New Delhi, May 1 (IANSlife): Christies presents NWA 12691, a significant lunar rock, among the largest known in existence. Moon rock is among the rarest substances on Earth, with less than 650 kg. of lunar meteorites known to exist.

This example is the fifth largest piece of the Moon on Earth, larger than any returned by the Apollo programme. Valued in the region of £2 million, the specimen is available for immediate purchase via Christie's Private Sales.

Lunar meteorites arrived on Earth after having been blasted off the lunar surface by the collision with an asteroid or comet. All of the Moon's large craters were created by such impacts. This particular meteorite was part of a large meteorite shower straddling the Western Saharan, Algerian and Mauritanian borders, responsible for nearly half of all known lunar meteorites.

Approximately 30 different meteorites were collected, analysed, classified and assigned different NWA numbers in the belief they might be from different events and represent different lunar samples; but it has been determined that they all originate from the same lunar impact event as the current offering, NWA 12691, found in the Sahara Desert two years ago.

James Hyslop, Christie's Head of Science & Natural History: "I've been lucky enough to handle a few lunar meteorites at Christie's over the years, but every time I see this specimen in the warehouse the sheer size of it bowls me over. Weighing over 13.5kg, it is so much larger than anything else that has ever been offered before. The experience of holding a piece of another world in your hands is something you never forget."

Scientists identify Moon rocks by their specific textural, mineralogical, chemical and isotopic signatures. Many of the common minerals found on Earth are rare or absent on the Moon, while some lunar minerals are unknown on Earth. In addition, Moon rocks contain gases captured from the solar wind with isotope ratios very different from the same gases found on Earth.

Christie's will also offer for private sale a group of 13 aesthetic iron meteorites. Shaped by forces terrestrial and extra-terrestrial, this group of natural sculptures forms one of the most important collections of aesthetic iron meteorites in private hands. The collection, estimated in the region of £1.4 million, is available for immediate purchase via Christie's Private Sales.

Unknown millennia ago - the exact date is lost to prehistory - an object weighing more than 26,000kg crashed into Earth. It originally formed 4.5 billion years ago from the core of a planetary- like body located between Mars and Jupiter, whose shattered remains are now part of the asteroid belt. An impact event ejected what was to become the Gibeon mass into interplanetary space before its descent to Earth, exploding in the atmosphere and raining down on what is now the Kalahari Desert.