They're targeting a pilot within the next 5 years on a single beach, which should help towards figuring what side effects exist. They also note there exist nat

They're targeting a pilot within the next 5 years on a single beach, which should help towards figuring what side effects exist. They also note there exist naturally occurring green sand beaches (https://en.m.wikipedia.org/wiki/Papakolea_Beach https://en.m.wikipedia.org/wiki/Papakolea_Beach), though those are tourist spots and probably haven't been deeply studied.