Kyneton Dry Stone Walling
stone
Geology
There are three main types of stone used in masonry construction.
The differences between them are how they were formed.
Sedimentary
Metamorphic
Igneous
Sedimentary
Sedimentary rocks are types of rock that are formed by the accumulation or deposition of small particles and subsequent cementation of mineral or organic particles on the floor of oceans or other bodies of water at the Earth's surface. Sedimentation is the collective name for processes that cause these particles to settle in place. The particles that form a sedimentary rock are called sediment and may be composed of geological detritus (minerals) or biological detritus (organic matter). Before being deposited, the geological detritus was formed by weathering and erosion from the source area, and then transported to the place of deposition by water, wind, ice, mass movement or glaciers which are called agents of denudation. Biological detritus was formed by bodies and parts (mainly shells) of dead aquatic organisms, as well as their fecal mass, suspended in water and slowly piling up on the floor of water bodies (marine snow). Sedimentation may also occur as dissolved minerals precipitate from water solution.
Sedimentary rocks are only a thin veneer over a crust consisting mainly of igneous and metamorphic rocks. Sedimentary rocks are deposited in layers as strata, forming a structure called bedding.
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Examples of sedimentary rocks:
Sandstone
Conglomerate
Limestone
Shale
Metamorphic
Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means "change in form". The original rock (protolith) is subjected to heat (temperatures greater than 150 to 200°C) and pressure (100 megapascals (1,000 bar) or more), causing profound physical or chemical change. The protolith may be sedimentary, igneous, or existing metamorphic rock.
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Metamorphic rocks make up a large part of the Earth's crust. They may be formed simply by being deep beneath the Earth's surface, subjected to high temperatures and the great pressure of the rock layers above it. They can form from tectonic processes such as continental collisions, which cause horizontal pressure, friction and distortion. They are also formed when rock is heated by the intrusion of hot molten rock called magma from the Earth's interior. The study of metamorphic rocks (now exposed at the Earth's surface following erosion and uplift) provides information about the temperatures and pressures that occur at great depths within the Earth's crust.
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Some examples of metamorphic rocks are gneiss, slate, marble, schist, and quartzite.
Gneiss
Marble
Schist
Quartzite
Igneous
Igneous rock (derived from the Latin word ignis meaning fire), or magmatic rock, is formed through the cooling and solidification of magma or lava. The magma can be derived from partial melts of existing rocks in either a planet's mantle or crust. Typically, the melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition. Solidification into rock occurs either below the surface as intrusive rocks or on the surface as extrusive rocks.
Some examples of igneous rocks are Basalt, Granite and Pumice.
Basalt
Agglomerate
Granite
Pumice