Sandstone and Quartzite are two stones that are often confused.
To help you be able to identify them more easily, here is what you need to know about these two different types of rocks.
Sandstone vs Quartzite: The Facts
What Is Sandstone?
Sandstone is a sedimentary rock that is created from tiny sand-sized bits of rock, mineral, and organic material.
These grains are cemented together by silica, calcium carbonate, or iron oxide that act to keep the grains together.
Depending on the composition of these materials, sandstone can take on a wide variety of colors.
These can include grey, white, brown, red, pink, or even nearly black.
It’s worth noting that the ‘sand‘ in sandstone, doesn’t refer to its composing material, rather it refers to the size of the grains that comprise it.
These particles can range in size from 1/16 millimeters to 2 millimeters in diameter.
These grains usually come from minerals, rocks, or bits of organic matter that have been reduced to a sand grain size via weathering.
Sandstone can be rated as a seven on the Mohs Hardness Scale.
However, this is due largely to the individual quartz grains that comprise it.
If it hasn’t cemented well or has been cemented by calcite, for instance, it can be quite easy to break, making it seem softer.
Sandstone is one of the most common sedimentary stones and it is found in great quantities across the globe. It is formed when sand-sized particles are laid and buried.
This often happens due to river deltas, although beaches and dunes can create sandstone as well.
For instance, the sandstone cliffs of the Grand Canyon were formed out of a desert setting and worn down via weathering.
How Is Sandstone Used?
Sandstone has been used since prehistoric times and has persisted as a popular building material due to how easy it is to carve and manipulate.
Depending on the composition, some sandstone can be quite resistant to weathering, making it a good choice for paving material.
Sandstone has also often been used as a grindstone material due to the individual grains and the relative uniformity of its structure.
This makes it good as a tool for sharpening blades or other tools.
What is Quartzite?
While sandstone is a sedimentary rock, quartzite is a metamorphic rock that is comprised almost entirely of quartz.
Quartzite actually forms from quartz-rich sandstone that is altered under intense pressure and heat deep in the earth.
When the sandstone is subjected to these conditions, metamorphism occurs, recrystallizing the quartz grains and the silica that binds them.
This transforms and fuses them together, resulting in an extremely strong bond.
One defining characteristic that differentiates quartzite from sandstone is the interlocking crystal structure that makes it so strong and durable.
Because of this hardening, quartzite is rated at a seven on the Mohs Hardness Scale.
While this is relatively the same as sandstone, due to the fusion of quartz and silica, it is often much harder to break, making it seem stronger than sandstone overall.
Quartzite is most commonly formed during mountain-building and in places around convergent plate boundaries.
These places allow for the correct amount of heat and pressure to be applied to induce metamorphism.
Because quartzite is so resilient, it is often found along the crests of mountain ranges after other less-durable rocks are worn down and destroyed by erosion and weathering.
How is Quartzite Used?
Like sandstone, quartzite is often used as a building material. Crafted into bricks or crushed into gravel, it is versatile for both indoor and outdoor use.
Because it is so hard, quartzite is often not quarried below ground and tends to be taken from above-ground deposits.
Today, quartzite is most commonly used for flooring, fireplaces, countertops, and vanities.
The Term ‘Quartzite’
It’s also worth mentioning that the term ‘quartzite’ has been used differently by various geologists.
Some sedimentary rocks with a high quartz content, now called quartz arenite, have previously been referred to as quartzite.
While this has fallen out of favor in recent decades, some older books may still use this terminology and it’s worth keeping an eye out for.
It should also be noted that some sedimentary structures, such as the Tuscarora Sandstone in the Appalachian mountains, can, in some respects, fit the description of quartzite in parts of it that have metamorphosized.
However, other parts of it are better described as sandstone. Because of situations like this, inconsistency in the way the term quartzite is used can be more common than not.
Why Are These Rocks Commonly Confused?
Sandstone and quartzite can be commonly confused as their appearances can be quite similar.
Both can be found in similar colors, such as orange, white, grey, brown, and pink.
Similarly, since they both have a hardness of seven and can scratch glass — due to the quartz content of each — and neither will be affected by common acids, it can be particularly difficult to determine which is which.
How Can You Tell Them Apart?
In order to tell these two stones apart, look at them closely to see if you can identify individual grains.
If you cannot, and the surface appears crystallized, you’re probably looking at quartzite.
The biggest difference between these two stones will be the way they fracture, and it is one of the best ways to tell them apart.
If you use a rock hammer to break sandstone, the sandstone will fracture around the quartz grains so that they are individually visible.
Quartzite will break through the quartz grains so that you will not be able to see the individual unfractured grains.
However, when using a rock hammer on quartzite, or what you think may be quartzite, use caution.
Always wrap the rock before hitting it, and wear protective gear as shards can break off and cause injury.
Additionally, trying to sharply hit it with a hammer can result in a bounce-back, that can send the hammer back at you.
Similarly, if examined under a microscope, quartzite will exhibit a tight interlocking network of crystal structures that isn’t present in sandstone.
Metaphysical Properties of Sandstone and Quartzite
Throughout history, stones have been assigned special properties that attribute metaphysical aspects to them. Sandstone and quartzite are not different.
Today, many people associate sandstone with creativity and clear thoughts.
Some people believe that having sandstone in your workspace can help boost your efficiency by allowing you to more easily form creative ideas without being bogged down by other thoughts.
Quartzite is said to be good for promoting positive energy and preventing negative emotions from permeating your mind.
Many people believe quartzite is particularly special since it combines all of the elements. Earth, as a compositing material, wind and water as a weathering agent during its time as sandstone, and fire as the heat that changed it to quartzite.
While there is no scientific basis for these beliefs, they are worth noting since the history of these ideas is long.
Two Similar, But Different Rocks
Sandstone and Quartzite can be extremely similar and yet incredibly different.
While the terms have often been used inconsistently in some aspects of geology, it is important to note their unique properties and how you can most easily tell them apart.