Unable to answer "What’s the surface here?" – Camino real Guane - Barichara (Path) – https://osm.org/way/87161412 via StreetComplete 63.0:

Parts are rocky, parts are just compresesed soil, sometimes very clayish. Very slippery when wet.
Its a hikingtrail!

Attached photo(s):
https://streetcomplete.app/p/340821.jpg
https://streetcomplete.app/p/340822.jpg