Granite vs. Marble - A Comparison

Two of the most prominent natural stones used in architecture are granite and marble. Many buildings, sculptures, and other structures are made from one or both of these natural stone materials. Yet, these materials are not the same thing. In fact, each has specific advantages and disadvantages. In this article we will take a look at each of these materials. As we do, we will take note of the strengths of them. We will also consider the potential drawbacks of them. Thus giving you a simple granite vs. marble comparison.

Of What Are Granite and Marble Made?

First, let's specifically note that each natural stone will have a unique composition. So the components we mention here will only serve as a guide for what each of these materials contains. So, keep in mind the numbers will vary to some degree for a given stone.

Composition of Granite

According to one authoritative source, natural granite consists of feldspar, quartz, dark colored mainerals, sand, and mica. Keep in mind that science sources will define granite differently than a stone supplier might. So there will be some technical differences between geological granite and the granite countertop you install as a kitchen surface. Geologists can explain the differences accurately and there is information available online if clarification is needed. Note what geologist Karin Kirk says regarding this distinction in an article she wrote for usenaturalstone.org

In the natural stone industry, "granite" often means any hard stone that is not marble. Different dealers use the term granite slightly differently.

After establishing that not everything that is called "granite" in the commercial world is geological granite, she continues by scientifically defining granite in the following manner:

Geologist's granite is made of four minerals: feldspars, quartz, mica, and hornblende. The feldspars can be white, light grey, and/or pink. Quartz is usually glassy grey, the mica is black or silver flakes, and hornblende looks like black rectangles. Each of these ingredients is large enough to see and point to. The stone has a light color and a chunky texture that contains all of the colors evenly distributed throughout the stone, without any particular pattern or grain. Examples of geologist’s granite are Barcelona, Giallo Atlantico, White Mount Airy, and Luna Pearl.

So, granite materials will vary in composition based on what terminology is being used and whether a stone supplier is using the term granite to describe othe materials that are similar.

Composition of Marble

Like granite, marble also has distinctions that sometimes get masked by the labels put on the material. Note what the geologist mentioned above says in another usenaturalstone.org article describing marble and labeling:

The term "marble" is often applied broadly rather than literally. Many stone restoration professionals categorize marbles, limestones, and travertines together as a family of stone because they require similar maintenance and refinishing techniques. Polished limestone is sometimes called marble. While there's not a huge difference between the two, marble is much denser and therefore is resistant to staining. If a slab has fossils, shell fragments, or has open pockets within the stone, it is limestone.

Many stones classified as black marble are actually black limestones. This is particularly true for dark colored stones with stark white veins, like China Black, Dynasty Brown, or Nero Portoro.

Just as granite is a blanket term for several types of stone that are geologically different, so too marble is a term applied to a number of natural stone materials that are different by geological definition.

Composition Similarities and Differences

When it comes to composition granite and marble are different in the sense that each contains different minerals. Granite is composed largely of quartz, feldspar, mica, and horneblend (and as we have seen above, perhaps other minerals depending on how the supplier uses the term granite). On the other hand, marble is composed mainly of calcite. So, granite and marble are made up of different minerals from one another.

Granite and marble though are similar in terms of how each is actually used to represent other natural stone materials which are not geologically the same as the label being used.

Properties of Granite and Marble

The composition of natural stone affects the properties of that stone. So natural granite and natural marble have properties stemming from the minerals of which they are composed. Let's compare the properties of these two materials.

Similar Properties

Granite and marble are similar in that they are both natural stone materials. This means that each of these stones is porous to one degree or another. Porosity translates into a stone's ability to absorb liquids. The more porous a stone is, the easier it absorbs liquid.

Care and Maintenance

The porosity of a stone contributes to how a material must be cared for and maintained. For example, natural stone needs to be sealed if it is porous. Periodically applying an impregnating sealer helps with maintenance and cleaning. Sealed stone doesn't absorb liquid as quickly. As a result, spills can be cleaned up before water based and oil based liquids amke their way into the stone. Since both granite and marble are porous, sealing is beneficial for both materials.

Another way in which granite and marble are similar is that they require specific tools because of their degree of hardness. Granite is a hard stone and marble is a relatively soft stone. This means that each material has different cutting requirements.

Specialized Stone Tools

Specific diamond tooling is used for granite than is used for marble. Since each material has its own hardness (or softness, depending on how you look at it) different diamond tools are necessary. Hard stone like granite demands, for example, bridge saw blades for hard stone like granite while soft stone like calcareous stone require a marble bridge saw blades. We won't go into detail about the reasons why these materials require different blades. But essentially, it is because of each stone's hardness.

The last similarity we will discuss regarding these materials is the uniqueness in their color and appearance. Each natural stone offers this feature. Because of the way natural stone is formed, each slab (even ones cut from the same block) is 100% unique. This trait though can be amplified though.

Stone Enhancers & Color Treatments

Porous stone receives liquids very well. We mentioned that earlier in the article. That means liquid stone color enhancers can be used on any natural stone with pores! Both granite and marble are porous to one degree or another. Therefore, these color enhancing products wrok on these stones. In fact, some enhancers are also sealers too. Providing a double benefit.

In addition to enhancing the color of a stone, the color can be changed to a degree by applying another color treatment for stone. Stone dye for natural stone is made to change the color of natural stone materials. These products work on both grnaite and marble material.

Differing Properties

Just as granite and marble are similar in some ways, there are also some differences. One notable difference that we have already alluded to is the mineral content in each of these materials. As previously stated, granite consists of harder minerals than does marble. This translates into some specific differences between the two.

Scratch Resistance

The hardness of a stone contributes to its scratch resistance. In fact, the way a stone's hardness is measured is by using a scratch test to see how hard it is. Thus, one difference between marble and granite is the scratch resistance between these two materials.

Granite is more scratch resistant than marble. This is a direct result of granite being harder than marble. Before you deem granite to be a "better" option than marble though, consider how the material will be used. For example, sculpting with marble is easier because it is softer. Granite can be shaped too, just not as easily as marble.

Discolorations

Another difference between these materials is found in the ways they can discolor. We already said that both of these materials can be stained and that they needed sealer to help with this. However, granite and marble differ in that marble is susceptible to another form of discoloration. Namely, etching.

Etching is a term that refers to a discoloration that comes from a reaction in calcareous stone. Marble is a claceareous (composed of calcium carbonate) stone. Therefore, it can be "discolored" in this manner.

How Etches Happen

Etching in stone occurs when calcium carbonate reacts with acidic substances that come into contact with this mineral. Acid and calcium carbonate neutralize one another during the reaction. This means that the acid dissolves the calcium carbonate in the marble. When the calcium carbonate dissolves, it changes the appearance of the stone. Polished stone, will look dull and a honed surface will be slightly darkr in the spot where the etch occurs. There are products designed to repair or remove etching from marble, limestone, travertine, and onyx.

Since acids breakdown stone sealers and etch marble. The need for using the appropriate stone cleaner is heightened. Choosing a cleaner formulated for natural stone keeps the sealer in tact for as long as possible and reduces the frequency with which the stone needs to be treated.

As we have seen in this consideration of granite vs marble, it is not a question of whether one material is better or worse than the other. Rather, it is more about knowing the characteristics of each and selecting which material is right for your application. Getting to know how granite and marble are similar and how they are different allows the fabricator (and the consumer) to select the right product for the job.