Tile Mohs Scratch Hardness And The ASTM C1895 Test Method

ASTM C1895 is the ASTM test method for measuring the Mohs scratch hardness of ceramic tile, glass tile, and other hard surfaces, using the 1-to-10 Mohs mineral hardness scale first developed by German mineralogist Friedrich Mohs in 1812. According to the ASTM C1895 standard, a surface’s resistance to scratching is determined by visually checking it after an attempt to scratch it with a pick of known hardness. The first edition, C1895-19, covered ceramic tile only. C1895-20 broadened the scope, and ASTM has since published C1895-26 as the current active edition, so confirm which version a given spec sheet references. A higher Mohs rating means better scratch resistance, not immunity to scratching, and ratings vary from one porcelain tile to another. Knowing a tile’s Mohs rating helps buyers set realistic expectations for scratch resistance in high-traffic spaces like kitchens and entryways.

What the Mohs Scale Actually Measures

The Mohs scale runs from 1 to 10, with talc at the soft end and diamond at the top as the hardest known natural material. Each number on the scale corresponds to a mineral that can scratch anything below it and be scratched by anything above it. Quartz sits at 7, corundum (the mineral behind sapphires and rubies) sits at 9, and diamond sits at 10. The scale is ordinal rather than linear, so the jump in actual hardness between each number is not equal. The difference between a 9 and a 10 is far larger in real terms than the difference between a 3 and a 4.

For tile buyers, the practical takeaway is simpler than the mineralogy behind it. A higher Mohs number means better resistance to scratching, not immunity to it. Any surface can still be scratched by a harder material, and Mohs ratings vary from one porcelain product to another, so the specific tile’s spec sheet is the best reference.

A higher Mohs rating means better scratch resistance, not a scratch-proof surface.

ASTM C1895 and How Mohs Testing Is Standardized for Tile

ASTM C1895, the Standard Test Method for Determination of Mohs Scratch Hardness, was first published in 2019 and gives the industry a defined procedure for testing ceramic tile, glass tile, and other hard surfaces. The 2019 edition covered ceramic tile only, and the 2020 edition broadened the scope to glass tile and other hard surfaces.

Under this method, reference picks of known Mohs hardness are drawn across the tile surface. Some picks scratch the surface and some do not, and the tile’s rating is assigned according to the ASTM C1895 procedure based on where that transition occurs. This is a comparative scratch test rather than an indentation-based measurement like the Vickers or Knoop methods.

Because the result is based on a visual observation of the surface after each scratch attempt, Mohs hardness under ASTM C1895 is best understood as a relative ranking against known reference minerals rather than an exact physical hardness figure.

How Mohs Hardness Applies to Tile Selection

Scratch resistance matters most in high-traffic areas. Entryways, kitchens, and hallways see a steady stream of foot traffic, dragged furniture, dropped utensils, and tracked-in grit, all of which can dull or mark a soft surface over time. A tile with a higher Mohs rating is better able to resist the kind of everyday abrasion these spaces see, which is why it helps to check the specific product’s rating rather than assume one for an entire tile category.

Natural stone tile varies on the scale depending on mineral composition. Marble typically rates around 3 to 4, which makes it more prone to scratching than harder stones. Granite and quartzite generally rate higher than marble because they contain harder minerals such as quartz. Because natural stone varies, a single Mohs number should not be treated as universal for an entire stone type, so check the documentation for the specific stone you’re considering. Natural stone is also evaluated with its own wear tests, separate from the PEI ratings used for glazed tile, including standard test methods for stone abrasion under foot traffic.

Mohs hardness, even under ASTM C1895, is specifically about scratch resistance, not overall durability. A tile’s resistance to breaking, staining, slipping, or moisture absorption is governed by separate tests and standards, such as breaking strength, stain resistance, water absorption classifications, and dynamic coefficient of friction testing for slip resistance. A tile can rate well on the Mohs scale while still requiring different considerations for other performance factors. Anyone comparing tile options should look at the full picture rather than relying on a single number.

Reading Mohs Ratings in Context

Even with a standardized test method, a Mohs number is best treated as one data point among several, not a complete performance profile. It’s worth checking what other performance data is available, particularly abrasion resistance ratings like PEI class (tested under ASTM C1027), which measures visible surface wear on glazed tile from foot traffic rather than scratch resistance. Unglazed porcelain is evaluated with a separate deep abrasion test (ASTM C1243) instead.

A Mohs rating on its own is not a determination of suitability for residential or light commercial flooring. Before making that call, review the specific product’s abrasion resistance rating, its manufacturer-stated intended-use classification, and any additional installation guidance for the space in question. This matters even more in unusually abrasive conditions, such as industrial floors or tile exposed to heavy grit and sand, where the manufacturer’s own use classification is the more direct reference point.

Compare Tile Ratings With Our Design Team

A Mohs rating tells you how well a tile surface resists scratching, but it reads best alongside PEI or deep abrasion ratings, water absorption, slip resistance, and the manufacturer’s intended-use guidance. At Nova Tile and Stone, our design team can help you compare these ratings for the porcelain, ceramic, and natural stone options you’re considering. Book a free design consultation or visit any of our showrooms to see the materials in person.

Frequently Asked Questions

What is the Mohs scale used for in tile shopping?

It gives a relative way to gauge how resistant a tile’s surface is to scratching, based on a mineral hardness ranking originally developed in 1812 for comparing raw minerals. For tile, ASTM C1895 provides the standardized test procedure.

Is there an official tile industry standard for Mohs hardness?

Yes. ASTM C1895, the Standard Test Method for Determination of Mohs Scratch Hardness, governs how Mohs testing is performed on ceramic tile, glass tile, and other hard surfaces. It was first published in 2019 for ceramic tile only, and the 2020 edition broadened it to additional materials. ASTM C1895-26 is the current active edition, so check which version a given spec sheet references.

Do all porcelain tiles have the same Mohs rating?

No. Mohs ratings vary from one porcelain product to another, so check the specific tile’s spec sheet. A Mohs rating also does not by itself confirm suitability for a specific residential or light commercial installation. Check the product’s abrasion resistance rating and manufacturer guidance as well.

Does a higher Mohs rating mean a more durable tile overall?

Not necessarily. Mohs hardness only measures scratch resistance. Other factors like breaking, staining, slipping, and moisture absorption are governed by separate tests and ratings, so a complete durability picture requires looking beyond the Mohs number alone.

How does natural stone vary on the Mohs scale?

It varies by stone type and even between individual stones. Marble typically rates around 3 to 4 and is more prone to scratching, while granite and quartzite generally rate higher than marble due to their mineral composition.

About Nova Tile and Stone

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