The classifications for rock and stone are: Igneous, Sedimentary and Metamorphic rocks.
All of them differ in appearance and mineral characteristics.
Liquid magma cools and solidifies underneath or on top of the earth’s crust.
There are three Igneous Rock types: Extrusive, Intrusive and Minor Intrusive.
Created by magma crystallizing on or just under the Earth's surface. A fine-grained texture because it cools rapidly. (If rock cools slowly, larger crystals grow).
Basalt (Lava Stone) is the most prevalent Extrusive Rock.
This Magma cools down whilst under great pressure, deep within the earth and cools it over a longer period of time. Intrusive rock has a coarse grain, with visibly larger crystals. Erosion of the overlying rock exposes it at the surface.
Granite is the most common name for an intrusive rock.
Formed from a wide variety of eroded rock sediments including, mud layers, sand grains, residue of seashells, plants and animals. Eroded by weathering, transported through water and wind and the sediments are deposited and build up strata layers. The sediment becomes compacted and cemented together over time, forming hard rock.
Depending on the origin of the sediments, Sedimentary Rock is divided into the following:
is an organic rock, created by the natural cementing of water bodies, with organisms, like coral, plants and sea shells.
is a sedimentary rock, created by the cementing of eroded grains of igneous sand rock and small mineral fragments
Can be formed from igneous, sedimentary and even metamorphosed, metamorphic rock (which is altered by extreme heat and/or pressure)
Mineralogical and textural changes are caused by a chemical alteration of the stone's elements. These change the characteristics of the original rock type and this process creates the following different examples of metamorphosed rock:
Created by heat and pressure from sandstone, originally a sedimentary rock
Created by heat and pressure from limestone, originally a sedimentary stone
Created by heat and pressure on finely ground rock mud sediment, originally sedimentary mudstone and shale, which has been washed out to sea and laid down
Created from many different source rocks, through heat and pressure and include;
Slate, which was originally metamorphic and has been continually metamorphosed and re-crystallised into Gneiss.
Granite, which was originally Igneous
Sandstone, which was originally sedimentary