer: (A)

Streak is the color of the powder produced when a mineral is rubbed on an unglazed porcelain plate. This test is useful because the powder color is often more consistent than the mineral’s surface color, which can vary due to impurities, weathering, or coatings. Some minerals show the same surface color but leave a different powder color, making streak a helpful diagnostic tool. The other terms describe different properties: luster is how light reflects from the surface, hardness is how easily the mineral can be scratched, and transparency is how much light passes through. So the color of a mineral’s powder is its streak.