Hydrogen production

The serpentinization reaction involving the transformation of fayalite (Fe-end member of olivine) by water into magnetite and quartz also produces molecular hydrogen H₂ according to the following reaction:

${\displaystyle {\ce {3 Fe2SiO4 + 2 H2O -> 2 Fe3O4 + 3 SiO2 + 2 H2}}}$

This reaction closely resembles the Schikorr reaction also producing hydrogen gas by oxidation of Fe²⁺ ions into Fe³⁺ ions by the protons  H⁺ of water. Two  H⁺ are then reduced into H₂.

${\displaystyle {\ce {3 Fe(OH)2 -> Fe3O4 + 2 H2O + H2}}}$

In the Schikorr reaction, the two  H⁺ reduced into H₂ are these from two OH⁻ anions, then transformed into two oxide anions (O²⁻) directly incorporated into the magnetite crystal lattice while the water in excess is liberated as a reaction by-product.

Hydrogen produced by the serpentinization reaction is important because it can fuel microbial activity in the deep subsurface environment.

Hydrothermal vents and mud volcanoes

A white carbonate spire in the Lost City hydrothermal field

Deep sea hydrothermal vents located on serpentinite close to the axis of mid-ocean ridges generally resemble black smokers located on basalt, but emit complex hydrocarbon molecules. The Rainbow field of the Mid-Atlantic Ridge is an example of such hydrothermal vents. Serpentinization alone cannot provide the heat supply for these vents, which must be driven mostly by magmatism. However, the Lost City Hydrothermal Field, located off the axis of the Mid-Atlantic Ridge, may be driven solely by heat of serpentinization. Its vents are unlike black smokers, emitting relatively cool fluids (40 to 75 °C (104 to 167 °F)) that are highly alkaline, high in magnesium, and low in hydrogen sulfide. The vents build up very large chimneys, up to 60 meters (200 ft) in height, composed of carbonate minerals and brucite. Lush microbial communities are associated with the vents. Though the vents themselves are not composed of serpentinite, they are hosted in serpentinite estimated to have formed at a temperature of about 200 °C (392 °F).^[12] Sepiolite deposits on mid-ocean ridges may have formed through serpentinite-driven hydrothermal activity.^[13] However, geologists continue to debate whether serpentinization alone can account for the heat flux from the Lost City field.^[12]

The forearc of the Marianas subduction zone hosts large serpentinite mud volcanoes, which erupt serpentinite mud that rises through faults from the underlying serpentinized forearc mantle. Study of these mud volcanoes gives insights into subduction processes, and the high pH fluids emitted at the volcanoes support a microbial community.^[14][10]

Serpentinite thermal vents are a candidate for the environment in which life on Earth originated.^[14] Most of the chemical reactions necessary to synthesize acetyl-CoA, essential to basic biochemical pathways of life, take place during serpentinization.^[15] The sulfide-metal clusters that activate many enzymes resemble sulfide minerals formed during serpentinization.^[16]

Experimental drilling into the gabbro layer of oceanic crust near mid-ocean ridges has demonstrated the presence of a sparse population of hydrocarbon-degrading bacteria. These may feed on hydrocarbons produced by serpentinization of the underlying ultramafic rock.^[17][18]

Decorative stone in architecture and art

Drinking cups, evidences of serpentinite turning in Zöblitz

Serpentine group minerals have a Mohs hardness of 2.5 to 3.5, so serpentinite is easily carved.^[25] Grades of serpentinite higher in calcite, along with the verd antique (breccia form of serpentinite), have historically been used as decorative stones for their marble-like qualities. College Hall at the University of Pennsylvania, for example, is constructed out of serpentine. Popular sources in Europe before contact with the Americas were the mountainous Piedmont region of Italy and Larissa, Greece.^[26] Serpentinites are used in many ways in the arts and crafts. For example, the rock has been turned in Zöblitz in Saxony for several hundred years.^[27]

Carving stone tools, oil lamp-known as the Qulliq and Inuit sculpture

The Inuit and other indigenous people of the Arctic areas and less so of southern areas used the carved bowl shaped serpentinite qulliq or kudlik lamp with wick, to burn oil or fat to heat, make light and cook with. The Inuit made tools and more recently carvings of animals for commerce.^[28]

• 
  Magnetic serpentine walrus
• 
  Inuit Elder tending the Qulliq, a ceremonial oil lamp made of serpentinite.

Swiss ovenstone

A variety of chlorite talc schist associated with Alpine serpentinite is found in Val d'Anniviers, Switzerland and was used for making "ovenstones" (German: Ofenstein), a carved stone base beneath a cast iron stove.^[29]

Neutron shield in nuclear reactors

Serpentinite has a significant amount of bound water, hence it contains abundant hydrogen atoms able to slow down neutrons by elastic collision (neutron thermalization process). Because of this, serpentinite can be used as dry filler inside steel jackets in some designs of nuclear reactors. For example, in RBMK series, as at Chernobyl, it was used for top radiation shielding to protect operators from escaping neutrons.^[30] Serpentine can also be added as aggregate to special concrete used in nuclear reactor shielding to increase the concrete density (2.6 g/cm³ (0.094 lb/cu in)) and its neutron capture cross section.^[31][32]

CO₂ sequestration

Because it readily absorbs carbon dioxide, serpentinite may be of use for sequestering atmospheric carbon dioxide.^[33] To speed up the reaction, serpentinite may be reacted with carbon dioxide at elevated temperature in carbonation reactors. Carbon dioxide may also be reacted with alkaline mine waste from serpentine deposits, or carbon dioxide may be injected directly into underground serpentinite formations.^[34] Serpentinite may also be used as a source of magnesium in conjunction with electrolytic cells for CO₂ scrubbing.^[35]