True or false: If a rock has a certain color, its streak (the mark it leaves when rubbed on a streak plate) will be the same color as the rock.
False. A rock or mineral’s surface color can differ from its streak color because surface color can be affected by impurities and weathering. The streak is the color of the mineral’s powder and is often more reliable than the outside color for identification.
What this question is really testing
This is asking about the difference between a mineral’s visible surface color and its streak, which is the color of the powdered mineral left on an unglazed porcelain streak plate.
Why the statement is false
A mineral can look one color on the outside but leave a different-colored streak. That is because the surface color can change due to impurities, oxidation, or weathering, while the streak shows the mineral’s true powder color.
Quick example
Hematite can look metallic gray or reddish-brown, but its streak is typically reddish-brown. So even when the mineral’s surface color varies, the streak can stay consistent.
When streak might match the surface color
Sometimes they do match, especially for minerals that have a consistent color and are not weathered, but it is not a rule you can count on. That is why the true or false statement is false.
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