The restoration of the masonry of Notre-Dame de Paris Cathedral, following the fire which took place on the 15th April 2019, has been possible as a result of a planned and controlled supply of new stone. This success required collaborative work between geologists and architects. The different types of stone used in the monument through time have been identified for all the upper parts of the edifice. This naturally results in better historical and architectural knowledge about the edifice, but more importantly it allows for a targeted evaluation of the requirements for new stone. These requirements are on one hand, functional: knowing the dimensions of the blocks and the overall volumes required. On the other hand, they are qualitative: the necessity for hard stone in certain areas or more porous stones elsewhere, etc. The available resources in quarries have been reviewed and the production scheduled and monitored. The methodology used, which has enabled the restoration of the monument within a timeframe of 5 years, despite the significant requirements of stone (1000 m3), is detailed within this article.