Stonehenge may be still standing because of the unique geochemical composition of the standing stones.
An international team of scientists analysed wafer-thin slices of a core sample from one of the great sandstone slabs, known as sarsens, under a microscope.
The 3.5-foot-long sample, called Philip's Core, was extracted more than 60 years ago.
The analysis shows the sarsen is made up of mainly sand-sized quartz grains that are cemented tightly together by an interlocking mosaic of quartz crystals.
This explains the stone's resistance to weathering over the last 5,000 years and why it made an ideal material for building such a monument.
Chemical data from the Phillip's Core were used last year to show that most of the large sarsen stones came from around 15 miles to the north, in West Woods on the edge of the Marlborough Downs, Wiltshire.
The study was led by Professor David Nash at the University of Brighton and involved geologists, geomorphologists and archaeologists from institutions including British Geological Survey, English Heritage and the Natural History Museum.
It is extremely rare as a scientist that you get the chance to work on samples of such national and international importance,' said Professor Nash.
'This small sample is probably the most analysed piece of stone other than Moon rock!'
Sarsens were used to construct Stonehenge and other prehistoric stone circles, such as those around the Wiltshire village of Avebury.
Typically weighing 20 tonnes and standing up to 7 metres tall, sarsens form all 15 stones of Stonehenge's central horseshoe, the uprights and lintels of the outer circle, as well as outlying stones such as the Heel Stone, the Slaughter Stone and the Station Stones.
Researchers were gifted a unique opportunity to analyse Philip's Core, the narrow cylindrical sample, which was drilled from Stone 58 at Stonehenge during conservation work by British firm Van Moppes in 1958.
It revealed the interlocking quartz cements developed through at least 16 cycles of mineral deposition, most likely as a result of wetting and drying while the sediment was buried underground.
According to the experts, no previous investigation has analysed a single sarsen boulder with such a range of complementary techniques.
Professor Nash said the data will support future research on sarsens at Stonehenge and other nearby Neolithic monuments.
The study has been published in the journal PLOS One.
