Posted by Teresa Wirtz on 2/1/2019 to
News
How is the streak test performed?
Aside 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.