Calculator Scratch

A simple, effective calculator scratch tool to compare material hardness.

Select two materials to see the result.

Material A Hardness–

Material B Hardness–

Hardness Difference–

What is a Scratch Hardness Calculator?

A calculator scratch tool, in the context of material science, is designed to determine the relative hardness of two materials. Specifically, it predicts whether one material will visibly scratch another when they are rubbed against each other. This is not about building a calculator from scratch, but about the physical act of scratching. The primary principle used is the Mohs scale of mineral hardness, a qualitative ordinal scale that characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. Our calculator scratch tool simplifies this comparison for you.

This calculator is essential for geologists, material scientists, jewelers, and hobbyists who need a quick way to identify or compare minerals and materials. By understanding which material scratches another, one can deduce their relative positions on the Mohs scale, a foundational concept in mineralogy. For a deeper analysis, check out our guide on the Mohs hardness scale.

The Formula and Explanation for Scratch Hardness

The “formula” for a calculator scratch test based on the Mohs scale is a simple comparison, not a complex mathematical equation. It is based on a fundamental principle:

If Hardness(Material A) > Hardness(Material B), then Material A will scratch Material B.

The Mohs scale is an ordinal scale, meaning it ranks materials from softest (1) to hardest (10). It does not provide a linear or proportional measure. For instance, while Diamond (10) is one number higher than Corundum (9), it is many times harder in absolute terms. Our calculator automates this comparison for you.

Variables Table

The variables involved in a Mohs hardness scratch test.

Variable	Meaning	Unit	Typical Range
Hardness(A)	The Mohs hardness value of the scratching material.	Mohs (Unitless Scale)	1 – 10
Hardness(B)	The Mohs hardness value of the material being scratched.	Mohs (Unitless Scale)	1 – 10
Result	The outcome of the scratch interaction.	Qualitative (Yes/No/Neutral)	N/A

Practical Examples

Understanding the concept is easier with practical examples. Here are a couple of common scenarios you might encounter when using a calculator scratch test.

Example 1: Quartz vs. Steel

• Input (Material A): Quartz (Hardness: 7)
• Input (Material B): Steel File (Hardness: ~6.5)
• Units: Mohs Hardness
• Result: Quartz will scratch the Steel File. This is a common field test to distinguish quartz from softer minerals.

Example 2: Apatite vs. Glass

• Input (Material A): Apatite (Hardness: 5)
• Input (Material B): Window Glass (Hardness: ~5.5)
• Units: Mohs Hardness
• Result: Apatite will NOT scratch the Window Glass. This helps mineralogists narrow down the identity of an unknown sample. Interested in material properties? Our density calculator can be a useful next step.

How to Use This Scratch Hardness Calculator

Using our calculator scratch tool is straightforward. Follow these simple steps for an accurate result.

1. Select Material A: From the first dropdown menu, choose the material you will use to perform the scratching. This is your “scratcher”.
2. Select Material B: In the second dropdown, choose the material that will be the surface you are testing.
3. Interpret the Results: The calculator will instantly update. The primary result tells you in plain language whether Material A scratches Material B.
4. Review Intermediate Values: The display shows the exact Mohs hardness for both selected materials and the difference between them, providing more context.
5. Analyze the Chart: The bar chart provides a quick visual reference to how the two materials compare in hardness.

For more advanced analysis, a material scratch test guide can provide details on professional testing procedures.

Key Factors That Affect Scratch Hardness

While the Mohs scale provides a great reference, several factors can influence the outcome of a real-world scratch test. Understanding these is key to accurate assessment.

• Crystallographic Direction: Some minerals exhibit different hardness on different crystal faces or directions (anisotropy). Kyanite is a classic example.
• Material Purity: Impurities or inclusions within a mineral can alter its bulk hardness, making it softer or harder than a pure sample.
• State of Aggregation: A massive, solid piece of a mineral will appear harder than a granular or powdered form of the same mineral.
• Applied Pressure: While the Mohs test is qualitative, applying insufficient force may not produce a scratch even if the material is harder. Consistent, firm pressure is needed.
• Twinning and Fractures: Pre-existing micro-fractures or crystal twinning can create weak points, making a material easier to scratch along those lines. Explore more in our article on introduction to metallurgy.
• Weathering/Alteration: A weathered surface on a mineral is often softer than its fresh, unexposed interior. Always test on a fresh surface if possible.

Frequently Asked Questions (FAQ)

1. Is the Mohs scale a quantitative measure of hardness?

No, it is a qualitative, ordinal scale. It ranks minerals based on relative scratch resistance but does not show that a mineral with hardness 6 is twice as hard as one with hardness 3. Absolute hardness scales like Vickers or Knoop are quantitative. This is a common point of confusion when people search for a what scratches what calculator.

2. What does it mean if two materials have the same hardness?

If two materials have the same Mohs hardness, they will be ineffective at scratching each other. They may abrade or dull each other’s surface, but a clean scratch will not be formed.

3. Why isn’t there a unit switcher on this calculator?

The Mohs scale is a single, universally accepted (though relative) standard. The values are unitless rankings from 1 to 10, so there are no alternative units like metric or imperial to switch between.

4. Can I test materials not on the list?

This calculator is limited to the materials provided. However, you can use the known hardness values of common objects (like a fingernail at 2.5 or a copper penny at 3.5) to test unknown materials yourself and compare them to the values in our mineral hardness guide.

5. What is the hardest material?

On the Mohs scale, Diamond is the hardest at 10. It can scratch all other materials on the scale. No common natural material can scratch a diamond (though diamonds can scratch each other).

6. What if the result is a very small positive difference?

Even a small difference (e.g., 6.5 vs. 6.0) means the harder material should scratch the softer one. However, the scratch may be faint and require careful observation or a hand lens to see clearly.

7. Does the shape of the scratching point matter?

Yes. A sharper point concentrates force over a smaller area, making it more effective at scratching. For consistent results, try to use a pointed edge of the testing material.

8. What is the difference between hardness and toughness?

Hardness is resistance to scratching or surface indentation. Toughness is resistance to breaking, chipping, or cracking under impact. A material like diamond is extremely hard but can be brittle (not tough), while a material like jade is less hard but very tough. Our friction coefficient calculator may also be of interest.