SANDSTONE and QUARTZITE
Sandstone
The term sandstone refers to the sand sized (0.06 to 2.0mm) clasts that are cemented together by other agents. Therefore, sandstone could be of any mineralogy, but the overwhelming majority of them on the market are quartz-based.
The durability and performance of this stone is not as greatly influenced by the sand sized particles, as it is influenced by the cementing agents that binds these particles together.
Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, it may be any color, but the most common colors are tan, brown, yellow, red, gray, pink, and white. Since sandstone beds often form highly visible cliffs and other topographic features, certain colors of sandstone have been strongly identified with certain regions.
Rock formations that are primarily composed of this rock usually allow percolation of water and other fluids and are porous enough to store large quantities, making them valuable aquifers and petroleum reservoirs. Fine-grained aquifers, such as sandstones, are more apt to filter out pollutants from the surface than are rocks with cracks and crevices, such as limestone or other rocks fractured by seismic activity.
This natural stone is mined by quarrying. It is sometimes found where there used to be small sea areas. It is usually formed in deserts or dry places like the Sahara Desert in Africa, the Arabian desert in the Middle East and the Australian desert. In the western United States and in central Australia, most sandstone is red.
Many types of this rock are used in cubic sections as sills, coping, water-tables and other exterior features. Exterior cladding is also a common application, although this stone variety is typically used in thicker sections than other stone types due to lower bending strengths.
While sandstone has been used in both countertop and shower lining applications, the varieties that are suitable for these installations are limited.
Quartzite
Quartzite is a metamorphic rock that is formed from sandstone. It can be of exceptional strength, density, and hardness. The strength, abrasion resistance, and weathering durability of this rock type expand its application possibilities to include most any common uses for natural, dimension stone
Unlike sandstone, quartzite breaks through, not around, the quartz grains, producing a smooth surface instead of a rough and granular one. Quartzites are snowy white, less often pink or gray. They yield a thin and very barren soil and, because they weather slowly, tend to project as hills or mountain masses. Many prominent ridges in the Appalachian Mountains are composed of highly resistant tilted beds of natural stone.
The term quartzite implies not only a high degree of hardening (induration), or "welding," but also a high content of quartz. Most quartzites contain 90 percent or more quartz, but some contain 99 percent and are the largest and purest concentrations of silica in the Earth's crust. Pure quartzites are a source of silica for metallurgical purposes and for the manufacture of brick. This stone is also quarried for paving blocks, rip-rap, crushed stone, railroad ballast, and roofing granules
