its the brand new flourite. While not common, its no uncommon either to have a random plant sprout up.
its technically a terrestrial plant, so don't expect it to live long...but it might be fun to grow.
incidentally, I had a 5gallon i just setup again, with used flourite that was kept in a clean kitty litter tub, and sealed.
it had been stowed away for at least 5-6 months.
low and behold, I had 5 live snails crawl outta the flourite after I put water back in the tank, and a random sprout show up, but it only lived 2 days.
the snails are still fine. just little grey pond snails.