The property of a mineral that shows the color of its powder is called streak.

Here's why it's important:

* Color can be deceptive: A mineral's external color can be influenced by impurities or weathering, making it unreliable for identification.

* Streak is consistent: The streak color is more consistent and less affected by surface alterations.

* Streak test: To determine streak, you rub the mineral across a streak plate (unglazed porcelain). The color of the powder left behind is the streak.

Example: Hematite can be red, brown, or black depending on its form. But its streak is always reddish-brown.