ASTM C170 Explained: Compressive Strength Of Dimension Stone

Dimension stone is natural rock that has been quarried and cut to specific shapes and sizes, and no two quarries produce exactly the same material. Mineral content, grain size, bedding planes, and veining all vary from one source to the next, which is why physical testing matters. According to the ASTM C170 standard, the compressive strength of dimension stone is found by loading prepared specimens until they fail, which produces a value in pounds per square inch (psi) that can be used to compare one stone with another. That number appears on many technical data sheets, and knowing how it is produced makes those sheets much easier to read.

What ASTM C170 Measures

Compressive strength describes how much squeezing force a material can resist before it crushes. For stone, that force might come from the weight of a wall stacked above it, foot traffic on a floor, or a heavy object resting on a surface.

ASTM C170 is a test method, not a material specification. It explains how to sample stone, prepare specimens, run the test, and calculate the result. It does not, by itself, say what number a stone must reach. Those pass or fail thresholds live in separate material specifications written for each stone family, such as granite, marble, quartz-based stone, and travertine. Each of those specifications points back to C170 as the method for measuring compressive strength.

This distinction matters when you read a data sheet. A compressive strength result tells you how the stone performed in the test. Whether that result is high or low depends on which stone family the material belongs to and what that family’s specification requires.

How the Test Is Performed

A laboratory cuts specimens from the stone being evaluated, measures them precisely, and places them in a compression machine. The machine presses down on each specimen with steadily increasing force until it breaks. The load at the point of failure is divided by the specimen’s loaded area to calculate strength in psi.

Moisture and orientation are both built into the procedure. For the dry condition, specimens are oven-dried for at least 48 hours at 140°F, with weights checked at the end of that period to confirm the stone has stopped losing moisture. Wet specimens are soaked in water for 48 hours before testing. Running both conditions shows how the stone’s strength changes when it holds water, which is useful information for outdoor paving, wet areas, and any surface that sees regular moisture.

Orientation matters because many stones have a rift. In ASTM terminology, the rift is the direction along which a stone splits most easily, and in layered stones it generally follows the bedding. A stone can respond differently when force is applied parallel to the rift compared with perpendicular to it. For this reason, the test is run in both directions, and results are reported for each.

Put together, a full set of results often covers four combinations: wet and dry, each tested parallel and perpendicular to the rift. When you see a single compressive strength value on a data sheet, it is worth asking which of those conditions it represents.

Published Minimums by Stone Type

Each stone family has its own minimum compressive strength in its ASTM specification. The published minimum compressive strengths for three common stone families are 19,000 psi for granite under ASTM C615, 7,500 psi for marble under ASTM C503, and 7,500 psi for travertine intended for exterior applications under ASTM C1527.

For quartz-based stone, ASTM C616 sorts material into three types by free silica content: sandstone (Type I), quartzitic sandstone (Type II), and quartzite (Type III). The minimum for Type III quartzite is 20,000 psi, as shown in a university design standard that lists the quartz-based stone minimums measured perpendicular to the grain. That minimum applies to stone that meets the Type III classification, not automatically to every stone sold under the name quartzite.

A few points help put these figures in context. First, they are minimums, not typical values. Second, the numbers differ widely between families because the rocks themselves are different. Granite is an igneous stone formed from cooled magma, marble is a metamorphic stone, and travertine is a sedimentary stone. Comparing a marble result directly against the granite minimum would not tell you much. Third, strength can vary between stones of the same type, and even within a single classification, so test data for the specific stone you are considering is more useful than a general category figure.

Standards are also revised over time. If a project depends on a specific threshold, the current edition of the relevant specification is the place to confirm it.

What Compressive Strength Tells You, and What It Does Not

Compressive strength is a helpful indicator, but it describes only one kind of stress. Stone in a home or building is often loaded in other ways.

A large wall panel or a stone piece spanning an opening, such as a lintel, is stressed by bending rather than crushing. A floor in a busy entry is affected by wear from foot traffic. An outdoor patio in a cold climate faces freezing and thawing. Each of these conditions has its own test. Laboratories commonly run compressive strength alongside flexural strength, abrasion resistance, and freeze/thaw tests, and one industry lab’s standard package for compressive strength uses 20 specimens split across the wet, dry, parallel, and perpendicular conditions.

Slip resistance is a separate measurement as well. It is evaluated under ANSI A326.3, the test method for measuring the dynamic coefficient of friction (DCOF) of hard surface flooring. The standard sorts products into use categories such as interior dry, interior wet, and exterior wet, which is information a compressive strength result cannot provide.

For this reason, a high C170 result does not mean a stone is suited to every use. A stone with strong compressive figures may still need careful evaluation for a thin, wide installation where bending strength matters more, or for an exterior setting where absorption and weathering come into play. The most complete picture comes from reading C170 results together with absorption (ASTM C97), flexural strength (ASTM C880), modulus of rupture (ASTM C99), and abrasion resistance data.

How to Use C170 Data When Choosing Stone

If you are comparing stones for a project, a few habits make test data more useful.

Compare like with like. Line up results from the same test condition. A dry, perpendicular result and a wet, parallel result from two different stones are not a fair comparison.

Check the stone family. Confirm which specification applies before judging a number. A marble result that sits comfortably above the marble minimum is meeting its own standard, even if the figure is lower than a typical granite result.

Confirm the data exists. Not every stone on the market comes with a full set of ASTM results. When test data is not available for a stone, independent laboratories can run the tests and provide a report.

Match the data to the application. Indoor wall cladding, a kitchen floor, and an exterior walkway place different demands on stone. Compressive strength is one important property to review for stone that carries direct load, such as flooring, pavers, and steps. Those uses also call for attention to flexural strength, abrasion resistance, thickness, and the loads expected in use.

Here is how this applies to the natural stone families we carry at Nova Tile and Stone. Our granite and quartzite are suitable for indoor and outdoor use on floors, walls, and fireplaces, and both are UV resistant, which makes their compressive data relevant for patios and walkways as well as interiors. Our travertine is also suitable for indoor and outdoor floors, walls, and fireplaces, and the exterior minimum noted above is the figure to compare against for outdoor use. Our marble is suitable for indoor floors, walls, and fireplaces, where its compressive strength is one of several properties to review alongside its finish and care needs.

A Note on Engineered Quartz and Porcelain

ASTM C170 and the specifications that reference it are written for quarried natural stone. The quartz-based dimension stone specification, for example, excludes artificially aggregated units made from fragments, as well as crushed and broken stone.

Porcelain tile is a manufactured product rather than quarried stone, and it is covered by its own ANSI specifications, including standards for ceramic tile and for gauged porcelain tile panels and slabs.

This means the natural stone minimums noted above are not the right benchmark for engineered quartz or porcelain. For those materials, the manufacturer’s own technical data and the standards it lists are the place to look.

Frequently Asked Questions

What does ASTM C170 test?

ASTM C170 is the standard test method for measuring the compressive strength of dimension stone. It covers how specimens are sampled, prepared, loaded, and calculated, and it reports the result in psi or MPa.

Is a higher C170 number always better?

Not necessarily. A higher number means the stone resisted more crushing force in the test, but compressive strength is only one property. Flexural strength, absorption, abrasion resistance, and slip resistance can matter just as much, depending on where the stone is used.

Why are there different results for wet and dry conditions?

Many stones respond differently when they hold water. Testing both conditions shows how strength may change in damp or outdoor settings, which helps when comparing stones for those areas.

Does ASTM C170 apply to engineered quartz or porcelain?

The method and the related stone specifications are written for natural quarried stone. Engineered quartz and porcelain are manufactured products, so their performance is best reviewed through the manufacturer’s technical data and the standards written for those materials.

Where can I find C170 results for a specific stone?

Quarries and suppliers often publish technical data sheets that include C170 results along with other ASTM test values. When reviewing one, check the test date, the laboratory, and which conditions the reported value represents. If no results are available, an independent lab can run the tests.

Find Stone That Fits Your Project

Reading a test report is easier when you can see and feel the stone it describes. At Nova Tile and Stone, our team can walk you through the slabs, tile, pavers, and exterior stone we carry and talk through how a material might suit the space you have in mind. We offer free design consultations, as well as a sample program for tile. Visit a Nova Tile and Stone showroom to start comparing options in person.

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