History Over many millions of years a variety of processes within the earth’s core caused massive rock beds to develop and rise to form the earth’s crust. Three main types of rock formations were identified as Sedimentary, Metamorphic and Igneous rock. (Each type is described further on in this guide).
Around the world different cultures discovered that these rock beds were made up of thousands of varieties of beautiful, functional and long lasting building materials. The Egyptians commonly used limestone blocks to build the pyramids whilst the Greeks used marble to create ornamental statues and build temples. Michelangelo used marble in Italy to carve magnificent statues. The Romans used stone to build roads, domes and arches. Some cultures used broken stones from rivers and outcrops to build homes. Others set up quarries to mine the natural stones and used them to construct buildings and monuments.
Marble and granite were popular choices when building monuments due to their ability to take a polish and to resist weathering over thousands of years. Stones such as sandstone, slate and limestone were more likely to stain, crack and weather over periods from 50 – 100 years. Techniques were developed though to enhance the weather and stain resistance of some stones, and to improve their look and feel. Sealing of surfaces enabled the softer stones to be used in more practical applications. Polishing became a popular choice as it produced an appealing high gloss and hardwearing finish on granite and marble surfaces.
In 1822 the Mohs scale was designed by a German Frederich Mohs to evaluate the hardness of different natural stones and to determine the suitability for various projects and environments. This governed which tools were appropriate for cutting, carving and polishing, and the type of care needed to maintain the finish. The Mohs scale of measurement is still used today. Understanding the Mohs scale can assist owners of natural stone to prevent damage when maintaining their stone surfaces. Hard substances like sand grit rated at 6 will scratch softer substances like marble rated at 3. Material like granite rated at 6 is better suited to kitchen benchtops rather than marble rated at 3, which is prone to scratching. The rating is from 1 to 10:
9: Sapphires and rubies
6 – 7: Granite and manufactured stone
5 – 5.5: Opal
3 – 4.5: Serpentine
3: Marble, limestone, slate, gold, silver and copper
2: Can be scratched with a fingernail
1: Will crumble like talc
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