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Marble & Limestone

Comparing Limestone With Marble

You don't have to look very long to find that many architectural surfaces are made of marble. And if you inspect a number of projects, you will find a good deal of limestone as well. Looking closely at structures made from these materials will reveal that these stones are similar in composition. This begs the question, "what is the diffreence betwen limestone and marble?" In this article, we will take up the task of comparing limestone with marble. We will touch on several points regarding limestone and marble stone. So let's get right into our look at limestone vs. marble.

What is Limestone?

In general terms, limestone is a sedimentary rock that forms naturally and can be found in many places. However, Wikipedia.org talks about this natural stone in more specific terms. In the page for limestone, that reference makes the following statement:

Limestone is a common type of carbonate sedimentary rock. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO3). Limestone forms when these minerals precipitate out of water containing dissolved calcium. This can take place through both biological and nonbiological processes...

So, limestone is a naturally occurring stone that is primarily made up of calcium carbonate. One key point to note as it regards our topic here is that limestone is sedimentary. This is important as we will see later in our consideration of how limestone compares to marble.

Properties of Limestone

Most limestone is a variation of one of the following colors:

  • White
  • Cream
  • Beige
  • Light Gray
  • Blue
  • Yellow
  • Brown
  • Gray
  • Red
  • Dark Gray
  • Black

Even though the substance of which limestone is primarily composed of is white, "impurities" in the material cause other colors to be mixed in. Thus, the final color of the stone becomes a shade of one of the colors listed above.

Susceptible to Acids

One of the traits associated with calcium carbonate is that it reacts with acid. In fact, some antacid medications are calcium carbonate tablets. When calcium carbonate is in the presence of acid, it neutralizes the acid. But not without cost. The acid disolves the calcium carbonate during the reaction. This means that a stone labeled as limestone can be tested using an acid test. And, vice versa, a stone that is labeled as some other material that is not composted of calcium carbonate can be tested as well. If it reacts with acid, then the stone is mislabeled.

Limestone is a very common type of rock and is used for many purposes in daily living. But what about its counterpart?

What is Marble?

Comparing marble with limestone using a familial relationship would lead many to use a parent-child relationship or maybe a sibling relationship. This is because natural marble is a metamorphic rock. Metaporphic rock is defined on Lustro Italiano the following way:

Rock altered in appearance, density, crystalline structure, and in some cases, mineral composition, by high temperature and intense pressure. Includes slate derived from shale, quartz based stone from quartzitic sand, and true marble from limestone.

Notice that one of the three pairs of rock mentioned in the definition is marble and limestone. That's right. Marble is limestone that has been transformed into a different rock through the metamorphic process.

Limestone and Marble Commonalities

Since marble was limestone before it became transformed, it stands to reason that it would have some smilarities with marble. And it does. For example, the colors of marble are similar to those of limestone. Additionally, marble reacts to acid the same way that limestone does.

Limestone and marble both register on the low end of the Mohs scale of mineral hardness. Each of these is a relatively soft stone and may be shaped easily using the proper tools. We recommend using a diamond blade for marble to cut these materials. Using a blade that is not made for cutting soft stone can prove to be challenging and make the job more difficult.

Differences Between Limestone and Marble

At this point in the discussion, you may be asking, "If these materials are composed of the same minerals, then what is the difference?" That is a good question. And in reality, you can actually find some limestone salbs actually labeled with the term marble (or a marble name). But let's look at what the technical difference is between these natural stone materials.

Looking again at the definition above that we took from the Lustro Italiano website, you will notice that in addition to the appearance, it says that metamorphic change can affect the density and the crystalline structure of the rock. When the heat and pressure that causes the metamorphasis acts on limestone, it causes the stone to recrystallize, forming a different crystalline structure from what it had previously.

So, as we have seen, limestone and marble are similar in composition. But they are actually different kinds of natural stone. Limestone, being a sedimentary rock, and marble being a metamorphic rock. And even though these materials do share some traits in common, they have enough differences that they are classified as different types of rock even though you will likely find that some limestone is labeled as marble in the stone industry.