Which property is described by the color of a mineral's powder?

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

Answer: (D)

Streak is the color of a mineral in powdered form, observed by rubbing the mineral across an unglazed porcelain streak plate. This property helps with identification because a mineral’s surface color can vary widely due to impurities, weathering, or coating, making color alone unreliable. The powder color, or streak, tends to be more consistent for a given mineral, providing a useful diagnostic clue. To test streak, you scratch the mineral on the plate and look at the color of the powder it leaves. Keep in mind that some minerals are harder than the plate and won’t produce a streak, and for others the streak may be the same as the surface color, so streak is a helpful hint but not always definitive. The color of the mineral’s powder is what we call its streak.