Rusticle

A rusticle is a formation of rust similar to an icicle or stalactite in appearance that occurs deep underwater when iron-loving bacteria attack and oxidize wrought iron and steel.

[2] Rusticles on the Titanic were first investigated in 1996 by Roy Cullimore, based at the University of Regina in Canada.

A previously unknown species of bacteria living inside the Titanic's rusticles called Halomonas titanicae was discovered in 2010 by Henrietta Mann.

The remainder of the structure is a complex community of symbiotic or mutualistic microbes including bacteria Halomonas titanicae and fungi that use the rusting metal as a source of food, causing microbial corrosion and collectively producing the mineral compounds that form the rusticle as waste products.

The outer surface of a rusticle is smooth red in appearance from the iron(III) oxide, while the core is bright orange due to the presence of crystals of goethite.