Black → blacken (to make black)
e.g.: a blacken wall

gold →golden (made of gold)
e.g.: a golden watch

Silk →Silken(made of silk)
e.g.: a silken tie

Wood →wooden (made of wood)
e.g.: a woolen pull over. Woolen blanket.

Full of characterized by dirt →dirty (full of dirt)
e.g.: a dirty kitchen.

Rain →rainy → (characterized by rain) →a rainy season

Salt →salty (full of salt)
e.g.: a salty soup.

Note: Y can also mean to be like
silk →silky (a silky table cloth)

Bush →bushy (a bushy hair that looks like a bush)