Key Points:

Rare Maori artifacts, including an unusual pounamu hei tiki, are being auctioned in New York tomorrow (NZT) as part of a collection estimated to be worth up to US$11.5 million ($20.7 million).

Sotheby's is offering the Maori items - expected to sell for up to US$128,000 - as part of 135 lots of Oceanic and African art from renowned American collectors Frieda and Milton Rosenthal.

The big hei tiki, carved with stone tools from a piece of pounamu originally cut to be an adze, is expected to sell for between US$40,000 and US$60,000.

The 16cm-tall tiki is unusual in that its chin rests on the right shoulder, instead of the left. It has inset black-lip pearl oyster eyes.

The tiki's condition is described in the catalogue as very good overall, although signs of wear and tear include a chip on the forehead, a broken upper eye and minor nicks and scratches.

It is among items acquired by collector Harry Beasley, who died in England in 1939. The items were purchased from Mr Beasley by New York collector John J Klejman, who then sold them to the Rosenthals in the 1970s.

Another, smaller, tiki is expected to sell for US$18,000. According to a handwritten label, it dates to the 18th or 19th century.

Also up for auction is a finely carved lidded box, or waka huia, estimated to fetch up to US$30,000.

In October, a waka huia sold at a Sotheby's auction in Sydney for A$57,600 ($68,000) against its pre-sale estimate of A$15,000-A$20,000, attracting strong interest from overseas collectors.

An elaborately carved 18th century wahaika, or hand club, is expected to sell for as much as US$15,000, and a 1.87m long staff has an estimated price of up to US$5000.

The Ministry of Culture and Heritage monitor auctions within New Zealand, but do not follow those held overseas.

"We have no ability under legislation such as the Protected Objects Act 1975 to stop the sale, or force the repatriate of cultural heritage material sold at auction overseas," a spokeswoman said.

- NZPA