Nature and types of stone
Natural stone is classified based on its origin millions of years ago. There are three basic types of stones:
- Volcanic or Igneous - formed on solidification of lava or magma.
- Sedimentary - formed due to erosion and deposition of material through natural forces.
- Metamorphic - formed by modifications in existing rocks due to extreme pressure and heat
Limestone:
- Calciferous minerals were deposited in layers on ancient river and ocean beds.
- These layers hardened over the years due to high pressure, giving rise to soft limestone with colours from cream to gray and blue.
- It does not polish to a gloss.
- It is porous and liable to stains and scratches.
Marble:
- Marble is the result of metamorphosis of limestone due to immense heat and pressure.
- It is harder and less porous than limestone.
- It takes on a good shine.
- It ranges in colour from pure white to pitch black to exotic colours like brilliant green, bright red and creamy yellow.
Granite:
- Granite is formed by the gradual cooling and solidification of magma inside the earth's crust under high pressure.
- Minerals crystallize slowly to give granite its characteristic crystalline structure.
- It comes in many varieties of colours and patterns.
- It is available to fabricators in large slabs averaging 5’ x 6’. The slabs are polished to a high gloss on one side.
- As a stone is a natural product, no two pieces are exactly the same, even if they mined from the same quarry.
- Each slab is unique, no top can be replicated exactly.
Travertine:
- Travertine is formed through accumulation of calcite from hot springs, often classified as limestone and marble.
- It is usually cream or rufescent.
- It has holes due to water flowing through the stone. These holes are often filled with synthetic resin or cement.
- Maintenance is required if the holes are not filled.
Onyx:
- The name comes from the Greek word onyx, which means fingernail.
- Onyx is classified under chalcedony quartz mined in Brazil, India, California and Uruguay.
- It has a fine texture and is black in colour. However, it displays white bands or ribbons against a black or brown background.
- It is formed in caves as stalactites and stalagmites by the slow precipitation of cold, mineral-rich water.
- Onyx was very popular with the ancient Greeks and Romans.
Slate:
- Slate is a fine-grained metamorphic stone formed from clay, shale, and sometimes quartz.
- It has a thin texture and breaks easily.
- It is often split and comes in various sizes or shapes.
- It can be separated into flat sheets.
- It is uniform in colour, available in shades such as dark to light green, mottled purple, black, gray or dark red.
- Slate is characterized by a distinct cleft pattern, unless polished smooth.
Tiles:
- Tiles are man made, first produced 7000-8000 years ago.
- Glazed decorative tiles were first produced in Egypt. The art then spread to Persia and across North Africa.
- Spanish conquistadors popularized tiles across the world. They were used to decorate churches of newly built missions.
- Initially, tiles were too expensive for utilitarian purposes in the colonies, found almost exclusively in the homes of the wealthy.
- Today glazed tiles, commonly called ceramic tiles, are used in an almost infinite number of ways throughout the world.
