Streak

Used for many years as a primary diagnostic tool of mineral identification, streak refers to the process of dragging a portion of the mineral across a streak plate, which consists of unglazed porcelain. This produces a powdery trail of a specific color for each mineral specimen, and the color offers a good clue to the mineral’s composition. Two minerals that look quite similar to the eye will often yield very different colored streaks, and this can be a good tool in deciphering the nature of a hand specimen.

Photos

All specimens from the David J. Eicher Mineral Collection; images © David J. Eicher