A moon crater on Earth? Visit Siberia's Treasure Mountain, source of platinum crystals

Remote in Khabarovsk region, this mysterious 8 kilometre (5 mile) wide feature some 600 metres (2,000 feet) high is the source of some of the world's rarest metals. 

Experts say the most likely cause of this geological curiosity - seen in pictures here from space - is neither an ancient volcano nor the carnage caused by a meteorite strike, although both were long-held theories. 

Instead, an 'intrusion' was caused when molten magma of igneous rock crystallised below the surface more than one billion years ago, forming a perfectly circular rocky ring.

It has been since exposed by erosion to appear on the surface.

'Harder then the rest of the earth around it, the Kondyor Massif intrusion - in this case an alkaline-ultrabasic massif intrusion - has slowly made its way through 5,000 miles of mantle and is now visible on the surface of the Earth,' says one account. 

'A stream flows out from its centre, fuelled by the snow waters melting from the Kondyor Massif's 2000-foot-high rim.'

In fact other smaller feeder streams flow inwards from the rim feeding the Kondyor River which exits through a gap on the north side of the massif. 

These streams contain placer deposits of platinum crystals, nuggets and grains, plus gold and other platinum minerals. Some of the crystals are very sharp, while others show minimal rounding on the edges and corners. 

It is the site of a platinum mine, but is also a source of gold, and in addition exceptionally rare gold encrusted platinum crystals. They are said to be the 'finest ever found' in the world.

This Treasure Mountain even has its own special mineral known as Konderite, which combines copper, platinum, rhodium, lead, and sulphur. Mining for plutonium is said to have begun here in 1984, in the ebbing years of the Soviet Union. 

Platinum crystals from Kondyor first appeared at the Tucson Gem and Mineral Show, in the US, in 1993, where they were an 'instant sensation', it was reported.

This unique feature is located 600 km (373 miles) west-to-southwest of Okhotsk, and some 570 km (354 miles) south-east of Yakutsk. For comparison it is almost seven times the diameter of Meteor Crater in Arizona. Typically four tons of platinum were mined here annually.