backgrounds classifications colors colours edge edges mollusc mollusk pearly pitted ridge ridges rim rough seashells shapes sharp shells Sizes smooth spiral spiraling spiralling surface texture textures turns twists types variety abstract appearance background color colored colour coloured external fired glazed glazing hard layered layers lumps lumpy molten pottery surfaced surfaces surfacing textured thick thin Alice Springs Australia brown bush central Australia desert-country desert-region dry gully height high hot inland outback rocks rocky rugged scrub shrubbery sunlight sunshine terrain trees