What Common Rocks Composed Of
We see plenty of common looking rocks everywhere. Some have very interesting looking patterns, while others don’t look like much at all. Rocks however, are very import in our daily lives no matter how common they look and it all stems from the contents within them.
Most common rocks will be composed of oxygen and silicon. This leads to many rocks containing silicon dioxide type minerals within them. Many common rocks will also contain elements such as aluminum, calcium, iron, potassium, magnesium, and sodium.
These common ingredients in our rocks are part of the make up for the most common minerals on earth which are quartz and feldspar. Which are silicon dioxide minerals.
Common rocks are formed by the repeating process of the rock cycle. All rocks you see around you, common or not, have all been formed through the rock cycle process. This cycle of forming rocks has been essential to the renewal of rocks, and their contents, for many years.
See reference below for rocks changing within the rock life cycle.*
The Most Common Rocks
The most common rocks you find on earth will be sedimentary rocks. This is because erosion and weathering on the surface of our earth will break down all rocks and turn them to sedimentary rocks over time. When you go deeper within the earth, this changes.
See Reference below for explanation on weathering.*
Igneous and metamorphic rocks will be far more abundant than sedimentary rocks as you go deeper within the earth. This however does not mean that sedimentary rocks cannot be deeper in the earth. Sedimentary rocks can be deep in the earth but will become more susceptible to change.
Limestone is one of the most common rocks you will find on the surface of the earth. This type of rock can contain quite a bit of silica and oxygen, as we know it is the most abundant. The formation of sedimentary rock is quite possibly one of the most important aspects in the rock life cycle.
By common rocks breaking down and then settling somewhere to form sedimentary rocks, you end up creating new combinations of material in the rock. Contents from mountains separated by great distances, can find their way into lakes miles away. This creation of new mixtures will overtime be pushed deep into the earth to be transformed in the rock cycle.
Common Rocks in My Backyard Also Contain Silicon and Oxygen
Oddly enough, many of the common rocks you find in your backyard are not the expected sedimentary rocks that make up a majority of the surface of our earth. These rocks, which may often be landscaping rocks, are igneous or metamorphic rocks. Igneous and metamorphic rocks tend to be more durable when it comes to landscaping and used as ground covering.
That is not to say that sandstones and limestones are not commonly used in landscaping. In fact they are used quite often. Many of their applications though are in the form of carved out benches, large display pieces, or even walking paths.
Sand or soil will likely be the most abundant thing in your backyard. This substance is considered more so as sediment, rather than rocks. However, every so often you can find a pebble or larger rock in the contents of your soil or sand. These rocks will often be a metamorphic or igneous rock.
In all, the common occurrence of rocks in any form, even soil in your backyard, will likely have high contents of silicon and oxygen.
The Contents of Metamorphic Rocks
Metamorphic rocks are made by the contents of other igneous and sedimentary rocks. This means metamorphic rocks are made of an abundance of common elements such as silicon and oxygen. These types of rocks are altered by heat and pressure and also the injection of possible new elemental contents deep in the earth.
See reference below on more content about metamorphic rocks.*
The Contents of Igneous Rocks
Common igneous rocks will contain much of what sedimentary or metamorphic rocks have. Igneous rocks are made of an abundance of silicon and oxygen as well as other common elements. One of the enjoyments of igneous rocks is that they often contain many different and visible crystal minerals.
The most common of the crystal minerals within igneous rocks is what you would guess, quartz. Which is a silica oxygen mineral. Often other trace elements such as iron or magnesium will mix into the creation of these minerals within igneous rocks.
This will lead to some very different colorful results such as citrine and amethyst. Not all quartz minerals within igneous rocks look like citrine or amethyst crystals though. Additionally, other minerals in the quartz family such as jasper, agate, and carnelian will be contained within igneous rock and they look nothing like quartz crystals.
See reference below on more content about igneous rocks.*
Common Rocks and Minerals Together
It is important to note that common rocks are not made of minerals. Rocks are made up of elemental contents and can contain one or more minerals within them. Rocks will often contain the elemental contents of silica and oxygen to produce minerals such as quartz, feldspar, calcite, olivine, and mica within it.
I often feel I need to reiterate that point as it often gets lost in many discussions across the internet. Rocks and minerals are separate, and having them this way helps classify and identify things better in the geology world.
Conclusion
The common rocks on our earth are made up of mostly silicon and oxygen. There are many other elements available within rocks, but not to the abundance of these two elements.
The three types of rocks, sedimentary, metamorphic, and igneous, will contain mostly silicon and oxygen with other trace elements. These three rock types, with long amounts of time, will change through the rock cycle.
However, those silicon contents along with oxygen with often not diminish but transform within the cycle including all other elements within our earth.
References:
* The Rock Cycle is where rocks will undergo transformation into one of the three types of rocks over long periods of time. It’s like a big process of renewal for our earth. See my article “Diagram of the Rock Cycle” for more details.
* Weathering is where rocks will break down into smaller pieces. Weathering and erosion is why sedimentary rocks make up most of the rocks on our surface. However weathering and erosion are not considered the same. See my article “The Breaking Down of Rocks by Weathering”.
* Metamorphic rocks are altered rocks from igneous and sedimentary rocks. See my article for more detail and understanding of metamorphic rocks “What are Metamorphic Rocks”.
* Igneous rocks are molten magma cooled down. This rock can only be called igneous if it was directly formed from cooled off magma. See my article “What are Igneous Rocks” for more details.
