Silica, or silicon dioxide (SiO2), occurs in the Earth’s crust, the microcosm and daily life. Silica makes ancient glass such as obsidian, and beautiful gemstones. It's essential for environmental health. Here are the facts about silica.
Silica, or silicon dioxide (SiO2), is a naturally occurring compound of silicon and oxygen. It manifests in countless forms, from micro-crystalline silica to quartz or rock crystal. Silica is widely recognized for durability.
Forms such as-crystalline, amorphous, and granular make this compound a key building block in many geological processes. It's essential in products from glass and ceramics to food additives. Silica is in over 80% of modern glass formulas.
Properties of Silica
Chemical Stability: It is highly resistant to chemical weathering. Silica sand is used in landscaping and construction for this reason.
Hardness: Silica ranks 7 on the Mohs hardness scale, making it one of the hardest substances.
High Melting Point: It has a melting point around 1,600 degrees Celsius (2,912 degrees Fahrenheit), which allows it to withstand extreme temperatures.
Transparency: In its crystalline form, quartz can be transparent to translucent, making it valuable in optics. The crystalline form of silica can be transparent and has the ability to refract light, important in lenses.
Hardness: Silica ranks 7 on the Mohs hardness scale, making it one of the hardest natural materials. This quality makes it desirable for abrasive products.
Absorbent: Amorphous silica has excellent absorbent properties, making it useful in products ranging from cat litter to food preservation.
Silica in Nature
Silica is ubiquitous in nature, found in formation of rocks, soils and living organisms. It forms the primary component of sand. It's integral to the creation of many plants by silicification, in which silica is deposited in cell walls, enhancing structure and resistance to pests.
It appears in familiar forms such as quartz, sand and opal. It creates the famous rhinestones of Germany and Austria. Silica is essential to natural systems.
In geology, silica contributes to formation of rocks and supports soil health, fundamental in agriculture. For plants, silica helps strengthen cell walls, reducing susceptibility to pests and droughts. It's a natural abrasive in erosion.
Diatoms are known for their fantastic shells of silica. These microscopic algae can appear in tapered form as below, rectangular form. Several diatomaceous algae can also create intricate patterns by linking together.
Ancient Use of Silica
It's a main component of natural glass like obsidian, moldavite and Libyan desert glass. The latter two are thought formed millions of years ago from intense heat of a meteorite impact. These are treasured in jewelry and ornament. Libyan desert glass appears in Egyptian tombs.
Structures of fused silica are also created by lightning strikes, or as below by a power line arcing over rocky soil. Lechatelierite is the mother of lightning glass stones, in that all lightning glass is a type of this formation.
Egyptian faience is a type of frit glass highly popular on trade routes. Frit is a mixture of quartz (silica), alkali such as natron or plant ash, and lime with a copper or cobalt colorant to give a coveted blue color.
Faience is created by crushing quartz or sand crystals. Artisans mix them with varying quantities of sodium, potassium, calcium, magnesium, and copper oxide. This mixture is then shaped into the desired form, such as an amulet, beads, a brooch, or a figurine.
It's then given a high heat treatment. Glaze colors range from translucent earth brown tones to green, aqua and brilliant blue. Deep blue faience resembles the color of desirable gemstone lapis lazuli.
Earliest evidence of faience production comes from a workshop c. 5200 BCE, located near the temple of the god Khentiamentiu in Abydos. Examination of plant ash identifies the time period.
Quartz or rock crystal is known to ancient Greeks as krystallos, meaning crystal. The natural historian Pliny the Elder in 1st century Rome posits clear quartz is water frozen so long it's become stone. Amethyst, a type of quartz, is highly prized in Rome.
Early humans use microcrystalline silica in the form of flint to create tools and weapons. It's prized for hardness and ability to produce sharp edges. Accurate knapping techniques can craft effective weapons, hunting and cutting tools.
The natural volcanic glass obsidian is up to 80% silica. Neolithic trade routes are set up around the raw and processed forms of this desirable product.
Silica-rich clay is used for pottery, providing a durable, fire-resistant medium. As well, ancient Egyptians use silica in sand to create mortar for statues and buildings. Ancient Egyptians are responsible for many progressive ideas in science, before the official existence of science.
Gemstones: Silica and Chalcedony
Silica acts as a parent compound to various gemstones, including the many types of chalcedony. Chalcedony is a microcrystalline type of silica forming in layered deposits with unique color variations and patterns, as in the many types of agate.
As a gemstone, chalcedony is valued for ornamental properties and is frequently used in jewelry. Types of chalcedony include carnelian, chrysoprase and onyx. Both silica and chalcedony are composed of silicon dioxide, but they differ in structure.
Silica Modern Discovery
Advances in the study of silica occur during the 18th century when scientists began to isolate and analyze its purity and crystalline structure. At this time in history chemists are trying to distance themselves from alchemists, who have gained an unsavory reputation.
Jöns Jakob Berzelius (1779 - 1848), a Swedish chemist, is one of the first to isolate silica in its purified form. His findings help clarify the occurrence of silica in nature and its significance in chemistry.
Silica in Industry
Silica has extensive industrial applications, including:
Construction: Silica is a primary ingredient in concrete and cements. Approximately 70% of concrete's composition is silica.
Glass Manufacturing: It's the main component in glass production.
Electronics: High-purity silica is crucial in the manufacture of semiconductors.
Ceramics: Silica is used to provide strength and heat resistance to ceramic products.
Food: Silica is used as a flow agent in powdered foods and supplements, and to clarify beverages.
Cosmetics: Micronized silica improves the texture of cosmetics, creating a smoother finish and enhancing aesthetic appeal in skincare products.
Edibility of Silica
Silica itself is not considered toxic and occurs naturally in many foods. However, the ingestion of silica in large, pure forms (like raw sand) can pose health risks. Food-grade silica, often used as an additive, is deemed safe for consumption in moderate amounts.
Silica Dust
Inhalation of silica dust can cause lung cancer, silicosis (a permanent scarring and hardening of the lungs), kidney disease, and chronic obstructive pulmonary disease. Annually, about 230 people develop lung cancer due to previous occupational exposure to silica dust.
Modern Uses of Silica
In contemporary society, the applications of silica continue to expand. Its use in advanced technologies such as nanotechnology, solar cells, and high-performance materials is on the rise. Silica nanoparticles are also being explored for use in drug delivery and as antimicrobial agents.
Nanotechnology: Silica nanoparticles are increasingly important in drug delivery and medical imaging, offering innovative solutions in healthcare.
Solar Panels: Silicon derived from silica is essential in solar panel manufacturing, with about one-third of the world’s energy now generated from solar technology.
Water Filtration: Silica is frequently used in water treatment systems, helping to ensure access to clean drinking water, affecting billions globally.
Facts About Silica
Abundance: Silica is the most abundant mineral in the Earth's crust, comprising about 59% of its weight. Silica is the second most abundant mineral in the universe.
Health Risks: While silicon itself is not hazardous, inhaling fine silica dust (crystalline silica) can lead to respiratory issues, including silicosis.
Natural Habitat: It is naturally present in soils, an essential component of agriculture and plant ecology.
Silica can form naturally occurring structures like siliceous sinter, an opaline deposit of geyserite, typically found in geothermal areas.
Silica (SiO2) is an integral compound and has shaped nature and society from ancient tools to advanced industrial applications. Whether in its natural form or as part of a manufactured product, silica continues to spark innovation and drive industries forward.
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