Did you know?

February 8, 2009

Did you know that the hardest natural substance on earth is also “a girl’s best friend”?……It is, of course, diamond!

Did you know also know that “hardest” of the world’s diamonds have come from just two locations, in the Gwydir area, of eastern Australia?

One site is 50km to the east of Bingara, at Copeton, the other, The Bingara Field, is about 10km west of Bingara township. Since first discovered in 1872, about 500,000 carats of diamonds have been taken from these two sites.

The diamonds from the Bingara Field average about 1/3 of a carat in size and are mostly of gem quality. But when first sent to Antwerp, in Europe, in the 1870’s, to be “cut”, they were found to be “too hard” and so were mostly used in the cutting and polishing of other gems.

The BIG mystery though, is where did they come from?

Most of the world’s diamonds come from deep down in the earth’s crust. They are formed under high temperature and pressure then forced closer to the surface by flows of molten rock. Many are destroyed in the journey but some survive to be available on the surface as rare gems where water may carry them to be scattered in streams.

Some remain concentrated around the “craters” formed by the “pipes” that brought them to the surface. Some miners, like those in South Africa, even “chase” these pipes thousands of metres, deep underground, looking for diamonds.

The Bingara area is different to most of the world’s famous diamond areas. The earth’s crust is quite thin here. Geologists have struggled to explain why there are any diamonds here at all.

The current theory is that they were formed, hundreds of millions of years ago, when the ocean plate to the east of Australia, slid below the continental plate of mainland Australia. This is called “subduction”, and the heat and pressure of the movement may have formed the diamonds, nearer to the surface, from carbon based material caught in the squeeze. Diamonds are mainly made of carbon.

The Bingara Field diamonds have been carried to their present site by an ancient stream BUT they are not rounded or polished by long periods tossed in water, which suggests that they were not carried far. Their source might be fairly close by.

Finding the source of the Bingara diamonds, and the ancient pipes, has been a real challenge. In recent years, two companies have been using the latest technology, include magnetic surveys from aircraft, searching for a source. One company believes that the source is to the north in the Gravesend-Warialda area. The other, thinks that the diamonds came from the Upper Horton area to the south. Whatever the answer, the discovery process continues.


Related article

May 5, 2008
Mining company involved in “Discovering Gwydir” too!