Streak

Definition

The colour of a mineral when powdered and observed against an unglazed white porcelain plate.

Test

Rub the mineral across an unglazed white porcelain plate and describe the colour of the powder left on the plate, i.e. the streak.

Notes: This is often a useful property for identifying opaque minerals which can have a streak colour that differs markedly from their apparent colour. For example pyrite is gold coloured, but its streak is greenish-black.

Most pale coloured or transparent to translucent minerals have a non-determinative white streak.

Minerals with a hardness of more than 6.5 will not exhibit a streak as they are harder than a piece of unglazed porcelain.