Onyx vs Sandstone

One material is a sedimentary stone that forms from a very common particulate and the other is a metamorphic rock with traits that make you take note. Each is a natural material that has gained a measure of interest and yet, these materials are very different from one another. That is not to say that they have nothing in common though. In our match up today of onyx vs sandstone we will take a look these intriguing materials. As we do, we will mention some of their properties, and we will compare them.

"Onyx"ly Speaking

An honest look at what is sometimes called "natural onyx" requires short explanation. In the commercial stone industry, terms are not used in the same way as they are in the world of science. This is one example of that fact. Geologists use the scientific classifications for stone whereas the commercial world identifies materials from a practical standpoint. As a result, the material that we are calling "onyx" in this article is what geologists call "banded calcite". Additionally, science applies the name "onyx" to a specific mineral that is not calcite at all. Thus, in this article when we use the term onyx we are speaking in the commercial stone industry sense of the word and not in the scientific sense.

What is Onyx?

Onyx is a form of calcareous stone that is closely related to other stone containing calcite. Some of these are marble, travertine, and limestone. Like those materials, onyx is primarily composed of calcium carbonate (also called calcite). In fact, you can even say that onyx is the same stone as travertine, just in a different variation. Note the following comment from Karin Kirk, a geologist in one of her natural stone articles:

Onyx and travertine are variations of the same stone. They come about from mineral-laden water, like you’d find at the mouth of a hot spring. Both are made of calcite, the same mineral that’s in limestone and marble.

Now that we have taken a brief look at the first contender in our "versus" match-up, onyx, let's look in the other corner.

The "Partic"ulars of Sandstone

In contrast with onyx, natural sandstone is simple to explain. It is a rock that forms from... wait for it... correct! Sand! Silica sand particles make up the large part of this material and these are cemented together by other materials to form sandstone. That is about all for the summary of sandstone. I told you it is simpler to explain.

Comparing Onyx and Sandstone

We have finally come to the part of the discussion where we compare these two interesting materials. But before we begin looking at the similarities and differences, it is good to establish briefly why it matters. Consumers are interested in comparing stone materials because it helps them make buying decisions. Knowing how a given material will hold up to normal wear and tear in certain environments helps with making the decision.

Porosity Comparison

When it comes to porosity, the general truth is this: virtually all stone is porous to a certain degree. Natural stone is porous by nature. As a result, materials like onyx and sandstone are treated using a sealer designed for natural stone. These impregnating sealers work to keep oil and water based liquids on the surface of the stone so that they don't get into the pores and create stains.

Another basic truth is that every stone varies in its porosity. In other words, two stones of the same type may differ somewhat in their porosity because of forming in different areas. In fact, even different parts of the same stone might have variations in porosity. That means, each of our contenders, onyx and sandstone, benefit from being sealed using the appropriate sealer.

Hardness Compared

When looking at onyx vs sandstone another aspect of the comparison is the hardness of each stone. In the case of the two materials we are considering, this is a difference. Onyx, being calcareous is relatively soft compared with sandstone. Natural stone hardness is usually measured using the Mohs scale of mineral hardness. The scale ranges from 1 to 10 with 1 being the softest and 10 being the hardest. So, where do onyx and sandstone fall on that scale?

Hardness of Onyx vs Sandstone

On the Mohs scale, the onyx we are talking about here resides at 3. Sandstone, on the other hand, ranges anywhere from 6 to 7. As you can see then, onyx is a delicate stone compared with sandstone. Does that mean then that sandstone is better? That depends on what you are using the material for and what the environment will be. For example, think about how each of these materials would fare as a fireplace surround. This type of use does not require an extremely hard stone. Now think of a case where sculpting is going to be done, the harder the stone, the more difficult it will be to sculpt. You get the idea, harder is not always better in every case.

Blades for Cutting Onyx & Sandstone

Another facet of the hardness of these two materials is the blades used to cut them. Sandstone, being on the harder end of the scale requires a different kind of diamond blade than the onyx does at the low end. That's why you see a variety of diamond blades when shopping for blades. Take for example, marble bridge saw blades, hard stone bridge saw blades, and various blades for calcareous stone.

The blades for hard stone may cut the softer stone well, but the opposite might not work as well. In fact, there are some cases where using a blade specifically designed for cutting marble is preferred. The point? Choose the blade that is made to do what you are working on. Having the right tool makes the job much smoother in more ways than one.

Comparing Appearance

Here is where our discussion of onyx vs sandstone gets interesting. Each of these materials has very appealing visual traits. The color selection, and other intricacies of the stone's look make each of these materials great options for interesting designs and focal points.

Sandstone's Visual Appearance

Sandstone forms in all the colors in which you find sand. White, cream, beige, red, etc. And that makes sense, doesn't it? Since the stone is formed from sand, it stands to reason that you would see all the same colors of sandstone as the sand you see.

Shining Light On (and Through) Onyx

As is the case with sandstone, onyx too is a visually diverse material. It comes in various colors, but the most common is a honey gold color. However, there is another captivating trait that onyx offers; one that makes it stand out in a crowd of other natural materials. Parts of onyx slabs are translucent and allow light to pass through the slab. Because of this characteristic, you often see onyx used, not as a counter top surface, but as a surface used for a focal point. For example, the front face of a bar that has a different material used for the top. LED lighting is often installed behind the surface so the onyx is backlit to highlight the stone's texture.

Which is Better, Onyx or Sandstone?

Asking whether onyx or sandstone is better is like asking if a chair is better than a table. Each one has a horizontal plane and each one has legs. In fact, both chairs and tables are furniture. Yet, the best results come from using the one that is the best fit for the task at hand. You can set on a table, and you can place a prepared meal on a chair. But is it the best way to do it? Likewise, the characteristics of onyx and sandstone lend themselves to various applications and knowing the strengths of each material allows you to use each one in the best way possible.

In conclusion, our consideration of onyx vs sandstone shows that each material brings benefits to specific situations. Both onyx and sandstone have positive aspects that make each of them a great option in a number of cases. So