What is Natural Stone?
Modern architecture calls for materials that are the merger of strength and aesthetics. Exterior applications such as flooring or wall paneling demand building materials that are strong enough to handle frequent usage and weather conditions. Interior applications such as kitchen/bathroom countertops and floor tiles require hard-wearing materials that are also visually appealing.
Natural stone has been the go-to material of choice for many years. In fact, entire structures have been built out of natural stone throughout our history spanning millennia.
This article takes an in-depth look at natural stone, its usage in modern architecture and construction, its various forms, and how you can source natural stone for building.
What is Natural Stone?
Natural stone is an organic formation extracted from the Earth’s surface through quarrying. There are several different types of natural stones. Most of these are very popular and used in residential and commercial construction projects.
Some popular natural stones include marble, granite, slate, limestone, quartz, sandstone, and onyx. The original stone pieces aren’t extracted from the Earth’s surface in the same stone condition seen in their final application. For instance, cutting quarried marble and polishing it is usually essential to make it usable for building purposes.
How are Natural Stones Made?
As the name hints, natural stone is made without any human intervention. Natural stone originates from one or more minerals compressed 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, resulting in rock formations in the Earth’s crust.
Large rock formations often break into smaller pieces due to erosion, high sub-surface pressure, and high temperature. These rock formations are used as quarries to extract the stone and turn it into products like stone tiles.
Classification of Natural Stone Formations
There are three different types of natural stone (rock) formations:
Igneous rocks form when the rocks below the surface undergo a rapid heating and cooling cycle. Magma inside the Earth cools and solidifies to form these rocks. These rocks are also created after the solidification of molten lava over the Earth’s crust. Examples of igneous rocks 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 planet’s surface. They are formed by a process known as sedimentation. Common examples of sedimentary rocks are limestone, sandstone, siltstone, and halite.
Metamorphic rock forms beneath the Earth’s surface as a result of igneous, sedimentary, or older metamorphic rocks being subjected to extreme heat and pressure. This heat and pressure change 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 numerous 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 softer, erode quickly, and are vulnerable to acid attacks. Let us study these varieties one by one:
Stone Resistant To Acid
Acid resistance is a desirable quality in a stone. It makes it usable for applications like 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 acid-resistant stone examples:
Granite is one of the most popular natural stones. It is an igneous rock composed of alkali feldspar, quartz, and plagioclase. Granite and marble have existed since ancient civilizations as far back as Ancient Egypt.
- Granite is considered very hard, tough, and abrasion-resistant, with a more compressed natural bedding plane than 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 or 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 cracks
- Flooring tiles
- Dimension stone
- Plane of reference (high polish granite)
- Cutting stones
Gneiss is an acid-resistant metamorphic rock. It is created when igneous and sedimentary rock is subjected to high pressure and temperature. Its visual appearance has bands alternating between light color and dark gray.
- Gneiss is incredibly hard, 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 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 schistosity. These rocks are typically composed of mica, talc, graphite, feldspar, chlorite, and quartz.
- High strength, except for the plane of weakness, where strength and adhesion are low.
- Average density: 2.73 to 3.19 g/cm3
- The compressive strength varies drastically based on the direction in which it is measured – usually from 20 to 40 MPa.
- Melting temperature: 650 to 700 °C
- Decorative rock walls
- Garden decoration
Quartzite is a metamorphic rock formed when heat and pressure are applied to quartz sandstone under the Earth’s surface. Quartzite is naturally dark gray in color. However, it often has an infusion of hematite resulting in various shades of red and pink colors. Other mineral infusions can also result in shades of yellow, green, and blue.
- Quartzite is very hard due to the interlocked quartz crystals inside it. It is harder than granite and has better stain resistance.
- 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 degree of heat and pressure it has undergone during its formation.
- Wall cladding
Sandstone is a sedimentary rock. It is 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 silicates). The presence of iron oxide in sandstone can give it a red appearance.
- Quartz sandstone is hard, thanks to the interlocking structure of quartz. Its 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 formation.
- Stone walls
- Foundation stone
- Decorative stone tiles
- Wall cladding
- Floors in chemical industries
Soapstone is a natural metamorphic stone very similar to schist. Soapstone is made from mineral talc with a high fraction of magnesium. Soapstone’s structure can be schistose (layered internal structure) or massive (without any internal structures).
- Soapstone is softer than 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 formation
- Wall tiles
Stone Non-Resistant to Acids
Stone non-resistant to acids is generally softer than acid-resistant stone tiles, with some exceptions. Non-acid-resistant stone is also vulnerable to weathering and erodes faster. Some examples are:
Limestone is a sedimentary stone. It is similar to sandstone but consists of calcites rather than silicates. Lime for industrial and construction use is extracted from limestone. The composition of limestone is mainly calcium carbonate in varying crystal forms. While one-fourth of all sedimentary stone is sandstone, limestone also has a similar fraction and abundance.
- Mohs 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
- Source of lime for manufacturing paper, steel, plastic, water purification, and many other industries
- Decorative Monuments
Marble is one of the most popular all-natural stones. It is a metamorphic rock made under the Earth’s surface by the transformation of limestone. It consists mainly of carbonate minerals such as dolomite or calcite.
- Mohs Hardness: 2 to 3. Marble is a relatively soft natural stone. It is often replaced by granite because of its more rugged properties.
- Density: 1.9 to 2.8 g/cm3
- Compressive Strength: 30 to 210 MPa
- Melting Point: 825 °C
- Marble is porous but impermeable.
- Table tops
- Interior decoration
- Luxury items
Onyx is a natural stone with band-like formations, a particular type of crystalline silicate. Onyx 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.
- Mohs Hardness: 7. While vulnerable to acids, onyx is relatively hard compared to the hardest acid-resistant rocks.
- Density: 1.1 g/cm3
- Compressive Strength: 100 MPa
- Onyx is permeable
- Fireplace surrounds
- 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.
- Mohs Hardness: 4 to 5. Travertine is softer than granite and other acid-resistant stones – but harder than soft stones like marble.
- 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?
Natural stone offers countless benefits for commercial or home interior applications. Some of these benefits include:
Natural stone has been present on the Earth’s surface for hundreds of thousands of years and was subjected to extreme temperature and pressure. Therefore, these stones are highly durable and can easily handle whatever you throw at them.
Natural stones do not require hard-to-do maintenance, unlike other materials such as wood or glass. The only maintenance required is to keep vulnerable stones like marble away from acids and abrasions. Stone, like granite, doesn’t need any maintenance, just time-to-time cleaning.
When using natural stone for your interior or exterior applications, there is a wider range of options than any other building material. Even if you decide on a 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 essential to factor in that natural stone lasts many times longer and doesn’t get damaged.
Natural stone is one of the most environmentally friendly materials out there. This is true for the material itself and the processing of natural stone. On the other hand, materials like wood or concrete are highly toxic to the environment in the extraction and 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.
Natural stone with a honed finish first undergoes grinding and then sanding. This process creates a matte surface on the natural stone. It feels soft to the touch and looks elegant without reflecting too much 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 surface of the tumble-finished stone is very soft. The tumbling process 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 are easy to repaint to change their natural color. Even without repainting, natural stones have an almost unlimited variety of colors and are available in many possible options.
Some typical colors are gray tones, red, blue, green, beige, black, and white.
What is 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 varies significantly based on the type of tile and the dimension. The general thickness of a 12-inch natural stone tile is 3/8 inches.
- The thickness of 16 to 24-inch square tiles varies from 0.5 to 0.75 inches. For applications like kitchen countertops, thicker slabs are preferred.
- For rectangular slabs, the size varies from 104 x 70 inches to 125 x 80 inches.
Tips For Selecting a Natural Stone
When choosing which natural stone you require, follow the tips below:
- It is best to choose a stone that is acid resistant and does not erode quickly for exterior applications such as wall cladding or patio flooring. This is because of the harsh weathering conditions that the stone will endure.
- Applications such as kitchen countertops also require an acid-resistant stone to prevent damage 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 wise 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 to fit specific spaces. But smaller stone tiles cannot be made larger.
- 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. It is better to go with a reputed supplier for the best quality and value for money.
Leading Supplier of Natural Stone Tiles
Premier Precast provides premium quality natural stone products in various 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.
You can never go wrong with natural stone when deciding between different types of building materials. After reading all the information presented in this article, you are now well-versed in what natural stone is 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 the most durable stones. Granite is considered the leading choice over other stones as it is highly durable with a superior visual appearance and abrasion resistance.
Is natural stone easy to maintain?
Yes, natural stone is the easiest material to maintain. You only 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 water does not damage them.
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 because 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 stones and their visual appearance and environmental friendliness make them a more cost-effective and preferred option.