Rusticle
Encyclopedia
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 shipwreck
s.
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
.
compounds including iron oxide
s, iron carbonate
s and iron hydroxide
s. The remainder of the structure is actually 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 as waste products and hence forming the rusticle.
Since rusticles are found on wrought iron rather than other ferrous
metals, it is supposed that the microbes also use the sulfur
and phosphorus
impurities found in the metal.
. They are very delicate and can easily disintegrate into fine powder on even the slightest touch.
in appearance from the iron (III) oxide, while the core is bright orange
due to the presence of Goethite
(a hydrated iron oxide) crystals.
Rust
Rust is a general term for a series of iron oxides. In colloquial usage, the term is applied to red oxides, formed by the reaction of iron and oxygen in the presence of water or air moisture...
similar to an icicle
Icicle
An icicle is a spike of ice formed when water dripping or falling from an object freezes. Typically, icicles will form when ice or snow is melted by either sunlight or some other heat source , and the resulting melted water runs off into an area where the ambient temperature is below the freezing...
or stalactite
Stalactite
A stalactite , "to drip", and meaning "that which drips") is a type of speleothem that hangs from the ceiling of limestone caves. It is a type of dripstone...
in appearance that occurs underwater when wrought iron
Wrought iron
thumb|The [[Eiffel tower]] is constructed from [[puddle iron]], a form of wrought ironWrought iron is an iron alloy with a very low carbon...
oxidizes. They may be familiar from underwater photographs of shipwreck
Shipwreck
A shipwreck is what remains of a ship that has wrecked, either sunk or beached. Whatever the cause, a sunken ship or a wrecked ship is a physical example of the event: this explains why the two concepts are often overlapping in English....
s.
The word rusticle is a portmanteau of the words rust
Rust
Rust is a general term for a series of iron oxides. In colloquial usage, the term is applied to red oxides, formed by the reaction of iron and oxygen in the presence of water or air moisture...
and icicle
Icicle
An icicle is a spike of ice formed when water dripping or falling from an object freezes. Typically, icicles will form when ice or snow is melted by either sunlight or some other heat source , and the resulting melted water runs off into an area where the ambient temperature is below the freezing...
and was coined by Robert Ballard
Robert Ballard
Robert Duane Ballard is a former United States Navy officer and a professor of oceanography at the University of Rhode Island who is most noted for his work in underwater archaeology. He is most famous for the discoveries of the wrecks of the RMS Titanic in 1985, the battleship Bismarck in 1989,...
, 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
University of Regina
The University of Regina is a public research university located in Regina, Saskatchewan, Canada. Founded in 1911 as a private denominational high school of the Methodist Church of Canada, it began an association with the University of Saskatchewan as a junior college in 1925, and was disaffiliated...
in Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
.
Composition
The rusticle consists of up to 35% ironIron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
compounds including iron oxide
Iron oxide
Iron oxides are chemical compounds composed of iron and oxygen. All together, there are sixteen known iron oxides and oxyhydroxides.Iron oxides and oxide-hydroxides are widespread in nature, play an important role in many geological and biological processes, and are widely utilized by humans, e.g.,...
s, iron carbonate
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....
s and iron hydroxide
Hydroxide
Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and a hydrogen atom held together by a covalent bond, and carrying a negative electric charge. It is an important but usually minor constituent of water. It functions as a base, as a ligand, a nucleophile, and a...
s. The remainder of the structure is actually a complex community of symbiotic
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...
or mutualistic microbes including bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
Halomonas titanicae
Halomonas titanicae
Halomonas titanicae is a species of bacteria which was found on rusticles in the wreck of the RMS Titanic....
and fungi that use the rusting metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
as a source of food
Food
Food is any substance consumed to provide nutritional support for the body. It is usually of plant or animal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals...
, causing microbial corrosion
Microbial corrosion
Microbial corrosion, also called bacterial corrosion, bio-corrosion, microbiologically-influenced corrosion, or microbially-induced corrosion , is corrosion caused or promoted by microorganisms, usually chemoautotrophs...
and collectively producing the mineral compounds as waste products and hence forming the rusticle.
Since rusticles are found on wrought iron rather than other ferrous
Ferrous
Ferrous , in chemistry, indicates a divalent iron compound , as opposed to ferric, which indicates a trivalent iron compound ....
metals, it is supposed that the microbes also use the sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
and phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
impurities found in the metal.
Structure
Structurally, rusticles contain channels to allow water to flow through, and they seem to be built up in a ring structure similar to the growth rings of a treeTree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
. They are very delicate and can easily disintegrate into fine powder on even the slightest touch.
Colours
The outer surface of a rusticle is smooth redRed
Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 630–740 nm. Longer wavelengths than this are called infrared , and cannot be seen by the naked eye...
in appearance from the iron (III) oxide, while the core is bright orange
Orange (colour)
The colour orange occurs between red and yellow in the visible spectrum at a wavelength of about 585–620 nm, and has a hue of 30° in HSV colour space. It is numerically halfway between red and yellow in a gamma-compressed RGB colour space, the expression of which is the RGB colour wheel. The...
due to the presence of Goethite
Goethite
Goethite , named after the German polymath Johann Wolfgang von Goethe, is an iron bearing oxide mineral found in soil and other low-temperature environments. Goethite has been well known since prehistoric times for its use as a pigment. Evidence has been found of its use in paint pigment samples...
(a hydrated iron oxide) crystals.