Some sandstones are resistant to weathering, yet are easy to work. This makes sandstone to be a common building and paving material. However, some that have been used in the past, such as the Collyhurst sandstone used in North West England, have been found less resistant, necessitating repair and replacement in older buildings. Because of the hardness of the individual grains, uniformity of grain size and friability of their structure, some kinds of sandstone are excellent materials from which to make grindstones, for sharpening blades and other implements. Non-friable sandstone can be used to make grindstones for grinding grain, e.g., gritstone. Such as Collyhurst sandstone is also a good material for building.