Modern architecture calls for materials that are the merger of strength and aesthetics. When it comes to exterior applications such as flooring, paneling, or countertops, the material should be strong to handle the usage conditions and visually appealing to improve the interiors.
Natural stone has been the material of choice in this regard for many years. In fact, entire structures have been built out of natural stone throughout a history spanning millennia.
In this article, we will have an in-depth discussion on what is natural stone, its usage in modern architecture and construction, various forms of natural stone, how you can source it, and many other things.
What is Natural Stone?
Natural stone is an organic formation extracted from the earth’s surface through a process called Quarrying. There are several different types of natural stones, most of them very popular and used commonly in residential and commercial constructions.
Some of the popular natural stones include marble, granite, slate, limestone, quartz, sandstone, onyx, and more. These stones aren’t extracted from the earth’s surface in the same condition that you see in their application. For instance, quarried marble goes through a lot of processes such as cutting and polishing to make them usable for any purpose.
How are Natural Stones Made?
As the name hints, natural stone is made by nature itself, without any human intervention. Stones present inside the earth formed in its crust thousands or even millions of years ago. After its origin, the earth was full of gases with mineral compositions. Over time, these gases solidified and resulted in rock formations in the earth’s crust.
Large rock formations often break into smaller pieces of stones due to factors such as erosion, high pressure under the surface, and high temperature. These rock formations are used as quarries to extract the stone and turn them into respective stone tiles.
Classification of Natural Stone Formations
There are three different types of natural stone (rock) formations:
Igneous rocks form when the rocks inside the earth’s surface go through rapid heating and cooling cycle. Magma present inside the earth’s surface cools and solidifies to form these rocks. These rocks are also created after the solidification of molten lava over the earth’s crust. Common examples of igneous rock are granite, basalt, diorite, and mica.
Sedimentary rocks are formed when mineral compositions collect over one place and solidify with time. These rocks are usually present under water bodies or deposited on the surface of the earth. These rocks are called sedimentary because they are formed with the process of sedimentation.
Common examples of sedimentary rocks are limestone, sandstone, siltstone, and halite.
Metamorphic rocks are formed when igneous, sedimentary, or older metamorphic rocks under the earth’s surface are transformed by heat and pressure. The application of heat and pressure changes the physical properties and appearance of the original rock.
Common examples of metamorphic rocks are marble, slate, and quartzite.
Different Varieties of Natural Stone
Natural stones exist in many different varieties, each with its own texture, color, hardness, and chemical composition. Some of these varieties are hard, rugged, acid resistant, and slow to erosion. Other varieties are relatively softer, erode quickly, and are vulnerable to acid attacks. Let us study these varieties one by one:
Stones Resistant To Acid
Acid resistance is a great quality in a stone, as it makes it usable for applications such as kitchen countertops and outdoor usage. Acid resistance usually comes hand in hand with extra ruggedness, making these natural stone tiles last longer. Here are some of the acid-resistant stones:
Granite is one of the most popular natural stones. It is an igneous rock, composed of alkali feldspar, quartz, and plagioclase. Granite, along with marble, is an industry that has been present since ancient civilizations as far back as Ancient Egypt.
- Granite is considered very hard, tough, and abrasion-resistant when compared to other natural stones like marble. Visually, granite has a coarse-grained appearance.
- Average density: 2.65 to 2.75 g/cm3
- Compressive Strength: 200 MPa and more
- Melting temperature: 1215 to 1260 °C at ambient pressure
- Poor primary permeability (ability to allow the water to pass through pores)
- Strong secondary permeability in the presence of cracks
- Flooring tiles
- Dimension stone
- Plane of reference (high polish granite)
- Cutting stones
Gneiss is an acid-resistant metamorphic rock, created due to the application of high pressure and high temperature on igneous rock and sedimentary rock. Its visual appearance has bands alternating between light color and dark gray.
- Gneiss has a high hardness, significantly more than granite.
- Average density: 2.6 to 2.9 g/cm3
- Compressive Strength: 152 to 248 MPa
- Melting Temperature: Partial melting occurs at around 950 °C.
- Gneiss has a very low permeability
- Construction aggregate for asphalt pavements
- Ornamental stone tiles
- Facing stones
Schist is a type of metamorphic rock with medium grains. The rock has parallel plates of mineral grains, giving it the visual appearance termed as schistosity. These rocks are usually composed of mica, talc, graphite, feldspar, chlorite, and quartz.
Schist rocks have high strength, except for the plane of weakness where the strength and adhesion is very low.
Average density: 2.73 to 3.19 g/cm3
The compressive strength varies drastically based on the direction in which it is measured. It usually varies from 20 to 40 MPa.
Melting temperatures: 650 to 700 °C
- Decorative rock walls
- Garden decoration
Quartzite is a metamorphic rock formed when heat and pressure applies on quartz sandstone under the earth’s surface. Quartzite is naturally dark grey in color. However, it often has an infusion of hematite resulting in various shades of red and pink colors. Infusion with some other minerals can also result in shades of yellow, green, and blue.
- Quartzite has very high hardness due to the presence of interlocked quartz crystals inside it. It has higher hardness and stain resistance than granite.
- Average Density: 2.6 to 2.8 g/cm3
- Compressive Strength: Around 300 MPa
- Melting Temperature: 1350 to 1500 °C
- Quartzite can be permeable or non-permeable, depending on the amount of heat and pressure it has undergone during its formation.
- Wall cladding
Sandstone is a sedimentary rock made of grains of silicate about the size of sand and iron oxide. Sandstone is the most abundant of all sedimentary stones, making up for one-fourth of these rocks. Sandstone is usually composed of feldspar or quartz, both of which are silicates. Presence of iron oxide in sandstone can give it a red appearance.
- Quartz sandstone has a high hardness due to the interlocking structure of quartz. The hardness can vary significantly based on the mineral compositions of sandstone.
- Density: 2 to 2.6 g/cm3
- Compressive Strength: 14 to 60 MPa
- Melting Temperature: 1500 °C
- Sandstones have a high permeability due to their highly porous nature.
- Stone walls
- Foundation stone
- Decorative stone tiles
- Wall cladding
- Floors in chemical industries
Soapstone is a metamorphic natural stone very similar to the schist. Soapstone is made of mineral talc with high fraction of magnesium. The structure of soapstone can be schistose (layered internal structure) or massive (without any internal structures).
- Soapstone has low relative hardness compared to granite and other natural stones due to the high amount of talc.
- Density: 3g/cm3
- Compressive Strength: 60 to 100 MPa
- Melting Temperature: 1600 °C
- Soapstone is non-permeable due to its non-porous and hydrophobic nature
- Wall tiles
Stones Non-Resistant to Acids
Stones non-resistant to acids are generally softer than acid-resistant stone tiles, with some exceptions. Acid non-resistant stones are also vulnerable to weathering and erode faster. Some of these stones are:
Limestone is a sedimentary stone similar to sandstone, but made up of calcites instead of silicates. Lime for industrial and construction uses is extracted from limestone. Main composition of limestone is calcium carbonate in varying crystal forms. While one-fourth of all sedimentary stone is sandstone, limestone also has a similar fraction and abundance.
- Mohr’s Hardness: 2 to 4. Limestone is harder than soapstone but relatively softer than most other natural stones.
- Density: 2.71 g/cm3
- Compressive Strength: 180 MPa
- Melting Temperature: 825 °C
- Limestone is permeable in nature
- Source of lime for manufacturing paper, steel, plastic, water purification, and many other industries
- Decorative Monuments
Marble is one of the most popular choices among all natural stones. Marble is a type of metamorphic rock, made of mainly mineral carbonate minerals. Common constituents include mineral dolomite or calcite. Marble is commonly made under the earth by the transformation of limestone.
- Mohr’s Hardness: 2 to 3. Marble is a relatively soft natural stone, and is often replaced with granite in high hardness and rugged requirements.
- Density: 1.9 to 2.8 g/cm3
- Compressive Strength: 30 to 210 MPa
- Melting Point: 825 °C
- Marble has a porous nature, but it is impermeable.
- Table tops
- Interior decoration
- Luxury items
Onyx is a natural stone with band-like formations, a particular type of crystalline silicates. The stone and the bands can be of any color, but black and white bands are most commonly found. Onyx is sometimes wrongly associated or labeled with banded varieties of marble and other natural stones.
- Mohr’s hardness: 7. While vulnerable to acids, onyx has a high relative hardness, comparable to the hardest acid-resistant rocks out there.
- Density: 1.1 g/cm3
- Compressive Strength: 100 MPa
- Onyx is permeable in nature
- Fireplace surround
- Decorative items
- Bar tops
Travertine is a popular variety of natural limestone. Unlike natural limestone, travertine limestone is found in terrestrial formations near water springs. Travertine limestone comes in shades of white and gray. It is formed by the deposition of calcium carbonate due to water springs.
- Mohr’s hardness: 4 to 5. Travertine is relatively softer than granite and other acid-resistant stones, but relatively harder than other soft stones like marbles.
- Density: 2.5 g/cm3
- Compressive Strength: 42.3 MPa
- Travertine is porous and permeable in nature.
- Pool decks
What are the Advantages of Natural Stone?
There are countless benefits of using natural stone in your commercial or home interior applications. Some of these benefits include:
Natural stone has been present in the earth’s surface for hundreds of thousands of years and endured extreme temperatures and pressures. Therefore, these stones are highly durable and can easily handle whatever you throw at them.
Natural stones do not require any hard-to-do maintenance than other materials like wood or glass require. The only maintenance required is to keep vulnerable stones like marble away from acids and abrasions. Other stones like granite don’t require any amount of maintenance at all, just time-to-time cleaning.
When using natural stone for your interiors or exterior applications, there is a wider range of options than any other material. Even if you decide on any particular natural stone, there are countless colors, sizes, qualities, and designs to choose from.
Due to their long lifespan and no maintenance costs, natural stones are a very cost-effective solution. The initial cost of any natural stone can seem to be higher than other alternatives, but it is important to factor in that natural stones last many times longer and do not get damaged.
Natural stone is one of the most environmentally friendly materials out there. This is true not just for the material itself but also for the processing of natural stone materials. On the other hand, materials like wood or concrete are highly toxic to the environment in the extraction as well as processing stages.
What are the Most Common Stone Finishes?
Natural stone tiles are available in many finish options for stone surfaces. The three most commonly used options are:
Polished stone surfaces are obtained by rubbing the natural stone tiles with a grinding stone and buffing it repeatedly. These stone surfaces are very glossy, smooth, and reflective in nature. In this finish, one can see the natural patterns and the inherent visual appearance of the stone.
For a honed finish, the natural stone first undergoes grinding and then sanding. This process creates a matte surface on the natural stone. It feels soft to the touch and elegant, without reflecting too much of the light. This natural stone finish is slip resistant.
Tumbling is a process that adds an aged visual look with natural quarry texture to the stone, making it look antique and sleek. In this process, the natural stone is put in a drum along with sand and water. The drum is then tumbled to let the sand work on the stone surfaces. The stones with tumbled finish have a very soft surface. Tumbling is a long process and can take three to five weeks.
What are Color Options in Stone?
The color choices in natural stone mainly vary based on the type of natural stone you choose. Some stones such as onyx can also be repainted with ease, making the paint appear as its natural color. Even without repainting, natural stones have an endless variety of colors and are available in almost all possible options.
Some of the common colors are shades of gray, red, blue, green, beige, black, and white.
What are the Most Popular Stone Size and Thickness?
Natural stone is available commercially as a large precut natural stone tile of standard sizes. Buyers purchase these tiles based on requirements and cut them further based on applications.
- Natural stone tiles are usually available in square cut shapes with side dimensions of 4 inches, 6 inches, 8 inches, 12 inches, 16 inches, 18 inches, and 24 inches.
- The thickness of stone tiles can vary significantly based on the type of tile and the dimension. The general thickness of a 12-inch natural stone tile is 3/8 inches.
- For 16 to 24-inch square tiles, the thickness can vary from 0.5 inches to 0.75 inches. For applications like kitchen countertops, thicker slabs are preferred.
- For rectangular slabs, the sizes can vary from 104 x 70 inches to 125 x 80 inches.
Tips For Selecting a Natural Stone
For choosing which natural stone you require, follow the tips below:
- When choosing natural stone for any exterior applications such as wall cladding or patio flooring, it is important to choose a stone that is acid resistant and does not erode quickly. This is because of the harsh weathering conditions that the stone will endure.
- Applications such as Kitchen countertops also require an acid-resistant stone so that it is not damaged by food oils and substances like vinegar. This is why granite is the preferred kitchen countertop material instead of marble.
- While purchasing a natural stone tile, it is important to go over the required size than under it. This is because the stone tiles are often cut during application to match the dimensions of the requirement. Large tiles can be cut for matching smaller requirements, but smaller stone tiles cannot be installed into larger dimensions.
- The finish and quality of any particular natural stone can vary drastically between suppliers. You might find a cheaper option in a local store, but it will also come with significant compromises in quality. For the best quality and value for money, it is better to go with a reputed supplier.
Leading Supplier of Natural Stone Tiles
Premier Precast provides premium quality natural stone products in a variety of sizes, thicknesses, and finish options. All products & tiles are procured from the best quarries globally. This is why Premier Precast is the first choice of knowledgeable builders throughout the country for various types of building materials.
There is also expert assistance available for any installation queries.
When deciding between different types of building materials, you can never go wrong with natural stone. After reading all the information presented in this article, you are now well versed in what is natural stone and how to procure it.
Frequently Asked Questions
Here are the answers to common questions regarding natural stone:
Is natural stone durable?
Yes, natural stone is highly durable and can last for ages. This is one of the main reasons that builders prefer it over other alternative building materials.
Which natural stone is most durable?
All acid-resistant natural stones are winners when it comes to most durable stones. Granite is considered the leading choice in this regard over other stones, being highly durable along with the exceptional visual appearance and abrasion resistance.
Is natural stone easy to maintain?
Yes, natural stone is the easiest material to maintain. You just have to clean it occasionally and keep it away from acids that can harm it (only in the case of marbles and acid-vulnerable stones).
Is natural stone waterproof?
Yes, natural stones are waterproof in nature. Some natural stones like sandstone are permeable but still they do not get damaged by water.
Does natural stone fade?
Fading is observed in very few natural stones. In case of fading, the original shine of the veneer stone can be restored by polishing it again.
Is natural stone more sustainable than concrete?
Yes, natural stone is considerably more sustainable than concrete. This is because, unlike concrete, natural stone is not toxic and does not cause any water wastage in processing.
Is natural stone expensive?
Natural stone can be more expensive than materials like concrete. However, the long lifespan of natural stone along with their visual appearance and environmental friendliness make them a more cost-effective and preferred option than concrete.