Stone origins: Marble
Your glistening marble floor or countertop may well be the pride of your home. But have you ever wondered where this now-impressive centerpiece of your home got its start? The origins of marble are nearly as fascinating as the alluring veins and swirls which characterize its surface.
The basics of marble
Marble is a metamorphic rock, which means it formed from the transformation of another type of rock due to changes in pressure and temperature. Large amounts of temperature and pressure cause the minerals that the original rock is made from to lose their stability, break down and form new minerals. In the case of marble, this original rock is limestone.
Metamorphic rocks are usually known for two particular types of textures:
- Foliation, which characterizes most metamorphic rocks, and features minerals in parallel lines of foliation
- Granular, where the rock is made up of interlocking crystals of only one mineral
Marble is among the latter.
The forging of marble
Marble is formed in the fires of the constant movement of tectonic plates beneath the earth’s surface. As these plates move and converge, limestone in the earth is subject to enormous amounts of heat and pressure.
This has two effects: One is to eradicate the presence of fossils which characterizes limestone. The other is to change the chemical composition of the stone, as the calcite which forms the limestone recrystallizes and becomes denser.
In other words, think of the movements of the earth’s crust as a gigantic kiln. Just as placing wet clay in a such a furnace will eventually harden the material, the same happens to marble as it’s subjected to the incomprehensible heat and pressure beneath the earth. Limestone goes in, marble comes out.
Marble is known for its many colors and intricate patterns, which are also a result of this process. As small bits of impurities make it into the rock during the process – such as sand, silt and clay – they end up as beautiful decorations that please the eye.
Just because marble is forged in the deep fires of the earth doesn’t mean it’s indestructible, however. Various substances can stain it and alter its hard-won appearance. That’s why you always want to seal this metamorphic marvel with Dry-Treat’s STAIN-PROOF Original™.
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