Answer: streak.
Explanation: Streak refers to the color of the fine powder of a mineral. It is often more consistent and reliable than the color of the mineral itself, which can be affected by impurities. To test the streak, you can rub the mineral against a streak plate or an unglazed porcelain tile to produce a powdered residue. Different minerals leave different colored streaks, allowing geologists and mineralogists to identify minerals more accurately.
Other essential characteristics for mineral determination include hardness, cleavage, fracture, luster, and crystal form. Collectively, these properties provide valuable clues for identifying minerals in the field of mineralogy.