Which property describes the color observed when a mineral is dragged across a porcelain plate to produce a powder?

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

Answer: (B)

Streak is the color of a mineral in powdered form, obtained by rubbing the mineral across a rough, unglazed porcelain plate. This test focuses on the powder color, which often remains constant even if the mineral’s surface color is affected by surface coatings or weathering. Because many minerals look alike in hand sample but leave different-colored powders, the streak helps identify them more reliably. A mineral might appear a certain color on its surface yet produce a white, gray, red, or green powder, revealing its true streak color.

Hardness tells you how easily the mineral is scratched, not the color of its powder. Luster describes how light reflects off the surface, not the color of the powdered form. Tenacity describes how the mineral behaves under stress (brittle, ductile, malleable), again not about the powder color.