The price of rhino horn, which is used as an aphrodisiac in Chinese medicine, has skyrocketed over the past few years, as the animal becomes rarer and China’s wealth increases, driving demand.

It is believed the buyer at the auction, held on March 14, was of Asian background, but Lawson’s general manager, Simon Hill, declined to confirm other than to say it was "a private buyer".

“We had several bidders on the phone both here and overseas and some bidders in the room. In the end it went to the bidder in the room," he said.

Mr Hill  said it was wrong to assume that the antique horns would end up ground into powder.

"I have Asian Australian clients who have bought them to display as a symbol of wealth and as an investment," he said.

The rising wealth in countries like China and Vietnam has pushed demand for rhino horn, which is used as an aphrodisiac or sometimes as status symbols to be displayed on the wall of wealthy Asians.

But getting hold of rhino horn is increasingly difficult, as most countries have signed a 1971 treaty which restricts trading in artefacts made from endangered species, including rhinoceros and elephant tusks. But items made before that date can still be traded.

This particular example belonged to an elderly man, who had inherited it from a relative.

"His wife and daughter thought it was hideous and made him keep it under the house. But he knew it was valuable, and his son was getting married so he wanted the money toward the wedding," Mr Hill said.

"It probably dates to the 1920s, perhaps earlier. We had to provide details of its provenance to the Department of the Environment, before we could auction it."

Mr Hill said the buyer had asked about getting an export licence but said this would be quite difficult to obtain.

In January, rhino horns with a street value of more than $6 million were seized by customs officials in Thailand and Singapore, according to a report released by Traffic, the wildlife trade monitoring network.

Almost 44 kilograms of rhino horn were discovered en route to Vietnam, where one kilogram of horn sells for about $120,000.

In Europe there have been more than 60 break-ins at natural history museums since 2010, with the thieves targeting rhino horns. Sometimes they are just snapped off the taxidermied animals. To combat the trade, Europe is establishing a DNA database and some museums have taken the precaution of replacing the real horns with resin replicas.

Rhinos are listed as a critically endangered species and only about 25,000 remain in the wild, a fraction of the 100,000 that roamed Africa in the early 20th century.

According to a South African report, 2013 was the worst year on record for rhino poaching, with 1004 animals killed, a 50 per cent increase on the previous year.