although the documentation says: https://github.com/mapbox/simplestyle-spec/tree/master/1.1.0 maki icons will be supported as markers, there are some maki icons not supported.
e.g. mountain, which is essential as there are many articles on mountains and this is the natural icon, I guess.
(same for volcano, stadium, castle)
See https://de.wikipedia.org/wiki/Hilfe:Kartographer/Maki_Icons#/maplink/0 for the gaps. (generated with <maplink> iterating over all the icons)