In this article, you will learn about different types of rocks and distinguish limestone from sandstone. There are three main types of rocks. Metamorphic, sedimentary and Igneous are different types of rocks. We’re now going to look at these types more closely.
Some rocks might be new to you. You can find many of these rocks in your neighborhood. Classification of rocks is done based on how they are formed. When we look at rocks we talk about a few things.
We talk about hardness, cleavage, or how the rock splits. Luster or how shiny it is. Color streak or the color of the powder left when a rock is rubbed against porcelain and texture or the feel or the appearance of the rock. Let us learn about three different types of rocks.
3 types of rocks
Igneous rocks
Igneous rocks form once magma cools as they crystallize from a liquid called molten rock. Mainly there are two types of igneous rocks. Extrusive and intrusive.
Intrusive igneous form when magma cooled inside underneath the Earth’s surface because they cool off slowly. These types of rocks form a texture like granite. granite has a speckled appearance because it consists of different minerals in the rock.
When magma cools outside of the volcano on the exterior of the earth it forms extrusive igneous. This type of rock made from the lava has fine grains and hardly any crystals. Volcanic rocks are the other name for Extrusive igneous rocks.
Let’s take a look at how intrusive and extrusive rocks differ in terms of what they form from, where they are created, and the rate of cooling.
Molten rocks found on the surface intrusive rocks are created from magma which is a molten rock found inside the earth. Extrusive rocks are created on the surface where molten rock has flown.
Intrusive rocks are created inside the earth from hot magma. Extrusive rocks cool quickly. Intrusive rocks cool slowly and they’re inside the earth which acts a little bit like an oven which slows the rate of cool.
Extrusive rocks may have really small crystals smaller than one millimeter or no crystals at all sometimes. They may either be vesicular which means that rock may have air bubbles.
Intrusive rocks have crystals larger than 1 millimeter. Extrusive rocks have a very fine texture some like obsidian may even be smooth. Intrusive rocks have a coarse texture which can be described as rough because intrusive rocks have larger crystals which makes their texture.
When extrusive igneous cools really quickly rock looks glassy like obsidian. Other examples of igneous rocks are gabbro, Diorite, and peridot. Igneous rocks are very hard rocks. harder than sedimentary rocks.
Some Igneous rocks are light and some are dark. You will even find many igneous rocks in middle shades. Depending on the makeup of the magma, the color of igneous rocks may vary.
Extrusive igneous is often used to construct buildings and statues while intrusive igneous is commonly used to make gravestones and countertops because they are so durable.
Read: How do rocks move
Igneous rocks are broken down by weathering or erosion and then compacted and cemented with sediments like sand, clay, or other bits of rock. These new rocks that form have a layered appearance and are not as strong as igneous rocks.
For more information about types of rocks, you can read types of rocks
Sedimentary rocks
Now let’s take a look at sedimentary rocks. They make up around 75% of the rocks on the Earth’s surface. Pre-existing rocks are broken down. This may occur by freezing and falling of water inside the cracks of rocks, trees, and other plants growing into cracks and even blowing winds.
Next, you have erosion which occurs when these clasps or pieces of rocks are created during weathering and then are transported by wind. When the particles are deposited as loose sediment usually this is near a body of water but not always over time.
Compaction occurs as layers of deposition build on top of one another and begins to squeeze together. Cementation occurs eventually when the minerals in the water will act like glue and cement all the pieces together. The end result is sedimentary rock.
The Conglomerate can be an example of sedimentary rock. It is made up of rounded pebbles and is cemented together. Sand is cemented together to make a Sandstone. Claystone is made up of clay. Mudstone is made of mud. limestone, no it’s not made with limes but with calcite shell fragments.
Chalk is also made with calcite shell fragments. but much finer. And finally, coal is made of plant fragments. There are many uses for sedimentary rock.
For example, limestone is used to make cement. Sandstone for building stone and coal is used in generating electricity and liquid fuel. Okay, let’s leave no stone unturned. Let’s continue with metamorphic rocks.
Metamorphic rocks
Sedimentary rocks or igneous rocks are metamorphic rocks that are resulted from heat and pressure like amphibolite and Eclogite. So more common examples of metamorphic rocks are marble which has changed from limestone and dolomite.
Quartzite is a really coarse rock morphed from sandstone. Slate and phyllite are both fine-grained rocks. Phyllite is morphed from slate whereas a slate is made from shale mudstone and siltstone.
let’s take a look at metamorphic rocks. Marble rocks are classified by how they are formed. Metamorphic rocks come from existing rocks that are subjected to extreme heat and pressure.
Two major types of metamorphic rocks are foliated rocks which have layers or bands and non-foliated rocks which do not have these layers or bands. An example of sandstone when exposed to heat or pressure morphs into quartzite and limestone will morph into marble.
Schist is a coarse-grained rock changed from phyllite. Gneiss is a medium-grained rock made from schist granite and other volcanic rocks. Metamorphic rocks are used for building materials in the artwork.
Beautiful statues and vases are often made of marble. So now you are officially a rock star. You can now identify so many types of rocks. So you can now classify rocks that you find around your neighborhood. Start by picking rocks you find at the park, at the beach, or by a river.