Now we opened the discussion properly.... and I'm pleased somebody has noticed... that the 'bluestones'... only 'Appear' to be blue, and they were given that epithet by Antiquarians (their 'apparent' colour hasn't changed much if At All in the last couple of hundred years).
They were Not blue, when they were erected. They are not all the same type of stone. There are four main types of rock (at Stonehenge) which the antiquarians termed bluestones. They are:-
dolerites, spotted dolerite, rhyolite, volcanic ash.
Other stones (such as the 'Altar stone') are other types, such as sandstone.
In 1923, H.H. Thomas went to Wales in search of rocks which might match those at Stonehenge... and found them near Presli... and so the Welsh connection was underpinned. But was it really their source?
Not to put too fine a point on it... the single biggest source of 'bluestone' axes in the British Isles, Is Langdale in the Lake District. Now, there, we have volcanic ash (Langdale Tuff), which is Truly blue-grey in colour... and yes, the colour of That particular rock-type certainly was One of the reasons those axes were so highly prized, and distributed throughout Britain in the Neolithic.
Have we been looking in the wrong direction all this time? Were the bluestones in fact, from Cumbria? where all those rock-types outcrop (as well as in Wales)? and was Thomas a member of the secret order of Druids? (therefore his choice of Wales as the source of the bluestones might not be impartial?).