Types of Rocks and the distinct ways that they are formed

First rock, Igneous. They are formed by solidification

Magma/Lava solidifies, turning into an igneous rock.

There are two different types of Igneous rocks.

First, Intrusive, which form under the crust and from solidified magma.

Here is an example of an Intrusive Igneous rock, Granite.

Second, Extrusive, which form above the crust with solidified lava.

Here is obsidian, an extrusive igneous rock.

Now lets talk about sedimentary rocks.

Sedimentary rocks form when sediments go through Deposition, Burial, Compaction and Cemention

There are 3 different forms of sedimentary:

Clastic - formed by compaction and cementation.

Here is an example of an clastic sedimentary rock, Conglomerate.

crystalline, when minerals in water stay and the water evaporates, leaving the rock behind.

Here's rock salt, a crystalline rock. All crystalline rocks are clear.

Finally, bioclastic, which form from once living things.

This bioclastic rock is called coal.

Finally, Let's talk about metamorphic rocks.

Metamorphic rocks form when either Igneous rocks, sedimentary rocks or even other metamorphic rocks go under extreme heat and/or pressure.

Metamorphic rocks are also formed with metamorphism.
Here is the metamorphic rock known as meta-conglomerate.

These properties are useful for identification of minerals.

The first property is hardness, which is when the mineral is scratched against some glass.

If the mineral makes a scratch, than it is harder than glass.

The second property is Cleavage/Fracture.

On the left is a cleavage mineral, the one on the right is a fracture mineral.

The third property is luster, which mean if the mineral is metallic, greasy, silky or earthy.

This is pyrite, it has a metallic luster.

The fourth is color, obviously meaning the color of the mineral. This could be unreliable, since the mineral could change it's color.

The fifth property is streak. Streak uses small pieces of unglazed porcelain known as a streak plates.

The sixth and final property is texture, which refers to the relationship between the materials of which a rock is composed.


Created with images by James St. John - "Stromatolites (Chencha Formation, Ediacaran, Neoproterozoic, 580 Ma; central Siberian Craton, Russia)" • James St. John - "Granite" • kevinzim - "obsidian" • James St. John - "Conglomerate" • steinchen - "salt lamp minerals rock" • Pavlofox - "coal miners minerals" • James St. John - "Quartz-pebble metaconglomerate (Jack Hills Quartzite, Archean, 2.65 to 3.05 Ga; Jack Hills, Western Australia) 1" • 949158 - "calcite stone natural" • paleo_bear - "Pyrite"

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