The term phosphate rock or Phosphorite is widely used to refer any rock with high phosphorus content.

Estonian phosphorite rock ( 5-20% P content ) is a brownish-grey Obolus sandstone containing Lingula valves and detritus.  Given sedimentary ore also contains substantial amount of rare earth elements (REEs -  elements from lanthanum to lutetium).  As the world-wide demand for heavy REEs (HREEs) for high-tech industries is growing exponentially, the interest towards possibilities to use Estonian phosphorite is rising.