Three Stone Tests Everyone Should Know About

It seems like there is a test for nearly everything. And the stone industry is no different. There are a number of natural stone types. Claims are made by sales professionals and slab yards at the time of selection. Additionally, each natural stone is unique so getting an idea of some basic characteristics of a given stone can help consumers inform themselves. Knowing some basic facts about a particular stone can reveal inconsistencies, misinformation, and even completely incorrect naming and maintenance requirements. The three tests that we will describe in this article will help accurately determine facts that guide consumers (and professionals) to proper conclusions regarding various stone slabs. Let's get into three stone test everyone should know about.

Three Helpful Stone Tests

1. Testing Hardness
2. Testing Absorption
3. Testing Composition

Different test for Different Purposes

There are many types of information that people want to know about when it comes to stone; natural stone in particular. Because of this you will find many kinds of stone tests. Some of the information that is produced from these tests is technical and some general.

• Wear Rate
• Absorption
• Compressive Strength
• Crushing Strength
• Density
• Flexural Strength
• Hardness
• Crystalline Potential
• Impact Resistance
• Abrasion Resistance
• Bond Strength

Even though there are a number of different stone tests performed by various professionals for many purposes, there are a handful that everyone should be familiar with. Don't worry, you don't have to be an engineer to make practical use of the tests we are going to describe in this article. True, there is a benefit to testing stone for the purpose of measuring its characteristics. But the ones we are going to look at here provide information that is often needed by consumers.

Scratch Test - Determining A Stone's Hardness

The first test that everyone should know about is what we'll call a "scratch test". This test is designed to measure the hardness of the stone being tested. Each type of stone registers at a different hardness level on the Mohs scale of mineral hardness. Because some rock types look similar it can be challenging at times to differentiate one type of stone from another. This test gives the tester an idea of how hard the stone is, and this can help in making the final determination. So how is a scratch test done?

Performing the Test

One of the simplest ways to perform a hrdness test on a natural stone is to put a sharp piece of the stone head-to-head with a substance of which you know the hardness. Window glass registers at 5.5 on the Mohs hardness scale so it is pretty good candidate that is readily available for most people.

Take a sharp piece of the stone that you want to test and firmly press a sharp point of it against the glass and drag it across the surface. As the name of the test implies, you are simply trying to "scratch" the glass with the stone. Can you scratch a groove into the glass that does not rub off? Or is the stone being pulverized as you drag the point across the glass? You will feel and likely hear the glass scratching if the stone is hard enough. If the stone is not hard enough, you will feel and hear less resistance as you perform the test.

Measuring The Results

The results are simply enough to measure. If the glass scratched, the stone is harder than 5.5. If the stone crumbles, it is softer than 5.5. Each kind of stone has an average hardness and can be looked up pretty easily but here are some of the popular ones.

Why Hardness is Good to Know

One reason it is good to know the hardness of a countertop material is that it gives you an idea of the stone's durability. The harder the stone is the more resistant it will be to scratches.

Another benefit to learning a stone's hardness is that it can distinguish one stone from another. As mentioned above, each stone type has a different hardness. So two stones that look similar - like quartzite and marble for example - can be distinguished from one another.

It is easy to see why it is good to know about the scratch test (a.k.a. hardness test). But it is just one of the three stone tests everyone should know about. There are two others.

Water Test - Testing Porosity Through Absorption

The second stone test we will consider is the "water test". A water test, also referred to as the "absorption test". This test is a very practical way to determine how quickly a stone absorbs liquids at a given time.

Performing the Test

Conducting a water test is pretty simple and can be done by anyone at anytime. The process consists of 3 steps. They are:

1. Pour water on the surface of the stone.
2. Observe the water for a few minutes.
3. Determine the rate of absorption.

If you are thinking, "that sounds easy", we agree. The faster the stone absorbs the water, the more absorbant it is. And the absorbancy of a stone, tells you some specific things.

Observing the Results

The results of this easy test to check absorbancy will vary from stone-to-stone. In fact the same natural stone will vary depending on factors that we will consider momentarily. But first let's look at how to understand the results.

Natural stone is porous and all natural stone absorbs liquids. As mentioned above, the porosity of a stone is directly related to the rate at which liquids are absorbed. So, the faster it absorbs water, the more porous it is. And, the absorbancy rate of a given stone is good to know.

Why Knowing Absorbancy Is Important

There are a number of liquids that are used in households where stone countertops have been installed. Some of these substances can stain a natural stone surface. Hence, the faster a stone countertop soaks up a liquid, the more apt it is to stain. Knowing the rate at which a countertop will absorb liquid gives you an idea of how stain resistant the stone is. Does that mean that the absorbancy cannot be affected? No. Let's see why that is the case.

Even though all natural stone slabs absorb liquids to one degree or another, the absorption can be slowed down by using a natural stone sealer. There are many from which to choose. Each one will offer a particular niche benefit, but many will work on a variety of materials. So, it is good to get an idea of which one is recommended for your type of stone.

Knowing about the water test is vital if you want to be able to determine when and how often to apply a sealer to a particular stone countertop. Sealers are not permanent and they can break down when the incorrect cleaners are used to clean them. Knowing how to conduct and understand an absorbancy test (or water test) afford you the ability to monitor the state of your countertop at any given time.

Acid Testing - A Test Revealing Composition

The last of the three stone tests that everyone should know about is what we will refer to as an "acid test". Also called a mineral test, this test allows you to test for a specific mineral using a simple method.

Performing the Test

Before we get into how to do the test, we need to make something very clear: this test will damage certain kinds of stone so do not do this test on a part of the stone you intend to use. Conducting an acid test on a small corner of a stone or on the back of the slab is the safest.

Performing an acid test is simply a matter of exposing a part of the stone to an acidic liquid and observing what happens. The test need not take a long time and can be done with normal household liquids. One good one is vinegar.

The Benefit of Knowing About the Acid Test

This test, as mentioned above, reveals something about the mineral content of the stone on which it is conducted. To be more specific, it lets you know whether the stone in composed of calcite, or calcium carbonate. Calcium carbonate reacts with acids. An acidic liquid that is poured on a stone containing calcite disolves the calcite. Thus, the stone is in a sense "eaten" away. This is something that you want to know before you select a countertop material for say, your kitchen.

Being able to tell if a stone contains calcium carbonate is very practical because it can help to distinguish two stones that are similar in appearance. This test when performed in conjuction with the scratch test (mentioned earlier) can help you to identify a true quartzite slab. Since true quartzite contains no calcite, this test willnot harm a quartzite slab. However, it will have an affect on marble (which strongly resembles quartzite).

In conclusion, knowing about thre simple tests that just about anybody can perform; 1) scratch test, 2) water test, and 3) acid test, will equip you. Knowing about these tests allows you to know what knidn of stone you own (or are lookng to purchase) and guides you in determining how best to care for that stone countertop.