About Stone

About Stone

There are a wide range of stone types in available, stone is thought of as a hard durable material and usually is but depending on its geological past can have widely varying properties. Stone we supply falls into three categories:

Sedimentary rock such as limestone and sandstone.

Metamorphic rock such as marble and slate.

Igneous rock such as granite.

Of the three generally sedimentary rock is the softest and absorbs most moisture and igneous rock is the hardest and least absorbent. Even though granite is a very hard igneous rock even that should be sealed because it can absorb liquid and hence stain.

Sedimentary rock

Sedimentary rock is due to sediments being laid down over time it is formed in four main ways—by the deposition of the weathered remains of other rocks; by the accumulation and the consolidation of sediments; by the deposition of the results of biogenic activity i.e. shells and skeletons of animals; and by precipitation from solution. Sedimentary rocks include common types such as chalk, limestone, sandstone and clay. Sedimentary rocks cover 75% of the Earth's surface.

Formation of Sedimentary rock

Sedimentary rocks are formed from overburden pressure as particles of sediment are deposited from the air, ice or water where the particles were carried in suspension. As the sediment deposits build up the overburden or lithostatic pressure squeezes the sediment into layered solids in the rock formation process known as lithification.

Sedimentary rocks are laid down in layers called beds or strata. Each new layer is laid down horizontally over older ones. There are usually some gaps in the sequence called unconformities. These represent periods in which no new sediments were being laid down, or when earlier sedimentary layers were raised above sea level and eroded away.

Sedimentary rocks contain important information about their history. They contain fossils of ancient plants and animals. The composition of sediments provides us with clues as to the original rock. Differences between successive layers indicate changes to the environment which have occurred over time. Sedimentary rocks can contain fossils because, unlike most igneous and metamorphic rocks, they form at temperatures and pressures that do not destroy fossil remnants.

Metamorphic rock

Metamorphic rock is the result of the transformation of a pre-existing rock type, in a process called metamorphism, which means "change in form". The original rock called the protolith is subjected to heat and extreme pressure causing profound physical and/or chemical change. The protolith may be sedimentary or igneous rock or another older metamorphic rock.

Metamorphic rocks make up a large part of the Earth’s crust and are classified by texture and by chemical and mineral makeup. They are formed deep beneath the Earth's surface by great stresses from rocks above and high pressures and temperatures. They are also formed by the intrusion of molten rock, magma, into solid rock and form particularly at the place of contact between the magma and solid rock where the temperatures are high.

Metamorphic rocks are exposed on the Earths surface by erosion and uplift bringing rock formed deep below the surface to the surface. Some examples of metamorphic rocks are slate and marble.

Igneous rock

Igneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as as intrusive rocks or on the surface as extrusive (volcanic) rocks. This magma can be derived from partial melts of pre-existing rocks in either the Earth’s mantle or crust. Typically, the melting is caused by one or more of the following processes -- an increase in temperature, a decrease in pressure, or a change in composition. Over 700 types of igneous rocks have been described, most of them formed beneath the surface of the Earth's crust. The word "igneous" is derived from the Latin igneus, meaning "of fire". An example of an Igneous rock is Granite.