STREAK

Streak is the color of a mineral when finely powdered – it may or may not be the same as the body color of the mineral (e.g., Hematite).

Use an unpolished porcelain plate.

Drag the mineral across the plate – blow off any excess powder and the remaining color is the streak.

Some minerals are harder than the streak plate and therefore have no streak. Sometime a powder is present because the mineral has powdered the streak plate. Check that the streak plate has not been scratched – blow any powder off the surface and gently run your fingernail across the scratched area to see if an indentation in present.  You can also check with a hard lens.

Streak color is more reliable than body color for mineral identification because the streak of a mineral is usually the same no matter what the body color.