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1. A bluish-gray sandstone used for paving and building.
2. A stone similar to this kind of sandstone.
1. (Geological Science) a blue-grey sandstone containing much clay, used for building and paving
2. (Elements & Compounds) the blue crystalline form of copper sulphate
3. (Geological Science) a blue variety of basalt found in Australia and used as a building stone
a bluish sandstone.