The element silicon

Silicon is a chemical element with the atomic number 14. It is abbreviated to the symbol “Si” in the periodic table of elements and is one of the classic metalloids. Pure silicon is a gray-black color and has the typical shiny metallic sheen of metals. Due to its chemical properties, it is used in industry for the manufacture of electronic components (e.g. microchips and processors).

However, it is also used in many other industrial applications. As silicates, minerals, or silicon dioxide, predominantly quartz, it is used to make glass, cement, and ceramics, and constitutes the main component of these products.

Silicon deposits

The natural deposits on earth are very large. After oxygen, silicon is the second most abundant element in the earth’s crust and is present everywhere, making up approximately 28 percent by weight of the earth’s mass. Even in space, silicon is the 8th most common element by mass. Earth-like planets all largely consist of silicates.  It can be found in dust, sand, rocks, and planet mass in various forms of silicates and silicon oxide compounds.

Silicon reacts very easily with oxygen, which is why it is only rarely found in its pure form on earth. It mostly occurs as highly stable silicate minerals and silicon oxides. Sand made up of silicon dioxide is everywhere and can be found in the upper crust of the Earth due to its hardness, chemical resilience, and resistance to weathering.  In its pure form, silicon dioxide, with traces of a wide range of mineral substances, creates characteristic quartzes, which are known as different gemstones (e.g., amethyst, rose quartz, agate, and opal). The finest quartzes are the precious stones emerald and aquamarine. With many metals, silicon forms silicates (salts of silicic acid Si(OH)4). The earth’s crust comprises 90% silicates and the mantle is made up almost entirely of silicates, and it is also a component of rocks. The most common silicates are feldspars, followed by minerals such as mica, clay, shale, sandstone, and garnet etc... Silicon compounds are not only found in solid form on Earth. A large proportion of natural silicon is dissolved in the oceans as monomeric silica. The oxyacids of silicon are called silicic acids. The simplest acid is monosilicic acid (orthosilicic acid), which can be found in all bodies of water, including drinking water, as well as in animal and plant fluids. The concentration of dissolved silicon in water depends on geographical and geological environmental features because it is dissolved from rocks and the soil by weathering and then enters water and drinking water.

Silicon in nature

Silicon occurs in nature in large quantities in silicate compounds. However, it is only absorbed and used directly by only a few organisms, which form siliceous structures. They include diatoms, radiolarians, and some sponge species. With the aid of special enzymes, they form silicon oxide-containing exoskeletons.  In the plant world there are also species that utilize the special properties of silicon. Horsetail and bamboo plants are rich in silicon dioxide in their leaves and stems. These plants form a silicon dioxide framework, which makes them particularly stable without affecting their flexibility

In general, all plants absorb and store silicon as they grow. Many plants accumulate silicon from the soil, or from earthy solutions, and use it as a structure-forming element, e.g. to stabilize the plant stem. High levels of silicon are found particularly in cereals and grasses. When raw products are processed into food, a large part of the silicon content is removed, meaning that it is no longer available.

Silicon in the human body

The human body contains approximately 1 g to 2 g of silicon, which makes it the third most common trace element in the body after iron and zinc (physiologically important trace elements). Despite the high proportion of silicon in the human body, its precise role has not yet been fully explained. It was initially thought that silicon had no particular function in the body. However, animal studies performed since the 1970s show changes to the connective tissue and bones in cases of diet-related silicon shortage.

As the body can only obtain silicon from food, it is called an essential mineral. Thus, the body depends on the food intake containing enough silicon in a form that can be used by the body.