Some diamonds come from depths of more than 650km. Tiny imperfections in these gems give us clues about what’s happening in Earth’s hidden geological layers.
Diamond or zirconia? Apart from the price, it can be hard to tell these two gems apart.
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Zirconia is a mineral with a crystal structure made from the elements zirconium and oxygen. It looks pretty like diamond, but is only worth a fraction of the value.
Sapphires and rubies are both crystals of the mineral corundum - but with different impurities to create blue and red hues. Australian sapphires are renowned for being inky blue.
What makes a stone a gem? It boils down to a few key qualities: beauty and durability. But opal, the national gemstone of Australia, is an anomaly - it’s soft.