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Identifying Rocks

Poushali Ganguly Jan 27, 2019
If you are interested to know the characteristics of each rock and the traits that make them unique, read this post which describes the method of identification of rocks.
To identify rocks, it is necessary to understand their composition and the way they are formed. It is essential to understand that rocks are made up of minerals, so to identify rocks; minerals also have to be identified. Rocks are made up of minerals like quartz, calcite, feldspar, and micas. Most of the time rocks are made up of more than one mineral.

Steps Involved

Does the rock consist of grains and fossils?

If the rock consists of grains and fossils, then it can be classified as sedimentary rock, which is formed of rock bits and pieces. The presence of fossils can also be explained by the duration that these rocks take to form.
If the rock has rounded pebbles, which seem to be stuck together then the rock is a conglomerate rock.
If the rock seems to be made up of tiny pieces and materials then it is sandstone, which are formed as a result of the grains becoming oxidized.
Does the rock consist of colored crystals?

If the rock consists of colored crystals or crystals that you can detect, then you can classify it as igneous rock. It is formed by hot molten rock called magma which erupts onto the earth surface, below the ocean, and also inside the earth's crust.
If the igneous rock is gray, full of holes or light then it is pumice, but if the rock has a glassy texture and is black or red in color then it is the obsidian. The rock can be basalt if it is dark greenish in color, and doesn't have glassy texture.
Basalt is formed when small amount of lava comes out as thin lava. It is found in the ridges and crevices.
Is the rock made up of crystals that are separated into bands?

If the rock that you are trying to identify has distinct bands of white crystals then it can be classified as a metamorphic rock. It is formed when other rocks that are buried deep inside the earth's crust collide and break or melt due to the tectonic movements or the massive heat and pressure.
After melting, once when they again recrystallise, they might take up the other minerals that are around, and those minerals are visible in the rock as the white band of sugary crystals. The metamorphic rock can be either marble or quartzite.
Marble is formed when the source stone is under intense heat and pressure. The stone crystallizes destroying any trace of fossil present in the source stone.
These are the basic questions that would help you to determine the type of the rock. The arrangement of crystals, size of the particles, presence of holes, and the color of the holes also help in identifying rocks.