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Unit Weight of Rocks

Unit weight or rock γ

Rock strength

Rock category (examples)

Unit weight of rock γ [kN/m3]

Solid rock

most hard solid rock, intact, compact and  dense quartz rock and basalt, other extraordinary hard rocks

28.0 - 30.0

Highly hard rock

very hard granite rock, quartz porphyry, very hard granite, hard flinty shale, quartzite, very hard sand rock, and very hard calcite

26.0 - 27.0

Hard rock

granite, very hard sandstone and calcite, quartzite lode, hard conglomerate, very hard ore, hard limestone, marble, dolomite, pyrite

25.0 - 26.0


sandstone, ore, medium sandy shale, flagstone


Medium rock

hard mudstone, softer sand rock, and calcite, chalky clay

23.0 - 24.0

Soft rock

shale, soft limestone, chalk, salt rock, frozen ground, anthracite, marl, remolded sandstone, soft conglomerate, ground with fels

22.0 - 26.0

Weak soil

compact clay, soil eluvium, black coal

20.0 - 22.0

18.0 - 20.0

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