Scratch Tests

Test hardness with a fingernail, a copper coin, glass, and a steel file.

Warm-up, learn, try it together, practice, then a quick check. About 15 minutes.

What children learn in Level 4

Hardness is how easily something can be scratched. A harder thing can scratch a softer thing, but not the other way around.
Rock hounds test hardness with everyday things: a fingernail, about 2½; a copper coin, about 3½; glass, about 5½; and a steel file, about 6½.
If a coin can scratch a mineral, but a fingernail can't, the mineral is harder than 2½ and softer than 3½.
Try it with a grown-up: gently try to scratch a few rocks with a fingernail, then a coin. Which rocks are hardest? Never scratch anything valuable, and keep glass for a grown-up to hold.

Georgia Standards of Excellence in Science:

S3E1.a — Ask questions and analyze data to classify rocks by their physical attributes (color, texture, luster, and hardness) using simple tests. (Clarification statement: Mohs scale should be studied at this level. Cleavage, streak and the classification of rocks as sedimentary, igneous, and metamorphic are studied in sixth grade.)