HARD SURFACE • DICTIONARY ONE.COM • Definition of Hard surface

... bit softer than spinel, and the rough crystals show a very perfect basal cleavage. That is, they will cleave in a plane parallel to the bases of the usual orthorhombic crystals. This being the case a cut topaz is very likely to be damaged by a blow or even by being dropped on a hard surface, and it would be wiser not to set such a stone in a ring unless it was to be but little used, or used by one who would not engage in rough work while wearing it. Thus a lady might wear a topaz ring on dress occasions for a long time without damaging it, but it would not do for a machinist ...

— A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public • Frank Bertram Wade

... to appear in long lines of delicate pale yellowish green. This is a most anxious time. Should rain fall, the whole surface of the earth gets caked and hard, and the delicate plant burns out, or being chafed against the hard surface crust, it withers and dies. If the wind gets into the east, it brings a peculiar blight which settles round the leaf and collar of the stem of the young plant, chokes it, and sweeps off miles and miles of it. If hot west winds blow, the plant gets black, discoloured, burnt up, ...

— Sport and Work on the Nepaul Frontier - Twelve Years Sporting Reminiscences of an Indigo Planter • James Inglis