The Hardness of Metals: A Visual Representation of Mohs Scale

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This metal hardness chart organizes different types of metal using the Mohs hardness scale, a metric used by scientists to determine the scratch resistance of different minerals. With diamond at the top of the scale at a score of 10, elements and alloys can fall along the metal hardness scale from 10 (the most scratch-resistant) to 1 (the softest).

The Mohs Hardness Scale of Metals

We’ve arranged common metals in order of hardness in our handy chart and in this list. Our list includes different kinds of metal from metallic elements like silver to common alloys like steel. Here’s how the Mohs hardness of different metals rank against each other:

  • Boron: 9.3
  • Titanium Carbide: 9.0
  • Tungsten Carbide: 9.0
  • Chromium: 8.5
  • Tungsten: 7.5
  • Vanadium: 7.0
  • Rhenium: 7.0
  • Osmium: 7.0
  • Silicon: 6.5
  • Ruthenium: 6.5
  • Tantalum: 6.5
  • Iridium: 6.5
  • Titanium: 6.0
  • Manganese: 6.0
  • Germanium: 6.0
  • Niobium: 6.0
  • Rhodium: 6.0
  • Uranium: 6.0
  • Beryllium: 6.0
  • Molybdenum: 5.5
  • Hafnium: 5.5
  • Cobalt: 5.0
  • Zirconium: 5.0
  • Palladium: 4.75
  • White Gold: 4.0
  • Steel: 4.0
  • Iron: 4.0
  • Nickel: 4.0
  • Arsenic: 3.5
  • Platinum: 3.5
  • Brass: 3.0
  • Bronze: 3.0
  • Copper: 3.0
  • Antimony: 3.0
  • Thorium: 3.0
  • Aluminum: 2.75
  • Magnesium: 2.5
  • Zinc: 2.5
  • Silver: 2.5
  • Lanthanum: 2.5
  • Cerium: 2.5
  • Gold: 2.5
  • Tellurium: 2.25
  • Bismuth: 2.25
  • Cadmium: 2.0
  • Calcium: 1.75
  • Gallium: 1.5
  • Strontium: 1.5
  • Tin: 1.5
  • Mercury: 1.5
  • Lead: 1.5
  • Barium: 1.25
  • Indium: 1.2
  • Thallium: 1.2
  • Lithium: 1.2
  • Sodium: 0.5
  • Potassium: 0.4
  • Rubidium: 0.3
  • Cesium: 0.2

Our Mohs-scale-of-hardness chart doesn’t necessarily indicate toughness, which is its own metric. Very difficult-to-scratch metals like tungsten may in fact crack easily under pressure, which is what many people experience when wearing that type of jewelry. These metals ranked by hardness can tell us a lot, but not everything, about their properties. For instance, gold is very weak and easy to scratch, at 2.5, but it’s loved by humans for other reasons. For instance, it’s very corrosion-resistant, not very reactive, and makes a great conductor. Meanwhile, for silver, hardness scale metrics really make it seem weak. How hard is silver on the Mohs scale? It’s about the same as gold, at 2.5. And like gold, it’s useful in jewelry, medicine, and science for other reasons. Among other commonly used metals, the brass Mohs hardness is 3.0, along with bronze and copper, which were some of the most important metals, historically speaking.

What Is the Softest Metal?

As our metal hardness scale chart shows, it’s cesium. While other metal types are liquid at room temperature, their solid versions can be quite hard, which is why mercury is so high on our list (at 1.5, about the same as lead). Cesium, meanwhile, even in its solid state, can be cut with a butter knife, with a Mohs hardness of only 0.2. It’s super-reactive, though, so it’s not a fun element to play with!

What Is the Hardest Metal?

Of the elements, the hardest is boron, which is extremely high on the Mohs scale (9.3) and has a crystalline structure. Chromium (8.5) is more abundant and extremely hard. There are other metals that are far more useful from a manufacturing perspective, though: tungsten and titanium. Mohs hardness, while is important, isn’t everything. In addition to having a 6.0 on the scale, titanium is very tough, stronger than standard steel, and has a low density. Tungsten, at 7.5, has a high tensile strength, though it is brittle and easily cracks. Often, both of those elements are mixed with carbon to form carbide alloys that are stronger than the sum of their parts. Alloys often can be quite strong. For instance, for steel, Mohs hardness can vary a great deal depending on the formula of the alloy in question. Your average steel is around 4 or 5, but newer steel alloys can be much higher.

Explore the hardness of metals that are elements, like silver, copper, and nickel, next to alloys like bronze, brass, or titanium carbide and think about this: What are the types of metals used for biomedicine, circuit boards, or even metal buildings? So many of the world’s different types of metals are useful for different purposes, regardless of their rank on the metal hardness scale. We can appreciate the huge variety here on Earth!

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