Conglomerate - Rock

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Geology Conglomerate

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The conglomerate is a sedimentary rock made up of rounded pebbles and sand that is usually held together (connected) by silica, calcite, or iron oxide. Conglomerate sedimentary rock is a stone similar to sandstone but rock particles are angular gravel or rounded rather than sand. 

Conglomerate refers to coarse-grained rock that is formed in riverbeds. The pebbles and sand can be made up of many minerals, but it is generally quartz-based minerals.

The hardness of the conglomerate sedimentary rock is variable, and it often resembles concrete. It is generally found in thick, crudely, and stratified layers. Conglomerates are generally used in the construction industries as decorative stones.

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Conglomerate Composition

There can be a variety of conglomerate compositions. As a clastic sedimentary rock, it can include clasts of any rock material or weathering product that is washed downstream or down current. The rounded clasts of conglomerate can be mineral particles such as quartz, or they can be sedimentary, metamorphic, or igneous rock particles. The matrix that joins that large clast together can be a mixture of sand, mud, and chemical cement.

Conglomerate Rock Classification

The classification of conglomerate rock is based on the following factors:

  • Amount and type of the matrix present in the rock

  • Composition of the gravel-sized clasts they contain

  • Size range of gravel size clasts present 

The classification method of conglomerate rock depends on the detail and type of the research being carried out.

Conglomerate Characteristics and Properties

The main conglomerate characteristic is the presence of readily visible, rounded clasts bound within a matrix. The geology conglomerate is a sedimentary rock type that looks like concrete. It comprises large, rounded pebbles ( clasts) joined by a matrix made up of calcite, iron oxide, or silica.

The conglomerate property depends on its composition.  It can be found in any other colour and may be either hard or soft.

The conglomerate can be used as a fill material for roads and constructions. Hard rock may be cut and polished to make dimension stone.

Conglomerate Uses 

Conglomerate uses are very rare because of their non clean breakage and fine particles are reliable. It can only be used as a crush where low-performance material is required. Conglomerates can be crushed to make a fine aggregate that can be used for roads and buildings in construction industries. Conglomerates are also used in the cement manufacturing industry.

Most of the conglomerates are colourful and have attractive looks, but they are only rarely used as ornamental stone for interior use.

Conglomerate with smaller clasts size can be easily cut in the required shapes. If the conglomerate found is with good cementing material, its application as dimension stone for flooring and veneer on walls and roof tiles is possible.

Conglomerates are providing excellent material for monuments, artifacts, and sculpture formation, and in the creation of small figurines.

Conglomerate Rock Formation

Conglomerate rocks are formed by larger pieces of sediments, such as sand and pebbles. The pieces of sediments in conglomerate rocks can be very big ( like boulders) or very small ( like peas). Most conglomerate rock formation occurs in shallow water. Conglomerate rock is formed by pressure and joined together with dissolved minerals. Conglomerate rocks are used in the construction industries and as decorating stones, such as for buildings.

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Conglomerate Rock Texture

The conglomerate sedimentary rock contains at least 30% rounded to sub angular clasts larger than 2mm (0.079) in diameters such as granules, cobblers, pebbles, and boulders. However, conglomerates are rarely composed entirely of gravel size clasts.  Generally, the space between gravel sizes is filled by a mixture composed of different amounts of silt, sand, and clay known as matrix. 

If the individual gravel clasts in a conglomerate are set apart from each other by a plethora of matrices such that they are not in contact with each other and float within the matrix, it is considered a paraconglomerate. Paraconglomerate is also often not stratified and can comprise more matrices than gravel clasts. If the gravel clasts of a conglomerate come in contact with each other, then it is called an orthoconglomerate. 


Did You Know?

  • Conglomerate rock is believed to be the oldest rock on the Planet as the layers of meta conglomerate have an age of more than 4 billion years.

  • Conglomerate rock is a sedimentary rock consisting of individual clasts with a finer-grained matrix that has been cemented together.

  • Conglomerate rock differs from breccia by its rounded clast.

FAQ (Frequently Asked Questions)

1. What are the Different Colours of Conglomerate Rocks?

Ans: The colour of conglomerate rocks depends primarily on the colours of clasts and matrix. If you find uniformity, the following conglomerate rock colours are commonly found:

  • Beige

  • Black

  • Brown

  • Buff

  • Light to Dark Grey colour

  • Orange

  • Rust

  • White 

  • Yellow

2. Where are Conglomerate Rocks Found?

Ans: As we know, conglomerate rock formation occurs in areas where an adequate supply of water from different water bodies is possible. These water bodies include lakes, rivers, glaciers, and sea beaches with strong current waves. Significant deposits of conglomerate rocks are found in the areas such as Asia, Africa, Europe, North America, South America, Australia, and others.

3. Which Type of Rock is Considered a Conglomerate?

Ans: In Geology, a conglomerate is considered a clastic rock. Here, the term clastic is derived from clasts. The gravel-sized pebbles, which are more than 2 mm in diameters are termed clasts.

When the matrix is made of sand, silt, and clay particles and fills the gaps between the clasts and also joins the clast object together, then the conglomerate formation takes place.