Tile Mohs Scratch Hardness Standard: ASTM C1895-20

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. This article describes the framework established under ASTM C1895-20; ASTM has since published C1895-26 as the current active edition, so confirm which version a given spec sheet references. Under the test, a series of reference picks of known Mohs hardness are drawn across the tile's surface, and the rating is assigned per the ASTM C1895 procedure based on which picks scratch it and which do not. Porcelain tile typically scores 6 to 7, at or just below quartz (7) on the same scale, and since sand and household dust commonly contain quartz, that rating does not make porcelain immune to everyday scratching. 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 sitting at the soft end and diamond anchoring 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, which means 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 2 and a 3.

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, since porcelain's typical 6 to 7 range sits at or just below quartz (7), a common component of sand and everyday grit. Finish also plays a role within that range. Matte and unglazed porcelain tend to sit at the higher end, and their texture helps camouflage minor scratches, while polished porcelain is often reported as somewhat softer, with its glossy surface making any scratches more visually noticeable.

What the Mohs Scale Actually Measures

ASTM C1895 and How Mohs Testing Is Standardized for Tile

A Mohs number on a tile spec sheet used to be treated as an informal, comparative figure rather than the result of a standardized lab test. ASTM C1895, the Standard Test Method for Determination of Mohs Scratch Hardness, changed that by giving the industry a defined procedure for testing ceramic tile, glass tile, and other hard surfaces. The standard was first introduced specifically for ceramic tile before being broadened to additional hard surface types.

Under this method, a series of reference picks with known positions on the Mohs scale are drawn across the tile surface under controlled conditions. 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, reported as a whole or half-integer value. This is a comparative scratch test rather than an indentation-based measurement like the Vickers or Knoop methods, which makes it well suited to brittle, glazed, or vitrified surfaces like tile.

Because the test relies on visual assessment rather than a precise mechanical force reading, results can be influenced by surface preparation, operator interpretation, and material variation. 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 Mohs rating in the 6 to 7 range, which is typical for porcelain, holds up well against the kind of everyday abrasion these spaces see.

Natural stone tile varies more widely on the scale depending on mineral composition. Marble, for example, is a softer stone and sits lower on the Mohs scale than porcelain, which is one reason marble floors are more prone to physical scratching and surface wear in heavy-use areas. Granite and quartzite, by contrast, tend to rate higher because of their mineral makeup, which is part of why they are often recommended for durability-focused applications.

It is worth noting that Mohs hardness, even under ASTM C1895, is specifically about scratch resistance, not overall durability. A tile's resistance to cracking, chipping, staining, or moisture absorption is governed by separate tests and standards, such as breaking strength, water absorption classifications, and impact resistance ratings. A tile can rate well on the Mohs scale for scratch resistance 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, which measures wear from foot traffic rather than scratch resistance and is standardized separately for glazed tile surfaces.

A Mohs rating in the 6 to 7 range is not, by itself, 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.

Conclusion

The Mohs scale offers a widely recognized way to think about how well a tile surface resists scratching, and ASTM C1895 provides a standardized method for measuring it on ceramic tile, glass tile, and other hard surfaces. Its 1 to 10 range, from soft talc to diamond, gives shoppers a useful frame of reference, but a rating like porcelain's typical 6 to 7 describes relative scratch resistance, not immunity to it, and does not by itself confirm suitability for a given space. Because the scale measures scratch resistance rather than overall durability, it is best read alongside other performance data, such as PEI ratings, water absorption classifications, and the manufacturer's intended-use guidance, rather than as a standalone measure of tile quality.

Frequently Asked Questions

What is the Mohs scale used for in tile shopping?

It gives a standardized 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.

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 originally introduced specifically for ceramic tile before being broadened to additional materials. The edition discussed in this article is C1895-20; ASTM C1895-26 is the current active edition, so check which version a given spec sheet references.

What Mohs rating does porcelain tile typically have?

Porcelain tile generally falls in the 6 to 7 range on the Mohs scale. This provides meaningfully better scratch resistance than a softer material, though it 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 cracking, chipping, staining, 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 compare to porcelain on the Mohs scale?

It varies by stone type. Softer stones like marble typically rate lower than porcelain and are more prone to surface wear, while harder stones like granite and quartzite often rate higher due to their mineral composition.

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