SPC, Stone Polymer Composite, was introduced as an alternative to WPC flooring.  SPC has an extruded Calcium Carbonate core with fewer emulsifiers giving it additional density for greater impact resistance.  It also resists plank expansion and contraction in extreme temperature swings; this is due to the absence of the layer of Luxury Vinyl and dense core.  Just like WPC, it can float over most substrates and offers superior resistance to standard household spills and moisture.