Performing a Streak Test on Rocks

Materials Required:

Streak plate (unglazed porcelain tile)
Rocks or mineral samples for testing
Notebook and pencil for recording observations
Steps Involved:

Introduce the Streak Test: Explain the purpose of the streak test in mineral identification. Emphasize that the streak test reveals the color of a mineral’s powder, which can be different from the rock’s outer appearance.

Prepare for Testing: Provide each student with a streak plate and a selection of rocks or mineral samples to test.

Perform the Streak Test: Instruct students to hold a rock or mineral sample and scrape it gently across the surface of the streak plate. Ensure they apply enough pressure to create a visible streak but avoid excessive force that could damage the plate.

Observe the Streak Color: Have students observe the color of the streak left on the plate. Compare this color to the color of the rock or mineral sample.

Record Observations: Students should record the color of the streak in their notebooks, noting any differences from the rock’s exterior color. Discuss how this information can help in identifying the mineral.

Compare and Identify: If possible, compare the streak test results with known minerals (e.g., fluorite, which always produces a white streak regardless of its color). Use this comparison to help identify unknown minerals.

Discuss Findings: Engage students in a discussion about how the streak test can be a useful tool in mineral identification. Encourage them to think about how this test, along with other tests, contributes to understanding mineral properties.

Review and Reflect: Conclude the activity by reviewing the importance of the streak test and reflecting on how it complements other tests in identifying minerals.