If you walk into a Costco, Home Depot or Lowe’s and order a countertop for your kitchen renovation, the store will likely contract with a local fabrication shop, instructing them to make one from a material called engineered stone. Often marketed as “quartz,” engineered stone is a synthetic product that contains up to 95% finely ground quartz mixed with polyester resins and pigments. The ease with which consumers can order it obscures the fact t…