How are gems formed on Earth?

Many bizarre and unusual conditions, the perfect temperature, composition, mineral and pressure must work together to create the beautiful gemstones we find today. The process took many thousands of years when Earth was still young.
If you think mining gemstones is a complicated and expensive process, what do you think about all the toil and turmoil Nature had to go through to gift us with these precious stones? How are gems formed on Earth is very complicated, very rare and fascinating. Here is an explanation of how it happened.

How are gems formed on Earth? The full story

The gemstones we see today are rarely kept in the natural form in which they were found. Either they are heat treated to bring out the vividness of their color, or they are cut, polished and set on jewelry to bring out their best sparkle and beauty. But gems are found in rocks that have many different minerals. Mineral crystals and gemstones are mined from these rocks.

How are gems formed on Earth? It’s a long process. But to summarize, minerals crystalize when adequate heat, pressure and the time for them to grow synchronize. It happens deep within the Earth but within the Earth’s crust. Diamonds and Peridots are formed in the Earth’s mantle. The rest are formed in the crust.

The Earth’s crust is made up of three types of rock, igneous, metamorphic and sedimentary rock. The igneous layer comprises of solidified magma (molten lava found deep within Earth). When the magma cools slowly in the crust, it can crystalize and form precious minerals. High pressure makes this hot fluid infiltrate surrounding rocks and makes chemical changes. Gemstones formed like this in igneous rocks include quartz, beryl, garnet, moonstone, apatite, diamond, tanzanite, topaz and zircon.

Over time these igneous rocks are pushed towards the Earth’s surface and are faced by erosion, weathering, and the actions of wind and water. Pressure and changes lead to the formation of sedimentary rocks. Gemstones in sedimentary rocks are jasper, opal and zircon.

The presence of intrusive magma in an area and or what is known as regional metamorphism will cause physical and chemical changes to igneous and sedimentary rock. This resulted in the creation of metamorphic rock. Gemstones found in metamorphic rocks are beryl, jade, lapis lazuli, turquoise, ruby and sapphire.
Rocks and minerals are constantly changing over time. This is called the rock cycle. Igneous rock can change into sedimentary or metamorphic and metamorphic into ingenious or sedimentary but given lots of time.

How are gems formed on Earth? The process is different for every gemstone that has its own unique recipe. Too much heat will melt quartz that needs only a little heat to form. Minerals like Pyrite, on the other hand, need high temperatures.

Another important ingredient for the process of gemstone formation is time. Time affects the quality and size of the gemstones formed. Crystals need time to grow, and it takes time for the atomic arrangements to order themselves. The presence of water also accelerates gemstone formation.

If the cooling process of the magma is rapid, then no crystals will form, which leads to the formation of volcanic glass. But if the cooling is very slow, spanning over millions of years, the crystals formed will be large, and there your gems will be formed.

Another way in which gemstones are formed is when rainwater seeps into the Earth and cracks in rocks. These mineral deposits form rain and lead to the formation of new crystals.

How are gems formed on Earth? Conclusion

Basically, there are four main processes by which gemstones are formed: Molten rock and associated fluids, metamorphism, surface water and Gems that are formed in the Earth’s mantle. For a rare instance in which a gemstone forms, the conditions of time, space, pressure and heat have to be just right. It’s fascinating but true. A slight variation in Nature’s recipe will cause flaws in the formation of the gemstones.

For a more detail explanation of how gemstones are formed please refer to this article by the International Gem Society.

Learn all about Moostones and Moonstone mining in Sri lanka. Take a journey through the Moostone mines of Ceylon.

*All pics are taken from Unsplash.com