Because they have a bluish tinge to their colour.
sarsens
Stonehenge phase 1 is the circular earth works that forms the outer part of the monument. The sarsen stones and blue stones are in the center of the earthworks.
The blue stones at Stonehenge came from the Prescelly mountains in south Wales.
Stonehenge is a monument that is made out of large stones. There is a circle of stones in Stonehenge, with several stones laying on top of the vertical stones.
There are 92 stones at Stonehenge at the present time
Stonehenge
They are actually called saphires
The prehistoric monument of Stonehenge
It is believed that all the stones in Stonehenge weigh over 320 tons.
There are other round circles of standing stones in the UK but there is only one called "Stonehenge" near Amesbury, Wiltshire
Stonehenge is made up of an estimated 80-82 stones, consisting of large Sarsen stones, smaller Bluestones, and other stones in various formations.
Giant stones (e.g. the Stonehenge stones) from prehistoric times.