naslaga

1. layer; build-up; deposit
   Na polici je debela naslaga prašine. — There's a thick layer of dust on the shelf.
   Sirće skida naslage kamenca sa slavine. — Vinegar removes limescale build-up from the tap.
2. (in geology) stratum; deposit
   U ovoj oblasti pronađene su naslage uglja. — Coal deposits were found in this area.

Often plural: masne naslage means fat deposits.