Wiktionary
n. an icicle-shaped object made out of rust
Wikipedia
A rusticle is a formation of rust similar to an icicle or stalactite in appearance that occurs underwater when wrought iron oxidizes. They may be familiar from underwater photographs of shipwrecks, such as the RMS Titanic and the German battleship Bismarck. Rusticles are created by microbes that consume iron.
The word rusticle is a portmanteau of the words rust and icicle and was coined by Robert Ballard, who first observed them on the wreck of the Titanic in 1986. Rusticles on the Titanic were the first investigated in 1996 by Roy Cullimore, based at the University of Regina in Canada. A new species of bacteria living inside the Titanic's rusticles called Halomonas titanicae was discovered in 2010. Henrietta Mann, the scientist who discovered the bacteria, has estimated that the Titanic may collapse circa 2030.
Rusticles can form on any submerged steel object and have been seen on other subsea structures such as mooring chains and subsea equipment. They form more rapidly in warmer climates and can form in water with little to no dissolved oxygen.
Usage examples of "rusticle".
At first, they saw only what previous tethered cameras had already photographed: the rusticles suspended from the ceiling of the Grand Staircase foyer, looking for all the world like stalactites hanging from the roof of an underground cave.