Common Minerals that are Silicates

There are a few different varieties of minerals on our planet. One of the most popular and abundant of those varieties are those that consist of silicon and oxygen. These types of minerals are considered to be silicon dioxides or silicate minerals.

Silicate minerals are minerals that simply contain the two elements silicon and oxygen. When talking about silicate minerals, we are talking about minerals that have a chemical compound of silicon and oxygen in the form of SiO₂.

There are many minerals that are considered silicates.

Minerals that are silicates are:

Agate
Carnelian
Chalcedony
Coesite
Jasper
Keatite
Lechatelierite
Melanophlogite
Moganite
Seifertite
Stishovite
Tridymite
Quartz

Some great examples of silicon and oxygen rich material with greater amounts of other element impurities, are opal and obsidian.

A silicon and oxygen mineral is an ionic compound where there is one Si and 4 oxygens. This is an image of a silicon and oxygen tetrahedron. So why is it a SiO₂ and not a SiO₄? Simply, the oxygen molecules of the tetrahedron are shared 50/50 between 2 silicon atoms in a crystalline structure as they form a covalent bond. So each silicon atom receives half of the 4 oxygen atoms. Half of 4 is 2 and this leads to a resulting chemical formula of SiO₂.

The best and well known example of a silicate mineral is quartz. When we talk about silicon and oxygen minerals or rocks, quartz will often be part of the makeup of that mineral or rock. These silicate minerals may even be part of what is known as the quartz family. Amethyst, citrine, and smoky quartz to name a few are some examples of quartz.

Below I will describe a little about the mineral quartz and some of its varieties. We will also describe the very popular agate and carnelian to help you get an idea of these silicon and oxygen rich minerals.

Agate is a very colorful silicate mineral

Agate is a great example of a silicate mineral. Like other minerals it has impurities and is not exactly entirely composed of only these two elements. It fits into this category very well as it has a chemical composition of SiO₂. Agate is considered to be a variety of quartz

Agate is a rock consisting of chalcedony and granular quartz. During formation of agate, liquid silica materials made their way into various cracks of different volcanic rocks. Layer by layer and at times with different impurities, agate can form into a beautiful multi-colored layered gemstone.

For more information on agate you can view my article “**All About Agate**” to learn more about this silicon and oxygen rich mineral.

Carnelian is a silicate mineral with a great luster

Carnelian is a variety of chalcedony. It has the same chemical formula as other silicates, SiO₂. This mineral has impurities of iron oxide which give it its red colors. This mineral is considered to be entirely composed of silicon and oxygen despite those impurities. Carnelian is also considered to be a variety of quartz.

Carnelian is formed through the depositing of silica rich materials. The same silica rich minerals that makeup chalcedony and quartz. These liquid silica rich materials leak into cracks and pockets of igneous rocks and cool to form this silicon and oxygen rich mineral.

For more information on carnelian you can view my article “**All About Carnelian**” to learn more about this silicon rich mineral.

Quartz, the most popular silicate mineral

Quartz is what comes to a lot of peoples mind when talking about minerals with silicon and oxygen. This mineral is composed of entirely silicon and oxygen. However it has some slight variations of impurities that create a whole array of different types of quartz.

Many variations of quartz will only have 1 percent or fewer types of impurities to give it some different colors.

Amethyst – Amethyst is a quartz crystal that is purple in color. The purple color is believed to come from natural irradiation and also trace elements of iron. For more on amethyst see my article “All About Amethyst”

Citrine – This form of quartz is not common in nature. Most citrine you see out in the market is heat treated from amethyst and smoky quartz to give it that yellow look. For more information on citrine see my article at “All About Citrine”
Smoky Quartz – This quartz is a brownish grey color to black. The color is said to come from the silicon by natural irradiation.
Rose Quartz – This type of quartz exhibits a pink to red color. These colors are attributed to trace amounts of titanium, iron, and manganese. Here is a great YouTube short of a Rose Quartz Sphere.

Composed of Silicon and Oxygen, but with Other Elements

Obsidian is a great example of silicon and oxygen with some other elements in the mix. Obsidian however, is considered to be an igneous rock and not a mineral. Some will call it a mineraloid. With a chemical formula of SiO₂MgOFe₃O₄ this shows the elements of silicon and oxygen, but also other abundant elements as well.

For more information on obsidian you can view my article “**All About Obsidian**” to learn more about this silicon rich igneous rock.

Opal is a mineral with a unique way of expressing color. It is not composed entirely of silicon and oxygen, but its formation of silicon makes it very unique. Opal has a chemical formula of SiO₂·nH₂O and the impurities within that formula are not what makes opal express its many different eye appealing colors.