ON THE surface, this 16.4-tonne "freak of nature" isn't much to look at but veteran sapphire miners Jenny and Jim Elliot say this semi-precious gemstone is one of, if not the world's biggest boulder of Australian jade.
"To find a big boulder like this is unheard of; it's absolutely rare and unlike anything ever found anywhere in the world," Jim said.
Having spent close to a decade decorating the Elliots' driveway in Calliope, this impressive chunk of Marlborough chrysoprase (also known as Australian jade) was donated by the Elliots to the National Rock Garden in Canberra.
The $10 million federally funded National Rock Garden was developed by the Geological Society of Australia and will display more than 100 rock specimens from around the country.
Professor Brad Pillans, who sits on the board of directors at the rock garden, said each rock had been chosen in order to tell a part of Australia's history.
"The Marlborough area is world famous for chrysoprase and the Elliots' specimen would have to be one of the best," he said.
Chrysoprase is usually found in thin bands or in "bits and pieces".
The Elliots initially tried to sell the boulder in China, where it could be carved up and turned into jewellery, but the logistics of getting the mammoth rock overseas was too great. "And anyway we've got to preserve these things for Australians. It's important," Jim said.
Jenny was glad it was going to a good home. "But I'm not sure how the little bonsai gum growing out the top will go with the cold in Canberra."
The Elliots' boulder is expected to reach Canberra by tomorrow where it will be put in storage until the rock garden is completed.