Diamonds are forever and Zircons are tooMany people have heard the saying ‘diamonds are forever’ but

Diamonds are forever and Zircons are tooMany people have heard the saying ‘diamonds are forever’ but very few know about Zircon, a mineral that, at the very least, should be recognised for its longevity. The zircon below (0.0157 inches long) from the Jack Hills in Australia is the oldest rock fragment on Earth at 4.375 billion years old! To put this in perspective, that is only 165 million years after the Earth formed and less than 100 million years later than the massive impact event that produced our moon.So what makes a Zircon so special? We have all heard of the impressive properties of diamonds, they sit at the top of the Mohs Scale of hardness after all, but this isn’t the only attribute you need to live forever.Zircon belongs to a group called the nesosilicates, a collection of minerals defined by isolated SiO4 ions that are connected by interstitial cations (small atoms or ions that occupy the space between larger ions or atoms), in this case Zirconium. The mineral can come in a wide variety of colours, with gem quality specimens known as Matura-diamonds due to their resemblance to the real thing.One of the key properties of Zircon is that it is chemically inert. This means it won’t react with other elements and therefore retains its chemical composition over time. It is also very hard, coming in at 7.5 on the Mohs Scale of Hardness; pretty impressive when you consider that a steel nail is only 6.5.Furthermore, zircon is present in sedimentary, igneous and metamorphic rocks, meaning it will be present in a wide variety of samples. The minerals also contain Uranium and Thorium, allowing them to be radiometrically dated even if they are billions of years old.So, how do you make sure you win the award for oldest piece of rock? It’s easy as one, two three:Be abundant - the more of you there are and the more rock types you can occur in the higher the chance you’ll be found at the surface!Be hardy - you’ve got a whole lot of weathering, erosion and chemical alteration to survive if you are going to exist for over 4 billion years (The zircon from Jack Hills is thought to have originally formed in a granite, a very different rock to the one it is hosted in now!)Be dateable - There is no point in existing for billions of years and making your way to the surface just so a geologist can look at how shiny you are! Containing radioactive Uranium and Thorium is a sure fire way of getting dated and appreciated for the wonder you really are!So there you have it, next time someone tells you diamonds are forever, just spare a thought for humble little Zircon, the oldest mineral on Earth.WatsonReferences:http://bit.ly/1DKiNUqhttp://bit.ly/1EgW6Fhhttp://bit.ly/1mBLj3QFurther Reading:http://bit.ly/1hPc5DOhttp://bit.ly/1FDLUrIImage Credit: John Valley – Univeristy of Wisconsin-MadisonRob Lavinsky - Irocks.com -- source link

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