Illite
| Illite | ||
|---|---|---|
Specific gravity 2.6–2.9 | | |
| Optical properties | Biaxial (−) | |
| Refractive index | nα = 1.535 – 1.570 nβ = 1.555 – 1.600 nγ = 1.565 – 1.605 | |
| References | [2][3][4] | |
Illite, also called hydromica or hydromuscovite,
The cation-exchange capacity (CEC) of illite is smaller than that of smectite but higher than that of kaolinite, typically around 20 – 30 meq/100 g.
Illite was first described for occurrences in the Maquoketa shale in Calhoun County, Illinois, US, in 1937. The name was derived from its type location in Illinois.[2]
Brammallite is a sodium rich analogue. Avalite is a chromium bearing variety which has been described from Mt. Avala, Belgrade, Serbia.[8]
Zipao 'jade' is an ornamental form of illite showing bands of red-purple and pale yellow-green. It may be carved into pendants and other ornaments.
Illite crystallinity
The crystallinity of illite has been used as an indicator of metamorphic grade in clay-bearing rocks metamorphosed under conditions between diagenesis and low-grade metamorphism.[9] With increasing temperature, illite is thought to undergo a transformation into muscovite.[10]
References
- Mitchell JK (1993). "Ch. 3: Soil Mineralogy". Fundamentals of soil behavior (2nd ed.). New York: John Wiley and Sons, Inc. p. 32. ISBN 9780471463023.
- S2CID 235729616.
- ^ a b "Illite: Mineral information, data and localities". www.mindat.org. Retrieved 3 Apr 2019.
- ^ a b "Illite Mineral Data". webmineral.com. Retrieved 3 Apr 2019.
- S2CID 62881038.
- ^ USGSCoastal and Marine Geology Program. Retrieved 3 Apr 2019.
- ^ "Hydromuscovite: Mineral information, data and localities". www.mindat.org. Retrieved 2023-08-27.
- ISSN 0144-1485.
- ^ "Avalite: Mineral information, data and localities". www.mindat.org. Retrieved 3 Apr 2019.
- ISBN 9780632047567.
- .
External links
Media related to Illite at Wikimedia Commons
