Noun
streak plate (plural streak plates)
(mineralogy) The surface, usually made from unglazed porcelain, across which a mineral is dragged to determine its streak.
Inland Lapidary On the Mohs scale, a streak plate (unglazed porcelain ) has a hardness of 7.0. Source: Internet
The most common way of testing this property is done with a streak plate, which is made out of porcelain and coloured either white or black. Source: Internet