n.砂岩漂砾
Bringing a sarsen stone to Stonehenge requires years of planning. 把岩石带到巨石阵是需要常年的计划的.
The closest source of the large sarsen stones is here at the Marlborough Downs, to the north of Stonehenge. 最近的石头资源是在万宝路低谷这儿，面对巨石阵北面的地方.
and the outer ring of huge sarsen stones was completed 500 years later. 而外环的砂岩石又在此后500年才完工。
sarsen stone 残留岩体
