Silicate minerals facts for kids

This is chrysocolla, a copper silicate mineral.

Silicate minerals are a huge group of minerals that make up most of the Earth's crust—about 90 percent! They are called "silicates" because they are built from special groups of silicon and oxygen atoms. These minerals are found everywhere, from the rocks in mountains to the sand on beaches.

One very common silicate mineral is quartz. You might know it as the main part of sand. Quartz is a form of silicon dioxide (SiO₂), which is also considered a silicate.

Silicate minerals form in many ways over billions of years. This includes processes like rocks melting and then cooling, changing under heat and pressure (metamorphism), and breaking down from weather.

Tiny diatoms, seen under a microscope, build their shells from silica.

Even living things help create silicates! For example, tiny ocean creatures called diatoms build their hard outer shells from silica they take from seawater. When these diatoms die, their shells sink and become a big part of deep ocean sediment. This sediment can eventually form a soft rock called diatomaceous earth.

What are Silicate Minerals Made Of?

Most silicate minerals are ionic compounds. This means they are made of atoms with electrical charges. The main parts of these minerals are groups of silicon and oxygen atoms.

Imagine a silicon atom in the middle, surrounded by four oxygen atoms. This shape is called a tetrahedron, like a small pyramid. These silicon-oxygen pyramids are the basic building blocks of all silicate minerals. Sometimes, two pyramids can share an oxygen atom, connecting them together. If an oxygen atom isn't shared, it has a negative charge, which helps balance the mineral's overall charge.

Sometimes, other atoms, like aluminum, can take the place of a silicon atom in these pyramids. When this happens, it can change the mineral's charge. For example, in a mineral called orthoclase, aluminum atoms replace some silicon atoms. This gives the mineral a negative charge, which is then balanced by positive potassium atoms.

How Do We Group Silicate Minerals?

Scientists group silicate minerals based on how their silicon-oxygen pyramids are connected. There are seven main groups:

For tectosilicates, if some silicon atoms are replaced by other atoms like aluminum, the mineral might need extra positive atoms to balance its charge.

Nesosilicates: The "Island" Silicates

Nesosilicate minerals on display.

This shows a single silicon-oxygen pyramid (tetrahedron). The grey ball is silicon, red balls are oxygen.

Nesosilicates (from the Greek word for "island") have silicon-oxygen pyramids that are completely separate from each other. They are like tiny islands connected only by other atoms that hold them together.

Some examples of nesosilicates include:

• Olivine group: Like Forsterite (Mg₂SiO₄) and Fayalite (Fe₂SiO₄).
• Garnet group: Such as Pyrope (Mg₃Al₂(SiO₄)₃) and Almandine (Fe₃Al₂(SiO₄)₃).
• Zircon group: Including Zircon (ZrSiO₄).
• Al₂SiO₅ group: Like Andalusite, Kyanite, and Sillimanite.

Kyanite crystals.

• Topaz (Al₂SiO₄(F,OH)₂).

Sorosilicates: The "Heap" Silicates

Sorosilicate minerals at a museum.

This image shows two silicon-oxygen pyramids joined together.

Sorosilicates (from the Greek word for "heap" or "mound") have silicon-oxygen pyramids that are joined in pairs. They share one oxygen atom, forming a double pyramid structure.

Examples of sorosilicates are:

• Hemimorphite (Zn₄(Si₂O₇)(OH)₂·H₂O).
• Lawsonite (CaAl₂(Si₂O₇)(OH)₂·H₂O).
• Epidote group: Such as Epidote (Ca₂(Al,Fe)₃O(SiO₄)(Si₂O₇)(OH)) and Zoisite (Ca₂Al₃O(SiO₄)(Si₂O₇)(OH)).

Cyclosilicates: The "Ring" Silicates

Cyclosilicate minerals.

Pezzottaite is a cyclosilicate.

Cyclosilicates (from the Greek word for "circle") have silicon-oxygen pyramids linked together in rings. These rings can have different numbers of pyramids, like 3, 4, 6, or even 9.

Some examples of cyclosilicates include:

• Benitoite (BaTi(Si₃O₉)), which has 3-member rings.
• Beryl (Be₃Al₂(Si₆O₁₈)), a well-known gemstone, has 6-member rings.
• Tourmaline (a complex mineral with 6-member rings).
• Cordierite ((Mg, Fe)₂Al₄Si₅O₁₈).

Inosilicates: The "Chain" Silicates

Inosilicates (from the Greek word for "fibre") have silicon-oxygen pyramids linked together to form long chains. These can be single chains or double chains.

Single Chain Inosilicates

These minerals have a single line of silicon-oxygen pyramids linked together.

• Pyroxene group: A very common group of minerals. Examples include Enstatite (MgSiO₃), Diopside (CaMgSi₂O₆), and Jadeite (NaAlSi₂O₆).
• Wollastonite (CaSiO₃).
• Rhodonite (MnSiO₃).

Double Chain Inosilicates

These minerals have two parallel chains of silicon-oxygen pyramids linked together.

• Amphibole group: Another very common group. Examples include Anthophyllite (Mg,Fe)₇Si₈O₂₂(OH)₂, Tremolite (Ca₂Mg₅Si₈O₂₂(OH)₂), and Hornblende (a complex amphibole).

Phyllosilicates: The "Sheet" Silicates

Kaolinite is a type of clay mineral.

Phyllosilicates (from the Greek word for "leaf") form flat, parallel sheets of silicon-oxygen pyramids. Because of this sheet-like structure, many of these minerals can be easily split into thin layers, like the pages of a book. All phyllosilicates contain water or hydroxyl (OH) groups.

Some examples of phyllosilicates are:

• Serpentine subgroup: Including Antigorite and Chrysotile (Mg₃Si₂O₅(OH)₄).
• Clay minerals: Such as Kaolinite (Al₂Si₂O₅(OH)₄) and Montmorillonite (a type of swelling clay).
• Talc (Mg₃Si₄O₁₀(OH)₂), which is very soft.
• Mica group: Like Biotite (K(Mg,Fe)₃(AlSi₃)O₁₀(OH)₂) and Muscovite (KAl₂(AlSi₃)O₁₀(OH)₂).
• Chlorite group: A common group found in metamorphic rocks.

Tectosilicates: The "Framework" Silicates

The 3D structure of beta-quartz.

A beautiful quartz crystal.

This rock, collected from the Moon, contains plagioclase feldspar.

Tectosilicates, also called "framework silicates," have silicon-oxygen pyramids connected in a complex, three-dimensional network. This group makes up almost 75% of the Earth's crust!

Most tectosilicates also contain aluminum atoms mixed in with the silicon.

Important examples include:

• Quartz family: All forms of SiO₂, like Quartz itself, Tridymite, and Cristobalite.
• Feldspar group: These are the most common minerals in the Earth's crust.

* Alkali feldspars: Such as Orthoclase (KAlSi₃O₈). * Plagioclase feldspars: A series of minerals ranging from Albite (NaAlSi₃O₈) to Anorthite (CaAl₂Si₂O₈).

• Feldspathoid family: Minerals like Nepheline ((Na,K)AlSiO₄) and Sodalite (Na₈(AlSiO₄)₆Cl₂).
• Zeolite family: These minerals have open structures with channels, which allows them to absorb water. Examples include Natrolite (Na₂Al₂Si₃O₁₀·2H₂O) and Chabazite (CaAl₂Si₄O₁₂·6H₂O).

Images for kids

• 

  6 units [Si
  6O
  18], beryl (red: Si, blue: O)

• 

  3 units [Si
  3O
  9], benitoite

• 

  4 units [Si
  4O
  12], papagoite

• 

  9 units [Si
  9O
  27], eudialyte

• 

  6 units, double ring [Si
  6O
  15], milarite

• 

  Inosilicate, pyroxene family, with 2-periodic single chain (Si
  2O
  6), diopside

• 

  Inosilicate, clinoamphibole, with 2-periodic double chains (Si
  4O
  11), tremolite

• 

  Inosilicate, unbranched 3-periodic single chain of wollastonite

• 

  Inosilicate with 5-periodic single chain, rhodonite

• 

  Inosilicate with cyclic branched 8-periodic chain, pellyite

See also

In Spanish: Silicato (mineral) para niños