page_title: Ringwoodite
section_title: Physical properties
hierarchical_section_title: Ringwoodite / Physical properties
context_page_description: Ringwoodite is a high-pressure phase of Mg₂SiO₄ formed at high temperatures and pressures of the Earth's mantle between 525 and 660 km depth. It may also contain iron and hydrogen. It is polymorphous with the olivine phase forsterite.
  Ringwoodite is notable for being able to contain hydroxide ions within its structure. In this case two hydroxide ions usually take the place of a magnesium ion and two oxide ions.
  Combined with evidence of its occurrence deep in the Earth's mantle, this suggests that there is from one to three times the world ocean's equivalent of water in the mantle transition zone from 410 to 660 km deep.
  This mineral was first identified in the Tenham meteorite in 1969, and is inferred to be present in large quantities in the Earth’s mantle.
  Ringwoodite was named after the Australian earth scientist Ted Ringwood, who studied polymorphic phase transitions in the common mantle minerals olivine and pyroxene at pressures equivalent to depths as great as about 600 km.
  Olivine, wadsleyite, and ringwoodite are polymorphs found in the upper mantle of the earth. At depths greater than about 660 km, other minerals, including some with the perovskite structure, are stable.
context_section_description: The physical properties of ringwoodite are affected by pressure and temperature. The calculated density value of ringwoodite is 3.90 g/cm³ for pure Mg₂SiO₄; 4.13 g/cm³ for (Mg0.91,Fe0.09)₂SiO₄ of pyrolitic mantle; and 4.85 g/cm³ for Fe₂SiO₄. It is an isotropic mineral with an index of refraction n = 1.768.
  The colour of ringwoodite varies between the meteorites, between different ringwoodite bearing aggregates, and even in one single aggregate. The ringwoodite aggregates can show every shade of blue, purple, grey and green, or have no colour at all.
  A closer look at coloured aggregates shows that the colour is not homogeneous, but seems to originate from something with a size similar to the ringwoodite crystallites.  In synthetic samples, pure Mg ringwoodite is colourless, whereas samples containing more than one mole percent Fe₂SiO₄ are deep blue in colour. The colour is thought to be due to Fe²⁺–Fe³⁺ charge transfer.
caption: Molar volume vs. pressure at room temperature for ahrensite γ-Fe2SiO4