Rocks are naturally formed,non-living materials made from collections of mineral grains bound together in a stable, firm mass. The presence of different mineral grains causes a difference in color and texture.
The mineral grains forming a rock can be tiny and microscopic or as big as a fingernail, depending on the rock type. Different rocks have different textures and a distinctive set of mineral composition. Rocks can be easily identified based on their mineral composition.
- How Many Types of Rocks Are There?
- Rock Facts for Kids
- The Rock Cycle
- The Three Types of Rocks
- Igneous Rocks
- Metamorphic Rocks
- Sedimentary Rocks
- Space Rocks
How Many Types of Rocks Are There?
Rocks are naturally occurring mineral composed constituting the basic unit of the solid earth’s composition and form. Rocks are classifiable into three main groups depending on their mode of formation. They can be studied in hard samples in outcrop, at their original location, or moved from their original location.
Rocks are commonly classified into igneous rock, sedimentary rocks, and metamorphic rocks, depending on the process that contributed to their formation. Igneous rocks are made of a solidified molten material known as magma, while sedimentary rocks consist of fragments extracted from precipitated material or pre-existing rocks.
Metamorphic rocks are derived from either sedimentary or igneous rocks under such conditions that result in changes in texture, internal structure, and mineral composition.
The three classifications of rocks are further subdivided into various groups, and types are based on chemical textural and mineralogical attributes. Rocks come in different sizes, and the earth’s crust and surface keep evolving through a process known as the rock cycle, which is responsible for the formation of most rocks.
Most rocks are formed using minerals consisting of oxygen and silicon, which are the most abundant elements found in the earth’s crust.
Rock Facts for Kids
- The study of rocks is called geology, and there are three different types of rocks known today.
- Rocks are made from mineral composition and have been used for millions of years for different purposes.
- Minerals making rocks are made from a composition of elements joined together in different ways, e.g., silver.
- Rocks from space are called meteorites, and scientists use them to study the solar system.
- It takes millions of years for rocks to change from one form to another through the rock cycle.
- Rocks made from minerals compose of such essential elements as silver and gold are called ores.
The Rock Cycle
It’s possible for a rock to begin as one type then change later as many times through a rock cycle process. The changes occurring during this process are slow and difficult to see, and such things as pressure and heat can cause them.
Facts for Kids
Facts for Kids
It takes thousands of years for rocks to weather and be a move by erosion. Weathering is a process that breaks down rocks into smaller pieces as a result of rain, wind, chemicals, ice, plant roots, freezing, throwing, and running water.
The Three Types of Rocks
The word igneous is derived from a Latin word meaning fire. Igneous rocks are formed when magma cools and hardens. Magma refers to the molten rock deep in the earth, and it’s the heart of igneous rocks.
Magma is composed of a mixture of gases, some volatile elements, and molten or semi-molten rocks. These rocks solidify from magma, and they are formed at high temperatures when their constituent materials crystallize from molten material. Ingenious rocks originate from processes at depths of the earth, usually in the upper mantle or the mid to lower crust.
Igneous rocks are further classified into two subcategories; extrusive and intrusive igneous rocks, depending on their formation. When igneous rocks are formed inside the earth, they are known as igneous intrusive or plutonic rocks.
Some common examples of intrusive igneous rocks are diorite and granite. These rocks have large mineral grains and a very coarse texture, which is an indication that they spent millions of years inside the earth cooling down. This time course is what causes the formation and growth of large mineral crystals.
When these rocks are formed outside or on the crust of the earth, they are called volcanic or extrusive igneous rocks. Some examples of extrusive igneous rocks are pumice, a rock with a vesicular texture. Extrusive igneous rocks get their texture when the magma ejected contains gases. When this magma cools, the gas bubbles end up trapped, which is what gives these rocks a bubbly texture.
Despite all igneous rocks forming from magma, not all magma is, made of similar composition. Different magma varies in quantities of gas, temperature, chemical compositions, and they include an incredible variety of rocks.
There are more than 700 types of igneous rocks, which are basically the heaviest and hardest of all rocks, with the exception of volcanic rocks. Other common types of igneous rocks are basalt, peridotite, andesite, tuff, gabbro, scoria, and obsidian, among others.
Just as the name suggests, metamorphic rocks are formed as a result of a metamorphosis, meaning that they changed from sedimentary or igneous rocks or even metamorphic. Metamorphic rocks go through a transformation by either pressure, heat, or both through such processes as mountain building.
There are two types of changes that lead to the formation of these rocks; dynamic and thermal metamorphism. Metamorphic rocks form as a result of changes in pre-existing rocks and from processes deep within the earth using recrystallization.
When contact metamorphism or thermal metamorphism occurs, the stones that are close to the magma start to melt partially, and their properties are altered. This results in chemical reactions, recrystallization, and fusing of crystals, as long as the temperature is the primary influence.
Dynamic or regional metamorphic changes; on the other hand, happens when rocks found deep underground are exposed to immense pressure. This pressure is significant enough to cause elongation of the stones, which ruins these rocks’ original and physical features.
Metamorphic rocks contain minerals and crystals derived from the initial rocks and some from the new minerals. There are some minerals such as garnet, kyanite, chlorite, which are clear indications of metamorphosis.
Specific significant changes in the chemical environment also result in metamorphic processes like chemical recrystallization and mechanical dislocation. Metamorphic rocks can be further classified into foliated and non-foliated metamorphic rocks.
Foliated metamorphic rocks have a precise preferential alignment as a result of the pressure squeezing and elongating the crystals. Non-foliated metamorphic rocks have no preferential alignment, with such stones as marble being composed of minerals that don’t elongate, regardless of their stress.
Metamorphic rocks are formed in different conditions, pressures, and temperatures. These rocks are buried deep in the earth’s surface and allow for metamorphosis to occur for a long time. These rocks form from tectonic processes like continental collisions, which result in friction, horizontal pressure, and distortion.
Metamorphic rocks also form when rocks are heated up by magma intrusion from the interior of the earth. Rocks resulting from metamorphic processes usually have ribbon-like layers, and sometimes their crystals are shiny. The most known metamorphic rocks are marble, slate, gneiss, quartzite, eclogite, phyllite, hornfels, and serpentinite.
Sedimentary rocks form by compacting and cementing sediments of sand, clay, silt, or rock-like gravel together. The rocks derive their name from their sediment nature. Sediment refers to a naturally occurring material that has been broken down by erosion and weathering and is transported naturally.
The sediments can be formed from the erosion and weathering of pre-existing rocks, and these sedimentary rocks have some chemical residues as well. Sedimentary rocks have a variety of defining qualities, but they all form through the deposition of materials on the earth’s surface and within water bodies.
The chemical makeup, inorganic/ organic material, and the sedimentation process behind the formation of sedimentary rocks are imperative in the classification of these rocks. Sedimentary rocks are formed after years and years of sediments compacting together and hardening.
Usually, small pieces of rocks and minerals sediments are carried by a river or stream and deposited to a larger water body where the pieces settle at the bottom. With time, these pieces compact and form solid rocks such as shale and Limestone. The most common classifications of sedimentary rocks are sandstones, biochemical rocks, conglomerates, classic sedimentary rocks, mudrocks, and chemical rocks.
Conglomerates are made of rounded gravel and angular gravel, while chemical rocks are formed through water evaporation. Mud rocks are made from solidified mud, and they are made of very fine particles.
These rocks are transported in suspended particles using a raging flow in air or water and deposit once the flow has settled. Clastic sedimentary rocks are small rock fragments that have been transported and deposited by water flow and bed flows through erosion and weathering.
Clastic sedimentary rocks are classified further depending on their composition and size of clastic crystals that make up these rocks, mostly clay, feldspar, quartz, and mica.
Biochemical rocks come from biological processes and sources. For instance, Limestone is a biochemical sedimentary rock formed from skeletons of organisms like foraminifera, corals, and mollusks.
There are other types of sedimentary rocks, such as those formed in hot springs. Some common examples of sedimentary rocks are coal, chalk, gypsum, claystone, siltstone, and dolomite. Most of the rocks found around are sedimentary, and they can take millions of years to form.
A special classification of rocks comes from space, commonly known as meteorites or space rocks. This isn’t a major classification of rocks as they are mostly composed of iron elements, and they may have different mineral makeup and elements compared to typical earth rocks.
Several processes involve information about different types of rocks, with the major ones being metamorphism, sedimentation, crystallization, and erosion. Rocks are all around us in the form of statues, tombstones, bricks, pebbles, sandpaper, and glass, among others.
Rocks have been used since the beginning of human civilization to build homes, machinery, and jewelry, among other things.
A rock is a naturally occurring solid. It is made of minerals (which are crystalline), or other mineral-like substances. The Earth's outer solid layer, the lithosphere, is made of rock. That means the Earth's crust is made of rock.How many types of rocks are there for kids? ›
There are three kinds of rock: igneous, sedimentary, and metamorphic. Igneous rocks form when molten rock (magma or lava) cools and solidifies.What are rocks very short answer? ›
A rock is a solid collection of mineral grains that grow or become cemented together. Some rocks are large while others are small. Small rocks are called pebbles. Every rock is made up of one or more minerals.What are 3 important uses of rocks? ›
Rocks and minerals are all around us! They help us to develop new technologies and are used in our everyday lives. Our use of rocks and minerals includes as building material, cosmetics, cars, roads, and appliances.What is rock made of? ›
A rock is an aggregate of one or more minerals, or a body of undifferentiated mineral matter. Common rocks include granite, basalt, limestone, and sandstone.What are 10 uses of rocks? ›
- Making Cement (Limestone) (Sedimentary Origin)
- Writing (Chalk) (Sedimentary Origin)
- Building Material (Sandstone) (Sedimentary Origin)
- Bath Scrub (Pumice) (Igneous Origin)
- Kerb Stone (Granite) (Igneous Origin)
Through the process of erosion, these fragments are removed from their source and transported by wind, water, ice, or biological activity to a new location. Once the sediment settles somewhere, and enough of it collects, the lowest layers become compacted so tightly that they form solid rock.How are rocks named? ›
Origin of Names for Rocks and Minerals. The Rock and Mineral names can be traced quite often to Greek and to Latin. It is common practice to add an “ite” to a mineral name. The suffix “ite” is derived from the Greek word lithos (from its adjectival form -ites), meaning rock or stone.How rock is formed for kids? ›
Gravity causes sediment to settle to the bottom of a body of water. These sediments gradually accumulate, forming layers that compact the layers of sediments below. Water that surrounds the sediment contains dissolved minerals that recrystallize and cement the grains of the sediment together, forming rock.What is the most common type of rock? ›
Sedimentary rocks are the most common rocks exposed on Earth's surface but are only a minor constituent of the entire crust, which is dominated by igneous and metamorphic rocks.
Glacier ice is actually a mono-mineralic rock (a rock made of only one mineral, like limestone which is composed of the mineral calcite). The mineral ice is the crystalline form of water (H2O). Most glacier ice forms through the metamorphism of tens of thousands of individual snowflakes into crystals of glacier ice.Do stones grow in size? ›
Rocks also grow bigger, heavier and stronger, but it takes a rock thousands or even millions of years to change. A rock called travertine grows at springs where water flows from underground onto the surface.What defines a rock? ›
A rock is a solid mass of geological materials. Geological materials include individual mineral crystals, inorganic non-mineral solids like glass, pieces broken from other rocks, and even fossils.What is the youngest rock? ›
So recently formed igneous rock is the youngest form of rock in most circumstances. Another major classification of rock, sedimentary rock, also forms from older rock and is younger as a result.How long has rock been on Earth? ›
The oldest dated rocks formed on Earth, as an aggregate of minerals that have not been subsequently broken down by erosion or melted, are more than 4 billion years old, formed during the Hadean Eon of Earth's geological history.How long does a rock last? ›
Rocks never die, they just change form. So they don't have a lifespan. Rocks are always changing form, but too slowly to notice with you're eyes. In fact; rocks aren't even classified as living things.How do rocks get their color? ›
The atomic bonds within a mineral generally determine which wavelengths of light will be absorbed and which will be reflected. Those wavelengths that are reflected back to our eyes determine the color of the mineral.Is coal a rock? ›
Coal is a black or brownish-black sedimentary rock that can be burned for fuel and used to generate electricity. It is composed mostly of carbon and hydrocarbons, which contain energy that can be released through combustion (burning).Do rocks contain water? ›
There are two ways that water can be included in rock. It can exist as a solid, liquid or gas trapped in pore spaces (holes) in the rock. Water molecules can also be trapped and included as part of the crystal structure of the rock.How many rocks are earth? ›
About 65% of the Earth's crust by volume consists of igneous rocks. Of these, 66% are basalt and gabbro, 16% are granite, and 17% granodiorite and diorite. Only 0.6% are syenite and 0.3% are ultramafic. The oceanic crust is 99% basalt, which is an igneous rock of mafic composition.
Chemical sedimentary rocks can be found in many places, from the ocean to deserts to caves. For instance, most limestone forms at the bottom of the ocean from the precipitation of calcium carbonate and the remains of marine animals with shells.Is salt a rock? ›
Salt, also known as table salt, or rock salt, is a crystalline mineral that is composed primarily of sodium chloride (NaCl), a chemical compound. Salt for human consumption is produced in different forms: unrefined salt (such as sea salt), refined salt (table salt), and iodized salt.Is gold a rock? ›
Gold is a valuable, yellow metal.Is chalk a rock? ›
Chalk is a soft, white, porous, sedimentary carbonate rock, a form of limestone composed of the mineral calcite. Calcite is an ionic salt called calcium carbonate or CaCO3.Why do rocks exist? ›
As strange as it sounds, rocks are made from stardust; dust blasted out and made from exploding stars. In fact, our corner of space has many rocks floating around in it. From really fine dust, to pebbles, boulders and house-sized rocks that can burn up in the night sky to make meteors or “shooting stars”.How did rocks get on earth? ›
Lava and plates
Large chunks the size of continents (called “plates”) jostle each other and this can cause earthquakes. Some of them get forced under other plates and heat up and eventually melt. This forms more lava. The lava erupts from volcanoes, then cools and forms new rocks.
Rocks don't burn. Also, metals don't burn.Who discovered rocks? ›
|The Geologist - Carl Spitzweg, circa 1860|
|Activity sectors||Government Mining Petroleum industry Engineering|
Solids can be hard like a rock, soft like fur, a big rock like an asteroid, or small rocks like grains of sand. The key is that solids hold their shape and they don't flow like a liquid.What rock is not a mineral? ›
A few types of rocks are made from materials that are not minerals. For example, coal is organic so it is not a mineral, nor is it made of minerals. Yet coal is a rock.
However, not all the rocks are hard. Soft rocks do exist. For example, soapstone is a type of soft rock. It can be easily scratched by your fingernail, and has been used to make ornamental and practical objects for thousands of years, including sculptures, bowls, countertops, etc.How do rocks change? ›
The three processes that change one rock to another are crystallization, metamorphism, and erosion and sedimentation. Any rock can transform into any other rock by passing through one or more of these processes.What is the smallest rock in the world? ›
When minerals break down (weather), they produce small particles – sand, silt, or, smallest still, clay. Clay is made up of particles less the 2 micron. or 0.002 mm, which are even smaller than sand and silt.Is diamond a rock? ›
By definition, a rock is a substance made up of two or more minerals. Although they are composed of unique minerals, rocks are what we often see in nature. A rock must have at least two minerals in its composition. Diamond cannot be considered as such because it solely includes carbon.What type of rock is rare? ›
In 2005, The Guinness Book of World Records called painite the world's rarest gemstone mineral. First discovered in Myanmar by British mineralogist Arthur C. D. Pain in the 1950s, for decades there were only two known crystals of the hexagonal mineral on Earth; by 2005, there were still fewer than 25 known specimens.Is water stronger than rock? ›
Water is not stronger than rock for its density. It's stronger than rock for its fluidity; it's dripping and flowing and flooding. It's willingness to evaporate. And, of course, it's willingness to seep into a small crack, slow down, and then expand.What type of rock is snow? ›
Because the ice changes from one solid form (snowflakes) to another (ice crystals), it is considered metamorphic rock.Can rocks move? ›
Many of the largest rocks have left behind trails as long as 1,500 feet, suggesting that they've moved a long way indeed from their original location. Rocks with a rough-bottomed surface leave straight tracks, while smooth-bottomed rocks tend to wander.Do rocks use energy? ›
Answer and Explanation: The rocks have heat energy when they get exposed to the sunlight. The rocks have potential energy, when they are under effect of gravitational energy. The rocks have energy, as they contain minerals in the form of mica, olivine, quartz, and calcite.Why are rocks heavy? ›
Rocks are heavy because they are very dense when compared to most other common materials. With an average density of 2.7 g/cm3, they are much denser than wood (~. 6 g/cm3) or water (1 g/cm3).
In nature, glasses are formed when sand and/or rocks, often high in silica, are heated to high temperatures and then cooled rapidly. The Glass in Nature display shows specimens of glass made in nature. Obsidian or volcanic glass, for example, is molten rock that has quickly cooled, becoming rock in a glassy state.Is rock a sand? ›
Sand forms when rocks break down from weathering and eroding over thousands and even millions of years. Rocks take time to decompose, especially quartz (silica) and feldspar. Often starting thousands of miles from the ocean, rocks slowly travel down rivers and streams, constantly breaking down along the way.Is the Earth a rock? ›
Our home planet Earth is a rocky, terrestrial planet. It has a solid and active surface with mountains, valleys, canyons, plains and so much more.What are 5 characteristics of a rock? ›
Physical Characteristics of Rocks - Cleavage, Streak, Hardness, Fracture, Luster.What is the oldest rock? ›
- Bedrock along the northeast coast of Hudson Bay, Canada, has the oldest rock on Earth. ...
- Earth's oldest known rock is composed of the mineral amphibole, which contains abundant garnet, seen as large round "spots" in the rock.
rock formed by the cooling of magma or lava. plutonic rock; formed from magma forced into older rocks at depths within the Earth's crust, which then slowly solidifies below the Earth's surface. rock that has transformed its chemical qualities from igneous or sedimentary.What is a rocks made of? ›
Rocks are made up of minerals. They can be all one kind of mineral, for example sandstone which is made of sand or they can made of many different types of minerals like granite. Rocks form the Earth's crust and include the surface forms we see every day.What are the 7 properties of rocks? ›
Properties that help geologists identify a mineral in a rock are: color, hardness, luster, crystal forms, density, and cleavage.What is the smallest rock on Earth? ›
When minerals break down (weather), they produce small particles – sand, silt, or, smallest still, clay. Clay is made up of particles less the 2 micron. or 0.002 mm, which are even smaller than sand and silt.What is the hardest rock? ›
Since all minerals are also rocks, diamond is the hardest rock.
Technically, ALL rocks start as magma. The magma (molten rock under the surface) and lava (molten rock on the surface) hardens into igneous rock. The igneous rock then breaks apart over time through the process of weathering.Are all rocks natural? ›
Rocks are natural material made of grains of one or more minerals. A mineral is a natural compound that usually exists in rocks as crystals. Geologists classify rocks into three groups according to how they were formed: igneous, sedimentary and metamorphic. We use rocks from each group as natural resources.