Our client’s roof still contains the original slate tiles which appear to be about 100 years old, but some were broken and missing and needed to be replaced.  The original tiles were much smaller then those currently available on the market, so we had to cut them down to the appropriate size.  We also tried to match the colour as closely as possible, however the match will never be perfect because of available stock, wear of original tiles and the nature of stone.  In this case it was possible to repair some of the slate roof tiles because they were quite solid.  In other cases, the roofing slate may be of inferior quality and very soft, in which case it is very difficult to repair since many will break in the process.  Those borken must be replaced and the process is less cost effective then installing new slate tiles on the roof.  Below are some photos of such a case where the slate is so soft it easily breaks and turns into dust.