There is disclosed a mineral-based panel including a core, wherein the panel includes a mechanical locking system at respective opposite first and second edges for assembling a first panel in an assembled position with an adjacent second panel by means of a folding displacement and/or a vertical displacement of the adjacent panels; the first edge including a locking strip projecting beyond a vertical plane and a locking element projecting from the locking strip; the second edge including a downwards open locking groove configured to receive the locking element by means of said displacement for horizontal locking of the adjacent panels, wherein a first pair of horizontal locking surfaces includes a first locking surface provided by the locking element and a second locking surface provided by the locking groove. There is provided play between the first locking surface and the second locking surface during assembling of the first and second panel by means of said displacement.