When selecting elements for your home, there is one thing you need to consider, and that is durability. I want to know that my finishing material will last for decades and have a high-quality appearance regardless of how many years it may be from today’s date. Now we have to ask the thought-provoking question: if natural stone lasts longer than its manufactured counterparts, then why?
The scientific explanation lies in the geology, chemistry, and time (millions of them).
How Natural Stone Forms
Natural stone achieves its strength through an unbelievably time-consuming process. The procedures associated with how individual stones form are unique:
Granite Formation
- Granite undergoes thousands of years of cooling deep beneath the Earth’s surface. When molten rock cools, it crystallizes. Discrete crystalline structures crystallize with the interlocking angles, allowing for the tight bonding of the elements.
Limestone and Marble Formation
- Limestone and Marble start as layers and layers of compressed organic matter that sit on the bottom of the ocean. Under immense amounts of pressure and heat, and millions of years, Limestone and Marble eventually transform into dense, near-solid rock.
The commonality between these examples is time and pressure, the “natural processes” by which we manufacture materials that last!
Consider this: manufactured stone is pressed and heated in factories for hours or days. This difference in the time it takes to form creates serious differences in durability.
The Advantage of the Crystal Structure
Here is where things get interesting from a scientific level. Natural stones can have what is referred to in geology as a “crystalline structure.” The minerals that are found in granite – quartz, feldspar, and mica – form a solid, interlocking, crystalline structure. The key difference in the crystalline structures is that the process of forming took days and weeks, respectively; these crystals formed over millions of years, allowing for strong chemical bonds between the atoms.
When viewing granite in a microscope, you are able to see these interlocking crystals fit together like a three-dimensional puzzle piece. Each piece supports the weight of its adjacent piece: the marble pieces 1607 with a strong chemical bond created by time. Therefore, when the stone experiences several kilograms of pressure horizontally, the crystalline structure distributes that stress evenly across the stone!
There may be some attempts to imitate this with manufactured stone; however, nothing can duplicate millions of years of natural crystal creation. The adhesive binders utilized in the production process typically consist of either resins or cement, which create weak points throughout the material.
The Importance of Porosity
The porosity of the unique, beautiful, and long-lasting material of natural stone is one of the many aspects that contribute to its longevity. This may be the opposite of your first thoughts, as you assumed that less porous material would make it stronger, not the case.
Natural Stone Porosity
Many natural stones are evaluated with low porosity, more uniformly. Granite typically has less than 1%. The pores are:
- Very small
- Evenly spaced apart
This low porosity allows water to access the stone, but makes it much more difficult to penetrate the stone surfaces, preventing any freeze-thaw damage to the material.
Manufactured Stone Porosity
Manufactured, engineered, or faux stone contains increased porosity, more than likely in some instances of 5-10% porosity. Not only does manufactured stone have increased porosity, but it also:
- Irregular shapes
- Connected pores
As a result of the connected pores, water can infiltrate into the material more easily, and when freezing takes place, the water will expand (and crack).
Chemical Stability over Time
Time has ensured that natural stone has survived at least millions of years of chemical weathering. The minerals that compose granite, for example, are chemically stable at Earth’s surface conditions. They have stood the tests of time in ways no laboratory could replicate.
The minerals that are composed in granite are mostly quartz, which is nearly inert and doesn’t react under any of the common chemicals you could think of in your life. The other main components are feldspar and mica, which are among the most chemically stable, relative to the common household substances we might encounter.
Manufactured stone has a binding system that doesn’t chemically have the same strength over time. Polymer resins that are common in engineered stone products have known and documented degradation, especially under:
- Extreme ultraviolet light
- High temperatures
- Certain chemicals
These engineered stone products’ binding agents ultimately are going to lose strength and deteriorate their bond of particles and agglomerates of stone.
Temperature Resistance
Natural stone will handle mechanical disruption due to thermal influences better than manufactured stone. This has to do with how it is formed and which minerals it is composed of.
Granite Temperature Advantages
Granite is the best example of all of it:
- Is formed at temperatures over 1,000°F
- Will not respond to normal daily or seasonal temperature changes inside a home or outdoor patio, or kitchen
- It contains minerals that expand and contract at the same rate, which mitigates any internal stresses on the stone
Manufactured stone typically has different rates at which the materials expand. The resin binder will expand more rapidly than the stone particles when they are heated, which, after many cycles of heating and then cooling, causes micro-cracks that will then form visible damage.
Fit for Purpose – Compression Strength
Natural stone usually has greater compression strength than manufactured stone materials and, therefore, is better able to sustain crushing forces.
Natural Stone Compression Strength
- Granite can withstand a compression force of 20,000 to 30,000 pounds per square inch (psi) • Even the most malleable of natural stones, like limestone, will be well above 10,000 psi
Natural stones get their strength from the tightly held relationships between crystalline or particle structures that have been formed over geological time. When you exert force on a natural stone, that force is distributed throughout that network of strong interconnections.
Manufactured stone has its compression strength based on the binding agent, which is often the weakest component. Even when manufactured stone has high-quality stone particles, it is impossible for the overall strength to be higher than the strength of what binds them together.
Water Absorption and Freeze-Thaw Cycles
Water damage is the number one killer of all stone installations. This is particularly true in Calgary, where the freeze-thaw cycle occurs multiple times during the winter and spring months.
Natural Stone Water Resistance
This is where the long process of formation in natural stone works to everyone’s advantage. Dense natural stones, like granite, absorb very little water — normally less than 0.4% by weight. The pore structure is tight to the grain and does not provide enough space for water to penetrate much into the material.
Once water penetrates natural stone, when it freezes, it usually expands along grain boundaries or natural weak points. Natural stone is more able to sustain it without visually damaging.
Manufactured Stone Vulnerability
Manufactured stone has a higher porosity and an interconnected pore structure, making it more vulnerable. The water is able to:
- Penetrate more deeply than natural stone
- Freeze in greater volumes
- Develop more internal pressure
- Result in more visible cracking
This is why our repair calls mostly involve manufactured stone that has been exposed to snow buildup and multiple freeze-thaw cycles.
UV Resistance and Color Stability
The colors of natural stones come from mineral inclusions that were formed under temperatures and pressures that would have made their colors unchangeable over millions of years of sun exposure.
Natural Stone Colorants
- Iron oxides produce red from granite
- Carbon compounds produce black from limestone
- Various mineral inclusions produce other natural colors
These colorants are chemically stable when exposed to UV and will not decompose or change color under long UV exposure. This UV resistance provides the capacity of natural stone to maintain its appearance for decades, even in harsh climates, while the stones are exposed to extreme sun.
Manufactured Stone Color Issues
Manufactured stone uses organic dyes or pigments in its colorant mixtures. These can fade or alter in color from UV exposure through time. Even when mineral pigment was used, it may not be as integrated into the stone structure as natural colorants have been.
Maintenance and Aging
Natural stone installations can get better with age when properly considered. Surface coatings and natural patina can surface and preserve the structure beneath. Some natural stone can become more water-resistant over time as the structure allows the natural oils, materials, etc., to fill up microscopic pores.
Longevity Advantages
In addition to this durability advantage, it allows for real longevity. Natural stone installations often last at least twice as long as manufactured alternatives. Natural stone can also restore its original appearance through acid washing, allowing the built-up debris to wash away the existing material while restoring the original color and getting rid of everything that would damage the natural stone’s structure.
Manufactured Stone Wear
Manufactured stone wear has shown up much quicker. It has:
- Bindings that can deteriorate
- Surface coatings that wear away
- Uniformity of the product highlights any damage
When manufactured stone becomes damaged, it often reveals its white cement core underneath, making repairs much more obvious and not as attractive.
This doesn’t mean manufactured stone is “bad” — it has plenty of uses and can quite easily last decades with a reasonable amount of care. However, when longevity is your true primary concern, the millions of years of “field testing” that natural stone is subjected to offers a considerable advantage over manufactured stone.
Summary
When it comes to durability, natural stone may be the best option as it has already endured millions of years of scrutiny, far more extreme than anything you would see in your home. Due to its crystalline structure, chemical stability, and method of formation, it is an entirely different material from something that can be fabricated quickly.
When you select natural stone, you are selecting a material that has withstood the test of time and one that is fundamentally different than man-made alternatives. And, you cannot beat that with even our best processes in manufacturing today.
If you are considering natural stone material for your next project, and you want professional advice on how to select and install natural stone to meet specific needs in your environmental conditions, speaking with an experienced mason can help you make the right choice for your specific needs and climate conditions.