white rock formation on water

Types of Rock and Their Uses

Rocks come in all sorts of different shapes, sizes and colors – there are probably around 4,000-5,000 species worldwide and most have numerous uses.

Limestone is a sedimentary rock used for creating concrete and mortar. Additionally, Rapa Nui (Easter Island) natives used limestone to sculpt its iconic moai statues using this material.


Sedimentary Rock Sedimentary rocks make up most of Earth’s rocks, providing geologists with invaluable insights into our planet’s past environments and shaping. Their structures and mineral composition allow geologists to reconstruct past landscapes and environmental conditions through geologic time travel; economically speaking, sedimentary rocks contain many natural resources including coal, oil and gas reserves, phosphate deposits, groundwater reserves, and salt deposits that offer immense economic potential.

Sedimentary rocks form from the accumulation of weathered or eroded rock material that has become compressed and cemented together over time, eventually becoming sedimentary rocks. Their creation occurs over a continuous process taking place over many depositional environments with each environment providing its own unique set of conditions that influence what type of sedimentary rock will eventually form there.

Typically, sedimentary rocks are divided according to their predominant particle size: shale and siltstone are composed of clay-sized particles; sandstone has larger particles such as silica; conglomerate and breccia are both types of clastic sedimentary rock with large (greater than 2mm in diameter), round clasts such as pebbles or boulders surrounded by a matrix of sand or mud; these may further be divided based on mineral content or chemical composition.

Key characteristics of sedimentary rocks are their layers. Deposition occurs in beds which often differ in terms of lithology, texture and color; layers can range in thickness from centimeters to several meters thick. A sequence of such beds with distinctive characteristics forms what geologists refer to as formations: fundamental geologic map units.

Not only can sedimentary rocks display layers, but they often also exhibit additional structures. These may either be primary or secondary in origin; primary structures form during deposition and can be observed on their surfaces while secondary ones typically form after the rock has lithified but in similar environments to where its predecessor bed was laid down – these secondary features may include fissures and cracks.

Another way sedimentary rocks can be useful is in studying fossils found within them. Fossils play an integral part in geology by providing insights into the environment in which sedimentary rock formed; fossils of shellfish and plants typically indicate marine environments, while some undergo permineralization processes that change their chemical makeup while keeping their form.


Igneous rocks are formed when molten material cools and hardens into solidified deposits, such as plutonic or volcanic (extrusive) igneous rocks, creating them either underground in plutonic formations, or on the surface as volcanic (extrusive) eruptions, with coarse-grained or fine-grained textures, angular crystals that haven’t been worn down by weathering, or are exposed in other ways than sedimentary and metamorphic rock types. Igneous rocks come in various forms: underground (plutonic igneous), while volcanic (extrusive), and on surface volcanic (extrusive), creating plutonic plutonic igneous rocks for which plutonic formations may form as plutonic plutonic igneous rocks; otherwise on surface volcanic (extrusive). Igneous rock forms in either of two ways – plutonic plutonic) or over surface volcanic (extrusive) form either underground (plutonic), or surface volcanic (extrusive). Both forms feature coarse-grained or fine-grained textures with coarse graininess in common while sedimentary and metamorphic) rocks typically display more angular crystal formation than their counterparts due to not wearing or being worn down over time like sedimentary and metamorphic rock counterparts are.

Geologists classify igneous rocks based on their composition and mineral content rather than texture, with four broad classifications being felsic, intermediate, mafic, and ultramafic rocks. Felsic rocks contain high proportions of silica with low iron and magnesium content and usually appear light in color such as quartz, K feldspar or mica. Intermediate rocks consisting of proportions between silica, iron and magnesium are found between felsic and mafic rocks called diorite and andesite while mafic rocks contain high amounts of iron and magnesium content which appears dark-brown or grey in color – these types of rocks called gabbro or basalt; finally ultramafic rocks have extremely high magnesium and iron concentrations which result in dark-color coarse-grained dark colors such as black-brown or grey hued rocks called peridotite or komatiite.

Some igneous rocks can be used as construction material or decorative stones. Pumice, which floats due to gas pockets in its pores, is one such material while obsidian is a type of volcanic glass with very sharp edges that is often used as surgical instruments. You may even find examples of these rocks right in your own backyard! For an even grander experience visit national parks such as Yellowstone and Volcanoes to witness massive igneous formations first-hand.

Utah is home to numerous national parks where igneous rock can be found, such as Canyonlands and Arches national parks. Sandstone forms many of Utah’s famous cliff formations; another form of cemented igneous rock known as basalt can be used for railroad track ballast or countertops; furthermore, trap rock is another very coarse-grained form commonly used as road base material and crushed rock; additionally it can serve as aggregate in concrete and asphalt mixes.


Metamorphic rocks, also referred to as metamorphic sedimentary rocks, are those composed of initially igneous or sedimentary rock material that has undergone intense heat and pressure resulting in metamorphism – the process by which their chemical composition or mineral assemblage changes drastically, such as when blueschist is created.

Metamorphism occurs when rocks change from their original state – typically igneous and sedimentary rock – into something less similar, yet still contains some original minerals. Atoms squeeze together, and minerals recrystallize in an effort to form more compact and dense rocks. Metamorphic rocks do not generally exhibit layers or banded appearances like sedimentary rocks do, though some varieties do contain stripes and bands similar to sedimentary formations that indicate its metamorphic origins. A stripe or band in any metamorphic rock is a surefire sign that it belongs to its parent rock class!

One of the most widespread forms of metamorphic rock is quartzite. This hard, dense rock formed through metamorphism of sandstone and chert is often used in kitchen countertops, flooring, walls and roofing tiles – as well as roofing tiles and stair treads! Another popular metamorphic rock type is soapstone; an extremely dense fine-grained form which can be found worldwide and which serves both interior and exterior counter surfaces, flooring applications as well as surface material for sinks.

Other types of metamorphic rock include hornfels, amphibolite, and skarn. Hornfels is a non-foliated metamorphic rock formed from hot ingenious lava hardening parent rocks; its color may range from black, brown, reddish-brown, grayish or greenish depending on how hot the lava was when forming it; it can be black, brown, reddish-brown to grayish or greenish and extremely hard. Hornfels can be used for making floor tiles as interior finishes; making floor tiles as interior finishes; making paving stones; facing stones; and making road aggregates from such hard materials.

Amphibolite is a weakly-foliated metamorphic rock formed during regional metamorphism from mafic igneous rocks such as basalt and gabbro as well as mafic sedimentary rocks such as marl and greywacke. Amphibolite often features dark tones with minerals like hornblende, biotite, garnet mica and plagioclase as its predominant minerals.


Rocks add visual interest and texture to any outdoor space and complement other landscaping features beautifully. They’re also helpful for controlling weeds and erosion prevention – mulch is often recommended, but rocks will last longer with less maintenance required, plus they don’t attract pests like mulch might.

Decorative rock comes in many sizes and colors, from larger rocks suitable for creating dry creek beds to pea gravel-sized rocks that create natural ground covers. All decorative rocks require only low maintenance when combined with boulders, flowers or foliage in a garden setting.

Minerals are naturally-occurring inorganic substances with distinct chemical composition and physical properties. There are thousands of minerals present on Earth and each one exhibits distinct physical attributes; most common minerals come from either an igneous, sedimentary, or metamorphic source.

Although rocks serve many uses, it’s essential that we remember that nature should remain unaltered as much as possible in order to maintain the beauty and wonderment of national parks and wilderness areas. While it might be tempting to move or alter rocks encountered, this action could cause irreparable harm – instead, take time to admire their beauty while learning as much about them as possible!

Decorative rocks make an excellent addition to any landscape and come in various shapes, colors and textures. Use decorative rocks to create a rock garden, cover bare ground or hide less desirable features of your yard.