How is the streak test performed?
See a DEMONSTRATION VIDEO here.
from the mineral to be tested, the only necessary tool is a streak plate, which
usually consists of an unglazed piece of white or black porcelain.
To conduct the test, simply drag the mineral
across the porcelain plate, exerting enough force to leave a powdered line on
the plate. In principle, this is
analogous to a graphite pencil leaving its mark on a piece of paper.
As you can see, the streak test is an easy one to
conduct, but there are a few additional details to remember.
1. Never use a weathered part of a
mineral when conducting the test.
2. Remember that minerals with a MOHS
hardness of 7 or more can’t be streak tested because they are harder than the plate, and will not leave a streak.