Gemstones, precious metals hold all this useful beauty | Science| In-depth reporting on science and technology | DW | 27.12.2018
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Gemstones, precious metals hold all this useful beauty

Gemstones and precious metals are pretty, and pretty useful, too. Cobalt, silver, diamonds...everywhere you look.

It's easy to take gemstones and precious metals for granted. They look nice. End of story. But that's just the half of it.

Take, for instance, diamonds, the hardest material in nature — the stylus on record players is essentially a diamond. Did you know that?

And what about cobalt — a beautiful, ocean blue gem, it's also used in electric car batteries and highly valuable as a result. But it gets a bad rap, as children are said to be forced to mine for it in dangerous conditions in the Democratic Republic of the Congo. 

Silver, too, has many uses beyond jewelry and tableware.

Read more: Marie Antoinette jewels fetch millions

So, in a Yuletide spirit of public service, here's a few interesting facts about gemstones and precious metals — how they form and some of their many uses.

1.   Gemstones and minerals are old… very old

As with the planet itself, the basic elements that become gemstones are at least as old as our solar system — around 4.5 billion years. Just think of asteroids, which are leftover objects from the formation of the solar system. Some are incredibly carbon-rich, and diamonds are essentially crystalized carbon. Asteroids can also hold platinum, gold, iron, nickel, and rare Earth minerals.

The oldest mineral on Earth is Zircon, which is estimated to be 4.4 billion years old when it's found in Australia.

2.   Gemstones come up like lava  

Precious stones and minerals tend to come from far beneath the Earth's surface. Some, such as diamonds and peridot, form in the Earth's mantle. The mantle is the largest layer of the planet that lies between the core and the outer crust. It's mostly populated by silicates, including the mineral olivine and garnet. Diamonds crystalize in magma just below the Earth's crust. These gems and minerals can be pushed up closer to the surface by volcanic eruptions, but they only survive as gems if the magma cools slowly. That's when it crystalizes and forms minerals. And they're mined in the crust.

3.   Four zones of stone

Gemstones that come from solidified magma form by a process called igneous. These can include quartz (like amethyst and citrine), beryl (like emerald and aquamarine), garnet, moonstone, apatite, tourmaline, topaz and zircon.

Some form in sedimentary rock when, for instance, ocean water deposits sediments. Those include opals, jasper, malachite and zircon. 

Then there are stones that form in metamorphic rock. Igneous and sedimentary rock can come under extreme heat and pressure through the movement of magma or tectonic plates. When this happens their chemistry and crystal structure changes — and they morph into gems like jade, turquoise, ruby, and sapphire.

And hydrothermal gemstones form when bodies of water rich in minerals cools and gets pushed up into cavities and cracks in the Earth, producing emeralds.  

4.   Diamond is the toughest of them all

The Mohs scale of mineral hardness was calculated in 1812 by a German scientist called Friedrich Mohs. Diamonds are at the top of the heap at number 10 — they are the hardest known mineral in nature. At the other end of the scale at number 1 is talc, a form of "soapstone," and the basis of common talcum or baby powder as it's good for absorbing liquids and smells. But it's also used in ceramics, paints, and plastics. Diamond consists of carbon atoms, similar to graphite, but it's the structure of those carbon atoms that makes diamonds so tough and graphite so soft. In fact, diamonds are so hard, they are used in industry to cut and drill other rocks.

5.   Found by 'early man'

You could say we take gemstones for granted as we tend to limit their use to jewelry. And the same is true of a precious metal like silver. It was discovered in approximately 3000BC, and it's often in jewelry. But it's also used in mirrors for its reflective properties. Silver salt — an inorganic compound of silver nitrate — is used in digital photography to protect against image piracy. Silver is also used in batteries, and other electronic things like circuit boards. And silver nanoparticles can even be woven into clothing to stop sweats and smells clinging to the material.         

6.   Science in the Scriptures

There are references to gemstones and precious metals throughout the Old and New Testaments. The Book of Exodus describes an ornate breastplate in great detail. It was worn by Aaron, who, with his brother Moses, led the Israelites out of Egypt. According to the scripture, the breastplate featured rope gold, topaz, ruby, sapphire, beryl, turquoise, agate and amethyst, onyx and jasper, emeralds and more. These are ancient stones. Emeralds, in fact, were first mined in Egypt, where Cleopatra adored the green gem. Later, Job writes about "a mine for silver and a place where is gold is refined" — so there are good indications of extraction and processing methods. Right up to the Book of Revelation. 

There are other elements, too — less pretty ones, such as sulfur. One of the fifteen times it's mentioned is in The Book of Genesis when "The Lord rained down burning sulfur on Sodom and Gomorrah." It was also known to the ancient Greeks, who burnt sulfur as a fumigant.  

7.   Prehistoric mining

We tend to think of mining today as a highly modern, partially automated, mega industry. And it is indeed that in some places. But clearly that's not how mining started. There is archeological evidence of mining even in prehistoric times, going back to 8000 BC. One of the oldest underground mines is located in eSwantini (formerly Swaziland) and dates back to 4100 BC. They mined hematite there — a principle component of iron. Hematite is said to have healing properties, but it was also used as a red chalk. Mines dating back to 5000 BC have been found in Poland and Hungary. The stone has been used for an estimated 164,000 years.

*With thanks to singer-songwriter Elvis Costello and the title of his 1996 album "All this useless beauty."

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