- A list of minerals in order of hardness can be a handy reference. If you determine that a specimen has a hardness of Mohs 4, you can quickly get a list of potential minerals.
- Practice and experience will improve your abilities when doing this test. You will become faster and more confident.
- If the hardness of the unknown specimen is about 5 or less, you should be able to produce a scratch without much exertion. However, if the unknown specimen has a hardness of about 6 or greater, then producing a scratch will require some force. For those specimens, hold the unknown firmly against the table, place the standard specimen against it, press firmly with determination, then holding pressure slowly drag the standard specimen across the surface of the unknown.
- Don’t be fooled by a soft standard specimen producing a mark on a hard unknown. That mark is like what a piece of chalk produces on a blackboard. It will wipe off without leaving a scratch. Wipe your finger across the tested surface. If a scratch was produced, there will be a visible groove. If marks wipe away then a scratch was not produced. Check for the scratch with a hand lens.
- Some hard materials are also very brittle. If one of your specimens is breaking or crumbling rather than scratching, you will have to be very careful while conducting the test. Testing tiny or granular specimens can be difficult.
- Some specimens contain impurities. If the results of your test are not visibly conclusive, or if the information from your test does not conform with other properties, do not hesitate to do the test again. It is possible that a small piece of quartz (or another impurity) was embedded in one of your specimens.
- Don’t be wimpy! This is a very common problem. Some people casually rub one specimen back and forth against another and then look for a mark. That is not how the test is done! It is done with a single, slow, determined motion, with firm pressure, with the goal of cutting a scratch.
- Be careful! When we test we carefully hold the rock being tested so that if the pick slips it will not punch a hole in our finger.
- When we do the hardness test, we place a thick sheet of heavy cardboard or a rubber pad on our table to protect its surface from being scratched.
- This test should be done on a lab table or work bench with a durable surface or a protective covering. Don’t do this type of testing on fine furniture.
- Test tiny particles or grains by placing them between two pieces of an index mineral and scraping them together. If the grains are harder than the index mineral, scratches will be produced. If the grains are softer they will smear.