Cordierite

Name and discovery

Cordierite, which was discovered in 1813, in specimens from Níjar, Almería, Spain, is named after the French geologist Louis Cordier (1777–1861).

Occurrence

Cordierite typically occurs in contact or regional metamorphism of pelitic rocks. It is especially common in hornfels produced by contact metamorphism of pelitic rocks. Two common metamorphic mineral assemblages include sillimanite-cordierite-spinel and cordierite-spinel-plagioclase-orthopyroxene. Other associated minerals include garnet (cordierite-garnet-sillimanite gneisses) and anthophyllite. Cordierite also occurs in some granites, pegmatites, and norites in gabbroic magmas. Alteration products include mica, chlorite, and talc. Cordierite occurs, for example, in the granite contact zone at Geevor Tin Mine in Cornwall.

Commercial use

Catalytic converters are commonly made from ceramics containing a large proportion of synthetic cordierite. The manufacturing process deliberately aligns the cordierite crystals to make use of the very low thermal expansion along one axis. This prevents thermal shock cracking from taking place when the catalytic converter is used.

Gem variety

As the transparent variety iolite, it is often used as a gemstone. The name "iolite" comes from the Greek word for violet. Another old name is dichroite, a Greek word meaning "two-colored rock", a reference to cordierite's strong pleochroism. It has also been called "water-sapphire" and "Vikings' Compass" because of its usefulness in determining the direction of the sun on overcast days, the Vikings having used it for this purpose.{{cite book |trans-title=La bionique: Quand la science imite la Nature | orig-year = Published in French in 2008

Gem quality iolite varies in color from sapphire blue to blue violet to yellowish gray to light blue as the light angle changes. Iolite is sometimes used as an inexpensive substitute for sapphire. It is much softer than sapphires and is abundantly found in Australia (Northern Territory), Brazil, Burma, Canada (Yellowknife area of the Northwest Territories), India, Madagascar, Namibia, Sri Lanka, Tanzania and the United States (Connecticut). The largest iolite crystal found weighed more than 24,000 carats (4,800g), and was discovered in Wyoming, US. File:Cordierite.jpg|Left: rough specimen showing dichroism; right: cut stone File:Iolite.JPG|Facet cut iolite gemstone File:Cordierite_pléochroïsme.jpg|Pleochroism of cordierite

Another name for blue iolite is steinheilite, after Fabian Steinheil, the Russian military governor of Finland who observed that it was a different mineral from quartz. Praseolite is another iolite variety which results from heat treatment. It should not be confused with prasiolite.

Applications

Cordierite is used in manufacturing kiln furniture for its impressive thermal shock resistance, which allows it to withstand rapid temperature changes without cracking. It is also employed to produce insulation equipment and electric heating elements in fuses, thermostats, and lighting technology.

In the automotive industry, cordierite is used in catalytic converters due to its excellent thermal stability and low thermal expansion. It forms the honeycomb substrates within the converters, which support the catalytic coating that reduces harmful emissions.

References

| editor1-last = Cybulski|editor1-first= Andrzej | editor2-last = Moulijn|editor2-first= Jacob A. |access-date = March 25, 2009 |archive-url = https://web.archive.org/web/20120427025601/http://www2.gi.alaska.edu/ScienceForum/ASF8/865.html |archive-date = April 27, 2012 |url-status = dead

References

1. Warr, L.N.. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine.
2. http://webmineral.com/data/Cordierite.shtml Webmineral data
3. [http://www.topix.com/city/casper-wy/2011/09/wyoming-is-most-gemstone-rich-state-in-us Topix Local News: Casper, WY, ''Wyoming is Most Gemstone-Rich State in US,'' Sept. 13, 2011]
4. Sowerby, James. (1811). "Exotic mineralogy: or, Coloured figures of foreign minerals: as a supplement to British mineralogy". B. Meredith.
5. "Prasiolite". Amethyst Galleries' Mineral Gallery.
6. {{cite patent
7. Hegbom, Thor. (1997). "Integrating Electrical Heating Elements in Product Design". CRC Press.
8. (2024). "Developing thermal insulation cement-based mortars with recycled aggregate in accordance with net zero principles". Science of Sintering.
9. (Aug 8, 2024). "An Introduction to Cordierite Ceramic".
10. (2004). "Cordierite as catalyst support for cobalt and manganese oxides in oxidation–reduction reactions". Applied Catalysis A: General.
11. (1985). "Manual of Mineralogy". John Wiley and Sons. link