PERIDOT | PALLASITE FUKANG
Posted on 12 August 2014
The 146.10 cts peridot is in the collection of the Natural History Museum in London
Peridot is one of the few gemstones that occur in only one colour, an olive green. However, the intensity and tint of the green depends on how much iron is contained in the crystal structure, so the colour of individual peridot gems can vary from yellow- to olive- to brownish green. The most valued colour is a dark olive green.
Olivine is a common mineral in mafic and ultramafic rocks and is a very abundant mineral in general. However, gem quality peridot is rather rare, the mineral is precious. It is often found in lava and in the mantle, which lava carries to the surface, but quality peridot only occurs in a fraction of these settings. Peridot can also be found in meteorites. A famous Pallasite meteorite, from which peridot crystals were collected from, was offered for auction in April 2008 with a requested price of close to $2.7 million at Bonhams, but remained unsold.
Peridot olivine is mined in Egypt, North Carolina, Arizona, Hawaii, Nevada and New Mexico. It is also found in Australia, Brazil, China, Kenya, Myanmar (Burma), Norway, Pakistan, Saudi Arabia, South Africa, Sri Lanka and Tanzania. The largest cut peridot is a 311 carat (62g) specimen in the Smithsonian Museum in Washington D.C. Peridot is the birthstone for the month of August
The 420kg Pallasite Fukang
The world’s most magnificent meteorite discovery of the 21st century is the 420kg Pallasite Fukang. The namesake is from the region it was found; discovered near Fukang, Xinjiang Uygar Province, China in 2000. It contains spectacular olivine crystals; those of gem-quality are classified as peridots, which are sometimes referred to as the gemstones from outer space. So far their highly refractive translucent crystals are unmatched by those contained in other pallasites. Only about 1% of all meteorites are pallasites making them extremely rare and those composed of approximately 50% olivine and 50% nickel-iron are thought to be relics of forming planets.
The value of the Fukang specimen lies greatly with its coming of existence. It was found as the sole specimen rather than the mass of the meteorite. On entering the Earth’s atmosphere a meteorite would explode on impact, sometimes even the main mass vaporises. The Fukang pallasite overcame the atmospheric and impact forces to present itself and its rare olivine crystals to Earth. The pallasite is thought to be 4.5 billion years old, which is also the same age as our solar system. This is based on the studies into its structure.
In order for the crystalline structure to form, the metal matrix cooled at the rate of a few degrees per million-year period. The nickel-iron matrix containing the space gems is classified as medium octahedrite due to the size of the crystal structures. These structures are known as Widmanstatten patterns and are diagnostic of extraterrestrial nickel-iron metal. Fukang has been cut and polished to display, to our knowledge, the largest cross section (36inch x 19inch) of phenomenal mosaic extraterrestrial crystals.