Brick

Bricks made of zero-balanced dwarf star alloy made up the cell which held the Eleventh Doctor in Area 51 in 1969, though its true purpose was to give the Doctor and his friends a safehouse hidden from detection by the Silence. (TV: Day of the Moon)

The Tenth Doctor claimed to have seen Daleks crush bricks with ease using their suction arms. (PROSE: Prisoners of the Daleks)