We don't have synonyms for slich yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are slick, slice and lich.
(n) :
Alternative form of schlich. [(dated, mining) The finer portion of crushed ore, as of gold, lead, or tin, separated by the water in certain wet processes.]
(n) :
Alternative form of schlich. [(dated, mining) The finer portion of crushed ore, as of gold, lead, or tin, separated by the water in certain wet processes.]