Does "Hard Marble" Exist?
It's a question that some may contemplate. "Does hard marble actually exist?" The reasons for the question comes from a basic difference in the way natural stone is perceived by the ones considering materials given the name. In this article, we will endeavor to clarify the answer to that question.
Why Consider Whether Marble Is a Hard Stone?
Marble is a well-known material used for a variety of purposes. Everything from buildings to sculptures are made from natural marble. It is a prominent material that many consumers have heard of. So, why consider whether hard marble exists? In other words, why do some hear about "hard marble" when they are looking for a countertop surface? You may be wondering whether this actually happens. There are examples such as
this one that demonstrates how easy it is to find someone asking questions about "hard marble".
Why the Question?
The question of why people wonder if hard marble exists can be answered by looking at the uses of the term. There are multiple uses of the name marble as it relates to stone. One way the name is used is in the context of the commercial stone industry. The other is in the geological sense. The commercial stone use of the name focuses more on the practical use and how the stone looks. On the other hand, the scientific name "marble" is based on the properties of the material; among other things. As a result, there may be variations in how the term is applied depending on the context in which it is used.
Properties That Define Geologic Marble
Geologically speaking, marble fits a specific set of criteria. A couple of the characteristics that define marble in the geological context include its composition and how it forms. There are other requirements but our goal here is simply to acknowledge the reason why the vague names exist and not to explain the scientific definition.
Marble is, in simple terms, a natural metamorphic rock that consists primarily of calcium carbonate. There are other rock types that do not scientifically fit the definition of marble, but are called such.
Why Are Some Stones Called Hard Marbles?
Simply put, some stone is labeled as marble even though it is not because of the color and location. Other stone is marble but manifests characteristics out of the norm because of how the material's composition.
Natural Stone Institute cites the U.S. Geological Survey in its explanation of the reasons why names "overlap" and then that reference goes on to say:
Historically, it has been commercial practice to group stones within performance and behavioral groups as opposed to true scientific definition.
By grouping stone based on the performance and behavioral characteristics, consumers are able to better understand what they are buying from a practical perspective. But just know that in a scientific sense a stone that is called marble could be a different stone altogether with a label of marble on it. Let's look at some examples.
An example of a stone receiving an incorrect label is "green marble". There is marble that is green. However, there is also a completely different stone referred to as
serpentine that is green. Serpentine though, is not marble and has a different composition. Serpentine can be composed of various minerals that range in hardness. So the hardness of serpentine can be anywhere from 3 to 6 on the Mohs scale. Since marble is on the softer end of this scale, it is easy to imagine a case where a "soft serpentine" might get labeled as green marble because of the similar "performance and behavioral" traits. Keep in mind though, that serpentine minerals can actually be harder than traditional marble. But is there a circumstance where a "marble" can actually be harder than normal marble?
Extraordinary Marble? Or, Misnomer?
We have already looked at a situation where a stone can be called marble because of its practical use potential. But is the inverse possible? Can a stone that qualifies as marble actually be harder than normal? To answer that we first must cite reference above (Natural Stone Institute) again.
While scientifically there are hundreds of rock type identifications, only nine groups are commonly acknowledged commercially: Granite, Limestone, Marble, Onyx, Quartzite, Sandstone, Serpentine, Slate, Soapstone, and Travertine. This means that some rocks are included in groups which are not perfectly coincident with their scientific definition.
On the surface that list looks like a list of ten stones, but the document specifically says there are only nine. Perhaps this is because that last one listed (
travertine) and the fourth one list (onyx) are two variations of the same stone. But you get the idea. The scientific identifications far outnumber nine or even ten groups. Therefore, there are going to be cases where a stone is behaviorally one of the ten listed above, but technically it is, scientifically speaking, actually a different stone.
Quartzite, a Marble Look-a-like
One situation where a stone of one type can be mistaken for a stone of another type is in the case of a marble with pockets of quartz or a marble slab labeled "soft quartzite". As we stated previously, stone varies in its composition. Calcite (the primary mineral in marble) and quartz (virtually the only mineral in quartzite)look alike. So imagine being in a situation where there is a slab that is has a large amount of quartz in it, but it looks like marble and in fact is primarily (more than 50%) made up of calcite. Calling it a "soft quartzite" could cause confusion. However, could it truly be called a "hard marble"?
So, Do hard marbles exists? it all depends on the context (scientific or commercially speaking), the factors (the composition of the stone), and how the material is presented. Being aware that the name of the stone is not as important as understanding its properties is the key. If you can identify the properties of the stone and translate those into use cases, you will be better equipped to not only identify slabs, but also choose them wisely and communicate the benefits to others.