How do Minerals Form?
Minerals that make up moon rocks are the same minerals that are found on Earth. Some moon rocks have minerals that combine to form kinds of rocks that are not found on Earth. Apr 10, †Ј The silica tetrahedron is a very strong and stable combination that easily links up together in minerals, sharing oxygens at their corners. Isolated silica tetrahedra occur in many silicates such as olivine, where the tetrahedra are surrounded by iron and magnesium alldatingloveen.comted Reading Time: 3 mins.
Home Mineralogy Rocks. Combinations of common minerals occur in different kinds of rocks. The kind of rock depends on the geologic setting where they form: igneous, sedimentary, or metamorphic. The mineral composition of a rock reflects the physical environment and geologic history where a rock formed. Rock form in a variety of geologic setting ranging from locations on or near the earth surface, deep underground, or even in outer space.
Most of the rocks we see on the surface of the planet formed by processes that happened long ago, but we can see these processes actively taking place in many places. Rapid rock formation can be seen happening such as lava cooling from a volcanic eruption in places like Hawaii or Iceland. However, most rocks we see around us form very slowly in settings that are not visible on the land surface.
Slow processes combinex rocks can be inferred by observing reefs growing in the oceans, or sediments being carried by flowing water in streams or moved by waves crashing on beaches.
We can see sediments being deposited, but we cannot see them turning into stone because the process may what does the candles on the menorah symbolize thousand or even millions of years. While rocks consist of aggregates of minerals, minerals themselves are made up of one or a number of chemical elements with a definite chemical composition.
Minerals cannot be broken down into smaller combunes with different chemical compositions combies the way that rocks can. More than two thousand three hundred different types of minerals have been identified. Luckily many are rare and the common rocks are made up of a relatively small number of minerals. Share to:.
Combinations of common minerals occur in different kinds of rocks. The kind of rock depends on the geologic setting where they form: igneous, sedimentary, or alldatingloveen.comted Reading Time: 3 mins.
The vast majority of minerals in the Earth's rocks, from the crust down to the iron core, are chemically classed as silicates. These silicate minerals are all based on a chemical unit called the silica tetrahedron.
The two are similar, but neither should be confused with silicone , which is a synthetic material. It is the seventh most abundant element in the universe. Silica is an oxide of siliconЧhence its other name, silicon dioxideЧand is the primary component of sand.
The chemical structure of silica forms a tetrahedron. It consists of a central silicon atom surrounded by four oxygen atoms, with which the central atom bonds. The geometric figure drawn around this arrangement has four sides, each side being an equilateral triangleЧa tetrahedron.
To envision this, imagine a three-dimensional ball-and-stick model in which three oxygen atoms are holding up their central silicon atom, much like the three legs of a stool, with the fourth oxygen atom sticking straight up above the central atom. Chemically, the silica tetrahedron works like this: Silicon has 14 electrons, of which two orbits the nucleus in the innermost shell and eight fill the next shell.
The four remaining electrons are in its outermost "valence" shell, leaving it four electrons short, creating, in this case, a cation with four positive charges. The four outer electrons are easily borrowed by other elements. Oxygen has eight electrons, leaving it two short of a full second shell. Its hunger for electrons is what makes oxygen such a strong oxidizer , an element capable of making substances lose their electrons and, in some cases, degrade.
For instance, iron before oxidation is an extremely strong metal until it is exposed to water, in which case it forms rust and degrades. As such, oxygen is an excellent match with silicon. Only, in this case, they form a very strong bond. Each of the four oxygens in the tetrahedron shares one electron from the silicon atom in a covalent bond, so the resulting oxygen atom is an anion with one negative charge.
Therefore the tetrahedron as a whole is a strong anion with four negative charges, SiO 4 4Ч. The silica tetrahedron is a very strong and stable combination that easily links up together in minerals, sharing oxygens at their corners.
Isolated silica tetrahedra occur in many silicates such as olivine, where the tetrahedra are surrounded by iron and magnesium cations. Pairs of tetrahedra SiO 7 occur in several silicates, the best-known of which is probably hemimorphite.
Rings of tetrahedra Si 3 O 9 or Si 6 O 18 occur in the rare benitoite and the common tourmaline, respectively. Most silicates, however, are built of long chains and sheets and frameworks of silica tetrahedra. The pyroxenes and amphiboles have single and double chains of silica tetrahedra, respectively. Sheets of linked tetrahedra make up the micas , clays, and other phyllosilicate minerals.
Finally, there are frameworks of tetrahedra, in which every corner is shared, resulting in a SiO 2 formula. Quartz and the feldspars are the most prominent silicate minerals of this type. Given the prevalence of the silicate minerals, it is safe to say that they form the basic structure of the planet. Share Flipboard Email. Andrew Alden. Geology Expert. Andrew Alden is a geologist based in Oakland, California. He works as a research guide for the U. Geological Survey. Updated April 10, Cite this Article Format.
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