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Sandstone & Quartzite

Comparing Quartzite With Sandstone

You may not think about it a lot. But there are technical differences between natural stone materials. Even stone that is composed of the same minerals is classified into differing groups. For example, limestone and travertine are largely made up of the same main mineral. And technically, travertine is a specific type of limestone. However, they are described by science as different natural stones. And while some natural stone comparisons will differ greatly (for example, Comparing Marble and Granite), others will be very similar even though they are different materials. In this article we will take a look at such a comparison as we consider quartzite vs. sandstone. As you will see, comparing quartzite with sandstone will contrast only when we get down to the nitty gritty details of the subject.

The Purpose of the Comparison

One of the first questions that may come to mind is, "Why compare quartzite wih sandstone?" The answer to that question in this case is to highlight the details that distinguish on material from the other. Additionally, comparing these natural stones will demonstrate why sandstone slabs are sometimes marked and sold as quartzite slabs even though scientifically they are different stones.

What is Sandstone?

It is not likely to surprise you to find out that sandstone is made of, well, sand. It is right in the name; sandstone. But what makes it a stone and not just sand? In other words, how does sand come to be rock? We won't delve into the scientific details of this here, but if you are interested, you can read all about it in Sussing Out Sandstone; an article written by a geologist that details the process. But to put it simply, sand becomes stone when some mineral makes its way into the spaces between grains of sand and "glues" them together. The result is sandstone. So sandstone is just sand particles glued together by mineral deposits.

How Quartzite Forms

Quartzite is composed of the same material that sandstone is except quartzite is structurally different from sandstone. So does quartzite form? Well, quartzite forms when sandstone is "pressed" into a new type of stone. We use the term "pressed" because the actual process involves heat and pressure. When sandstone is exposed to intense heat and pressure from natural forces, the grains of sand are fused together to create a solid mass of material. This material is quartzite. So, to put it in simple terms, quartzite is a stone that used to be sandstone before it was compressed by extreme forces.

Composition of Sandstone and Quartzite

As we already mentioned, sandstone and quartzite have the same composition (this makes sense since one is formed directly from the other). But what is in these materials? Here is a list of some of the substances that are found in both sandstone and quartzite slabs:

  • Quartz
  • Feldspar
  • Mica
  • Clay
  • Iron Oxide
  • Silica
  • Calcite

Of course not all sandstone and quartzite will have the same amounts of these minerals, but these are some of the substances that make up thse natural stones.

Similarities Between Quartzite & Sandstone

Depending on various factors, sandstone and quartzite can be more or less similar in their properties. Sandstone that has a lot of quartz in it for example, will be very hard, but depending on the mineral(s) that glue(s) the particles together, it may be easier to cut and/or shape than a quartzite with many of the same minerals.

Because the process that transforms sandstone into quartzite takes a long time, there are many variations of rock that are somewhere between sandstone and quartzite. This makes the distinction between these materials somewhat challenging for someone that is not an expert.

How to Tell the Difference

A simple rule for determining whether a slab is quartzite as opposed to sandstone is to look very closely at the stone. Quartzite will not have visible grains of material. Sandstone will have sand grains that you can see. Remember, quartzite is sandstone that has the grains fused together. This means the individual grains are transformed into a different material.

Sandstone will have varying degrees of porosity, where quartzite will have low porosity. And some sandstones (depending on the amount of heat and pressure to which they have been exposed) will have low porosity. The best way to check the porosity of a slab is to perform an absorbancy test on the slab. Absorbancy is checked by simply pouring water on the stone and observing whether the stone absorbs the water. The faster the water is absorbed, the more absorbant it is.

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