Silica sand, which is a naturally occurring type of sand that contains crushed particles of quartz, has a wide variety of industrial applications. Experts value silica sand’s hardness, chemical inertness, and high melting point and it serves as the primary component in the production of diverse products such as glass, ceramics, and concrete.
Silica sand’s versatility extends beyond its elemental composition. Innovators and artists use silica sand in its granular form for such purposes as an integral part of water filtration, hydraulic fracturing, and artistic expression. As one of the most abundant minerals on the earth, industries will continue to find ways to use silica sand which will drive technological advancement in multiple disciplines.
What is Silica Sand?
Silica sand is a granular material composed primarily of silicon dioxide (SiO2) that is present in the form of quartz crystals. It is one of the most common types of sand in the world. Silica sand forms as a result of the erosion of rocks containing quartz.
Silica sand has chemical and physical properties that are valuable in the industrial world, including a high melting point, resistance to chemical reactions, strength, hardness, transparency, and excellent thermal stability. Manufacturers not only prize sand for its properties but because of its low cost and abundance.
Silica sand also has qualities that have disadvantages in particular applications. Some of these include a high rate of thermal expansion, low thermal conductivity, and the release of silica particles during the mining or handling of silica sand, which can cause respiratory risks for workers.
Sources of Silica Sand
Manufacturers source silica sand from various geological locations and use diverse methods. These elements affect the quality of the silica sand regarding its purity and particle size. This can also determine whether or not the silica sand is taken in a sustainable manner and with regard to its environmental impact.
- Sand mining – Traditional sand mining techniques are common for the extraction of silica sand. Miners gather silica sand from sand deposits on the earth’s surface or dig below the earth using open-pit or dredging methods.
- Quarries – Manufacturers also source silica sand from quarries, where they extract the silica sand from rock formations with high amounts of quartz. Quarrying involves drilling, blasting, and crushing the rocks to produce silica sand.
- Beach and coastal sand – In some regions, silica sand is a natural deposit along certain beaches and coastal areas. Natural processes including waves and wind action that causes erosion create the build-up of granular particles in these areas.
- Alluvial deposits – Silica sand is common in alluvial deposits, which are sedimentary deposits along the edges of rivers and streams. Over time, these deposits gather large quantities of silica sand which is collected and processed to rid the mix of other impurities.
- Industrial processes – Some industrial processes, including quarrying or mining for other minerals, can generate silica sand as a by-product. In these cases, manufacturers gather the silica sand and use it in other applications.
Properties of Silica Sand
Silica sand, also known as industrial sand, has many properties that translate to important usage in a wide variety of industries.
Silica sand’s primary element is silicon dioxide (SiO2) with around 95% purity. This means that it contains silicon dioxide and is largely free from impurities contained in other types of sand including elements like clay, silt, iron, mica, feldspar, and organic matter.
High purity is essential in applications like glassmaking, metal casting, and electronics production where the impurities can have an adverse effect on the look and behavior of the resulting products.
Silica sand contains a high level of quartz, which brings an impressive hardness to the sand particles. Quartz has a level of hardness right below stainless steel, which is higher than many minerals that exist in other types of sand. Hardness brings a high level of durability in abrasive silica sand applications like sandblasting, grinding, and polishing.
Low Thermal Conductivity
Silica sand exhibits low thermal conductivity, which means that it does not conduct heat well. This makes it less reliable in certain metal casting applications but means that it is well-suited as a heat insulator. Many foundries use silica sand as an insulating material for refractory material or in foundry molds.
High Coefficient of Thermal Expansion
Silica sand has a high thermal expansion which means that it expands and contracts in response to changes in temperature. This is a disadvantage in metal casting using metals with high melting points where the movement can cause defects.
Silica sand is chemically inert, which means that it does not chemically react with most substances. This property makes it ideal in environments with high chemical exposure or extreme weather, where other substances might corrode or degrade.
Uniform Particle Size Distribution
Sand particles range in size from 1/16 mm-2 mm. Silica sand is graded to have a uniform particle size distribution. This size distribution is a vital characteristic that manufacturers need to know when choosing a specific granule size for their application. The precise particle size distribution is vitally important in certain applications including water filtration, hydraulic fracturing, foundry casting, and glassmaking.
Translucency and Clarity
The translucency and clarity of silica sand are related properties. Translucency means the ability of silica sand to allow light to pass through it. The clarity of silica sand means that it can transmit light through it with minimal distortions. The high quartz content of silica sand means that it has both high levels of translucency and clarity. These levels are impacted by the level of impurities in the sand, which is the reason glassmakers require between 95%-99% pure silica sand. Clear glass requires the most pure silica sand.
Silica sand is one of the most abundant materials on the Earth and it has a wide geographic distribution, which means that you can find it in locations all over the world. The abundance of the material keeps the cost of silica sand low, but the exact cost of silica sand depends on the manufacturing process and purity of the sand.
The use of silica sand has many environmental benefits including that it is naturally sustainable. Silica sand is naturally abundant and is consistently renewed through natural processes. Silica sand also has a lower environmental impact than other construction materials because it requires minimal production processes from sourcing to distribution. Silica sand components like foundry molds and construction materials can often be recycled.
Silica sand particles are broken down during sourcing, processing, or industrial applications. These can generate fine silica particles, known as respirable crystalline silica, with a diameter of 2.5 micrometers or smaller. These are easily inhaled and can enter the lungs. These particles can cause significant damage to the lungs, which can lead to silicosis, lung cancer, chronic obstructive pulmonary disease, and tuberculosis.
Type and Uses of Silica Sand
There are various types of silica sand and the qualities that differentiate them make them usable for specific applications.
Regular Silica Sand
This is the most common type of silica sand. It has a well-graded particle size distribution ranging from coarse to fine. Its primary component is silica which makes up around 95% of its total composition. Impurities like alumina, iron, and lime make up the other 5%.
- Uses: Landscape and decorative projects, industrial sandblasting, cementitious grout, sports field infill, construction fill material
Industrial Silica Sand
Industrial silica sand is characterized by high levels of pure silica, with minimal impurities. This ensures that it meets quality standards for a variety of specialty applications.
- Uses: Glassmaking, ceramics, fiberglass, filler in paints, coatings, and rubber products
Very-Fine Silica Sand
Very-fine silica sand has a consistent particle size distribution between 0.06 mm-1 mm. Very-fine silica sand is also characterized by a high degree of purity.
- Uses: High-performance concrete, refractory materials, oil and gas well cement, polymer composites, nanotechnology, high-performance coatings, electronics
Water Filtration Silica Sand
Water filtration sand is produced to control for a uniform particle size distribution, high purity, and rounded shape. This type of sand is effective for removing impurities from the water as it flows through the sand particles.
- Uses: Drinking water filtration, swimming pool filtration, industrial water treatment, wastewater treatment, groundwater remediation, desalination.
Turf Silica Sand
Turf silica sand is an infill sand that is manufactured for use in artificial turf systems. It stabilizes and supports turf systems. It has a coarser particle size than regular silica sand to ensure proper drainage. Turf sand has a rounded shape to minimize the possibility of abrasions and a high level of purity to enhance the appearance of the sand.
- Uses: Infill and decorative sand for sports and recreation turf areas
Frac Silica Sand
Frac silica sand is used in specialized drilling techniques for oil and gas. Frac sand is characterized by a very high degree of purity (over 99% silica), which is vital for protecting oil and gas from contamination. It also has a specific rounded shape, uniform particle size, and crush resistance.
- Uses: Hydraulic fracturing, frac sand mining
Foundry Silica Sand
The metal industry uses foundry sand to create molds and cores for metal casting. Foundry sand has both coarse and fine sand particles to allow for good compaction. It also has a high level of purity, from 95%-99% depending on the type of metal being cast and a low moisture content.
- Uses: Mold-making, core-making, no-bake casting, lost-wax casting