Iddingsite is a microcrystalline rock that is derived from alteration of olivine. It is usually studied as a mineral, and consists of a mixture of remnant olivine, clay minerals, iron oxides, and ferrihydrites. Debates over iddingsite's non-definite crystal structure caused it to be de-listed as an official mineral by the IMA; thus, it is properly referred to as a rock.
Iddingsite forms from the weathering of basalt in the presence of liquid water and can be described[by whom?] as a phenocryst, i.e. it has macroscopically visible crystals in a fine-grained groundmass of a porphyritic rock. It is a pseudomorph that has a composition that is constantly transforming from the original olivine, passing through many stages of structural and chemical change to create a fully altered iddingsite.
Because iddingsite is constantly transforming it does not have a definite structure or a definite chemical composition. The chemical formula for iddingsite has been approximated as MgO * Fe2O3 * 3SiO2 * 4 H2O [1] where MgO can be substituted by CaO. The geologic occurrence of iddingsite is limited to extrusive or subvolcanic rocks that are formed by injection of magma near the surface. It is absent from deep-seated rocks and is found on meteorites. As it has been found on Martian meteorites, its ages have been calculated to obtain absolute ages when liquid water was at or near the surface of Mars.
It was named after Joseph P. Iddings, an American petrologist. [1]
^ abIddingsite, Mindat.org, retrieved March 25, 2019
Iddingsite is a microcrystalline rock that is derived from alteration of olivine. It is usually studied as a mineral, and consists of a mixture of remnant...
the surface according to the Goldich dissolution series. It alters into iddingsite (a combination of clay minerals, iron oxides and ferrihydrite) readily...
yellow to dark green; this is because olivine is easily weathered to iddingsite. While green and yellow are the most common colors, peridotitic rocks...
Institute of Polar Research reported in 2003 that the meteorite contains iddingsite, which forms from the weathering of basalt in the presence of liquid water...
Cohen, B. A.; Grier, J. A.; Li, B.; Olson, E. K. (2000). "Noble Gases in Iddingsite from the Lafayette meteorite: Evidence for Liquid water on Mars in the...
pahoehoe, with considerable concentrations of olivine (weathering to iddingsite) and plagioclase. Large amounts of gypsum can be found coating rocks near...
clinopyroxene, olivine, plagioclase and titanomagnetite, with secondary calcite, iddingsite, serpentine and zeolite. Based on compositional differences, the volcanic...
crusts cover the summit plateau. Weathering of volcanic rocks has produced iddingsite and palagonite, with calcite, chlorite and phyllipsite. Based on argon-argon...
clinopyroxene, olivine, and plagioclase, and further contain calcite, clay, iddingsite, and pyroxene. Aside from one rhyolite they are classified as an ocean...
of completely pseudomorphosed olivine (replaced by antigorite, reddish iddingsite, Mg-chlorite and magnetite), whereas the light bands consist of tremolite...
The basalt is distinctive for its olivine content (typically altered to iddingsite) and its diktytaxitic texture, in which the basalt contains microscopic...
of labradorite with olivine phenocrysts that have been transformed to iddingsite. The Boring Lava reaches thicknesses of more than 400 feet (120 m). Boring...
Wadhwa, and L. B. Williams. 2008. The boron isotopic composition of Nakhla iddingsite, paper presented at 39th Lunar and Planetary Science Conference, League...
olivine ranging from 2–5%, typically occurring in an altered form as iddingsite. For the vesicular andesite, up to 15% of phenocrysts are olivine, augite...
and basanite suites. The flows contain phenocrysts of clinopyroxene, iddingsite, olivine, plagioclase and sometimes spinel. Lava flows are covered by...
of these rocks other than a few instances of alteration of olivine to iddingsite. All the rocks in the area show a normal magnetic polarity, indicating...
Alteration has produced analcime, ankerite, calcite, clay, hematite, iddingsite, pyrite, quartz, saponite, serpentine and zeolite. The basalts represent...
this has given rise to analcime, augite, calcite, clay, clinoptilolite, iddingsite, ilmenite, labradorite, magnetite iron oxides and talc. Carbonates are...
Alteration of the original material has formed calcite, chlorite, clay, iddingsite, montmorillonite, zeolite, and a mineral that could be celadonite. Volcanogenic...
or upper crust. Beyond the Basanites, the overall lithology includes Iddingsite, Augite, Serpentinite, Magnetite, Orthoclase, Plagioclase, Olivine, Chlorite...
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