Final answer:
The true color of a mineral as seen in its powdered form is called its streak, which is revealed through a streak test on a ceramic plate and is imperative for mineral identification, especially for metallic minerals.
Step-by-step explanation:
The true color of a mineral as seen in its powdered form is called its streak. The streak test involves dragging the mineral across an unglazed porcelain plate and observing the color of the mark it leaves, which represents the mineral in its powdered form. This method is particularly valuable for mineral identification because the color of a mineral can be influenced by impurities and surface conditions, leading to mistaken identification. However, when a mineral is powdered, these factors do not significantly affect its color, providing a more accurate representation of the mineral's inherent color. For instance, the mineral hematite will leave a red-brown streak, even though its crystal form can be black or metallic gray. It is essential to understand that streak is a diagnostic property primarily for metallic minerals, as non-metallic minerals typically have a white streak or a streak color similar to their natural appearance.