In this blog post, you’ll learn about the different types and characteristics of impermeable rocks.
Impermeable Rocks Examples (Characteristics and Types)
What are Impermeable Rocks?
The Earth’s crust consists of many different types of rocks and sediments.
To figure out the kind of rock one is, geologists will categorize rocks into different groups and subgroups.
Two of these groups of rocks are permeable and impermeable.
Permeable rocks have holes or empty spaces within them that allow water to flow through them.
Examples of permeable rocks include sandstone, karst limestone, fracture igneous, and metamorphic rocks.
A rock that is impermeable does not permit water or any other fluid to pass through it.
Consider the effect of pouring water on a concrete surface.
Water can soak into concrete, but it is more likely to run off the surface than soak into it.
Similar characteristics apply to impermeable rocks.
Another example is shales, as well as unfractured igneous and metamorphic rocks.
These rocks do not allow water to pass through their grains because they are so closely packed.
What Are The Physical Characteristics of Impermeable Rocks?
The metamorphic rock slate is created when shale or mudstone undergoes low-grade metamorphism.
Slate is very fine-grained, and its crystals are not visible to the naked eye.
Clay is the main component of slate, but the clay can change into mica under extreme pressure.
Marble is a rock formed by the metamorphosis of limestone or dolomite.
This mineral is composed of fragments of calcite or dolomite interlocked with each other.
As limestone undergoes metamorphism and is exposed to high temperatures and pressure, marble is formed.
Metamorphism is characterized by new crystals growing and an interlocking calcite matrix.
For limestone to metamorphose, it needs marble, extra iron, and graphite.
The color of the calcite matrix changes with the duration of the impurity function.
On Earth’s continental crust, granite is the most common type of intrusive rock.
A silica-rich magma thousand of kilometers beneath Earth’s crust crystallizes granite.
The hydrothermal solutions released by such granite bodies form many mineral deposits near crystallizing granite bodies.
Often, granite is found in large bulks due to its location.
The Earth’s crust has deeply eroded in these areas, resulting in large plutons on the continents.
Due to the large mineral grains that granite produces are the result of very slow solidification at deep-buried locations.
The texture of granite is phaneritic, which means it is medium to coarse grained.
In some places of the stone, it is porphyric.
There are several varieties of mudstone that differ in their grain size, but all of them are sedimentary rocks.
Some rocks that are considered mudstone include claystone and siltstone.
It is smooth to touch, and the grains are very fine.
The rock can be soft but hard enough not to break when picked up from the ground.
You can tell mudstone is not shale due to how blocky it breaks when chipping apart.
The Common Appearance of Impermeable Rocks
Slate is often seen in a variety of colors.
Some of the colors you can discover in slate include red, brown, black, blue, green, and beige.
Usually, marble only comes in two colors which are white and pink.
The grained size of a marble is medium and can be seen without a microscope.
Granite often appears in white, gray, black, and mottled pink colors.
However, the most common color of granite is gray and black, which is why people associate with a salt-and-pepper color.
Mudstone often comes in the color of brown, red, black, and white.
It can also be seen in the shade of blue or green.
The Chemical Composition of Impermeable Rocks
The slate chemical composition includes the minerals muscovite, quartz, pyrite, chlorite, and hematite.
In addition, the rock may also contain small amounts of graphite, magnetite, feldspar, tourmaline, and zircon.
Some of the pink slates of North Wales display a soft green textured surface, due to ferrous discount spheres forming around the iron nuclei.
Sometimes these spheres are deformed by applying pressure to them, converting them to ovoids, that when viewed from the specimen’s cleavage plane, appear as ellipses.
Marble is mainly made out of calcium carbonate or CaCo3.
It also contains smaller amounts of silica, iron oxide, magnesium carbonate, and aluminum oxide.
Granite’s chemical composition consists of silica, aluminum oxide, CaO, K2O, FeO, and FE203.
The mineral will always consist of feldspar and quartz.
Granite’s light colors are generally derived from quartz and feldspar, ranging from pinkish to white.
Those darker accessory minerals contrast with the light background color.
Therefore, classic granite looks like salt and pepper in appearance.
Mudstone’s chemical composition includes aluminum oxide, iron oxide, clay minerals, and silicon dioxide.
It also has the chemical composition of NaCI and CaO.
Depending on how humid the climate is, it may contain kaolinites or illites compounds.
Where Can You Find Impermeable Rocks?
Slate can be found all over the world.
In the European countries, slate is located in Spain, France, Italy, and Portugal.
In North and South America, slate can be found in Brazil, New York, Pennsylvania, Virginia, Vermont, and Maine.
Slate is also found in Australia, the Arctic, and China.
Marble is another rock that can be found all over the world.
In the European countries, marble can be found in Russia, Italy, Spain, Greece, Germany, Sweden, and Romania.
In the United States, you can find marble in Alabama and Texas.
You can also find the mineral in China and India.
Granite can be found worldwide.
Some of the granite is located in South Africa, China, Finland, North America, and India.
In North America, you can find mudstone in the US, Brazil, Peru, and Bolivia.
The stone can also be found in China, South Africa, Australia, India, Bangladesh, and Scotland.
Impermeable rocks do not allow water or fluid to flow in between the cracks of them.
Examples of impermeable rocks include slate, marble, granite, and mudstone.
Remember, mudstone breaks down into shale, claystone, and siltstone.