Scientists have unearthed a more than 3,300-year-old stone stone tool which they say led them to rediscover a "lost" 20th-century manuscript and a "geochemically extraordinary" bit of earth.

Found from Emirau Island in the Bismark Archipelago off the coast of New Guinea, the two-inch stone tool was probably used to carve, or gouge, wood.

It seems to have fallen from a stilted house, landing in a tangle of coral reef that was eventually covered over by shifting sands, the researchers said. The jade gouge, they said, may have been crafted by the Lapita people, who appeared in the western Pacific around 3,300 years ago, then spread across the Pacific to Samoa over a couple hundred years, and from there formed the ancestral population of the people we know as Polynesians.

Jade tools have been found before in these areas, but what's interesting about the object is the type of jade it's made of -- it seems to have come from a distant region, and perhaps these Lapita brought it from wherever they originated. It's missing certain elements and has more-than-expected amounts of others, suggesting the stone came from another geological source. But the researchers aren't sure where.

The only chemical match the researchers knew of was a site in Baja California Sur, Mexico, but it's unlikely that Neolithic people could have transported it across the Pacific at that time. However, they couldn't find any other explanations for its composition. And that is, until they came across a lost 20th-century German manuscript by C E A Wichmann who describes about some curious rocks he brought from Indonesia in 1903.

It's about 1,000 kilometers from the site where the jade tool was found, but the chemical properties he reported seem very similar to that of the artifact, said the researchers who detailed their work in the European Journal of Mineralogy. (More) PTI SKP AKJ

"In the Pacific, jadeite jade as ancient as this artifact is only known from Japan and its usage in Korea," Study author George Harlow, of the American Museum of Natural History in New York, said: "In the Pacific, jadeite jade as ancient as this artifact is only known from Japan and its usage in Korea.

"It's never been described in the archaeological record of New Guinea.

"When we first looked at this artifact, it was very clear that it didn't match much of anything that anyone knew about jadeite jade." Its chemical composition "makes very little sense based on how we know these rocks form," Harlow added.

Researchers are now investigating those samples to see if modern techniques can prove that the tool came from Indonesia. The jadeite jade source, if found, would be "something geochemically extraordinary," they added.

Jade is a general term for two types of tough rock, those made of jadeite jade and another group of nephrite jade. The stones are both greenish in color, but nephrite jade is slightly softer, while jadeite jade is scarcer, mostly found in cultures from Central America and Mexico before Europeans arrived.