Streak PlateThe "streak test" is a way of determining the color of a mineral in powdered form. A specimen of the mineral is placed against a piece of unglazed porcelain plate (known as a streak plate) and scraped across the surface of the plate. If a powdered residue is left behind the color of that powder is known as the mineral's "streak color". The observer must determine if the mark left on the streak plate is a genuine "powder" or if it is composed of granules of broken fragments.
These streak plates are approximately 2" x 2" in size and about 3/16" thick. They are a good size for classroom, field and laboratory use. The black plate allows for easier examination of a white mark to determine if it is a powder or if it is granules or broken fragments.