Tubular stalactites, also known as soda straws. Their existence next to a traversed cave path is rare – usually getting knocked off by passers by. I was fortunate to see them on my tour of Round Spring Cave in Missouri. Undisturbed specimens have been recorded at 30 feet long.
Water seeping through the rock drips from the ceiling leaving minerals behind. The hallow center is formed by a blockage – preventing the stalactite from filling in.
Growing only a few millimeters per year, this formation is about as older as I am.
Learn more here. Near Shannon County Missouri 2012.