bluestone

名词 bluestone:

1. bluish-grey sandstone used for paving and building

blue.stone

n.（名词）
A bluish-gray sandstone used for paving and building.
青石，蓝砂岩：一种蓝灰色的沙岩，用于砌路或建筑
A stone similar to this kind of sandstone.
蓝矾：一种与蓝砂岩相似的石头