Lizardite

Lizardite is a mineral from the serpentine subgroup^[3] with formula Mg₃(Si₂O₅)(OH)₄, and the most common type of mineral in the subgroup.^[4] It is also a member of the kaolinite-serpentine group.^[5]

Lizardite
General
Category	Mineral
Formula (repeating unit)	Mg3(Si2O5)(OH)4[1]
IMA symbol	Lz[2]
Strunz classification	9.ED.15
Dana classification	71.01.2b.02
Crystal system	Trigonal
Identification
Color	Green, brown, light yellow to white
Mohs scale hardness	2.5
Luster	Resinous, waxy, greasy
Streak	White
Specific gravity	2.55

Lizardite may form a solid-solution series with the nickel-bearing népouite (pure end-member: Ni₃(Si₂O₅)(OH)₄). Intermediate compositions (Mg,Ni)₃(Si₂O₅)(OH)₄ are possible, with varying proportions of magnesium and nickel.^[6] However, the lizardite end-member is much more common than pure népouite, a relatively rare mineral most often formed by the alteration of ultramafic rocks.

Extremely fine-grained, scaly lizardite (also called orthoantigorite) comprises much of the serpentine present in serpentine marbles. It is triclinic, has one direction of perfect cleavage, and may be white, yellow or green. Lizardite is translucent and soft, and may be pseudomorphous after enstatite, olivine or pyroxene, in which case the name bastite is sometimes applied. Bastite may have a silky lustre.^[1]

Name

Lizardite was named by Eric James William Whittaker and Jack Zussman in 1955 after the place it was first reported, the Lizard Peninsula, (from the Cornish: An Lysardh) in southern Cornwall, England, United Kingdom.

Scyelite is a synonym of lizardite.^[1]

Characteristics

Chemistry

Antigorite and lizardite commonly coexist metastably;^[7]: 24 lizardite may also be able to turn into antigorite at over 350 degrees.^[8]: 712

Lizardite contains H₂O in excess of the nominal formula, as does chrysotile. It has a high amount of Fe₂O₃ and a low amount of FeO.^[9]: 8

One study found that lizardite has a high amount of SiO₂ and a low amount of Al₂O₃.^[10]: 193

Formation

Lizardite is commonly a result from the hydrothermal metamorphism or retrograde metamorphism of mafic minerals such as olivine, pyroxene or amphibole, in ultrabasic rocks.^[11]

Occurrence

Geological occurrence

Lizardite is commonly found in ophiolite^[12] and is often intergrown with brucite.^[9]: 8 It is also found with magnetite^[11] and the other serpentine minerals.^{[13]: 118–119}

Locations found

Canada

As of 1989, only a single specimen of lizardite had been found in Mont-Saint-Hilaire, Quebec where it may occur in altered pegmatites.^[14]: 184

United States

Lizardite can be found in the United States.^[15] In Pennsylvania It was discovered in the 1960s.^[16]: 55 With it being the most abundant mineral in Nottingham County Park.^[17]

In Minnesota it can be found on the north shore of Lake Superior.^[1]

In Montana, the Stillwater igneous complex is a prominent location for the mineral.^[15]

United Kingdom

Lizardite has a type locality at Lizard Peninsula, Cornwall, in the United Kingdom.^[1]

Scotland is a notable source of lizardite.^[18] Lizardite has been reported in Wales. At Holy Island, Anglesey lizardite has been found to be associated with antigorite.^[11]

South Africa

In the Frank Smith mine located in South Africa, lizardite was the dominant serpentine mineral.^[10]: 212

Orange lizardite has been found at the Wessels mine.^[19]

Other

It can also be found in Japan, Italy, and Australia.^[20]

References

1. Lizardite, Mindat.org
2. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
3. Allaby, Michael (2020-01-09). A Dictionary of Geology and Earth Sciences. Oxford University Press. ISBN 978-0-19-257570-8.
4. "Lizardite gemstone information". www.gemdat.org. Retrieved 2021-10-26.
5. Gaines, Richard V.; Skinner, H. Catherine W.; Foord, Eugene E.; Mason, Brian; Rosensweig, Abraham (1997). Dana's new mineralogy : the system of mineralogy of James Dwight Dana and Edward Salisbury Dana (8th, entirely rewritten and greatly enl. ed.). New York: Wiley. ISBN 978-0471193104.
6. Brindley, G.W.; Wan, Hsien-Ming (1975). "Compositions, structures, and thermal behavior of nickel-containing minerals in the lizardite-nepouite series". American Mineralogist. 60: 863–871. Retrieved 3 November 2021.
7. Alexander, Earl B.; Coleman, Robert G.; Keeler-Wolfe, Todd; Keeler-Wolfe, Senior Vegetation Ecologist Wildlife and Habitat Data Analysis Branch Todd; Harrison, Susan P. (2007-03-22). Serpentine Geoecology of Western North America: Geology, Soils, and Vegetation. Oxford University Press, USA. ISBN 978-0-19-516508-1.
8. Earth and Life Processes Discovered from Subseafloor Environments: A Decade of Science Achieved by the Integrated Ocean Drilling Program (IODP). Elsevier. 2014-12-03. ISBN 978-0-444-62611-0.
9. Roberts, B. A.; Proctor, J. (2012-12-06). The Ecology of Areas with Serpentinized Rocks: A World View. Springer Science & Business Media. ISBN 978-94-011-3722-5.
10. Deer, William Alexander; Howie, Robert Andrew; Zussman, J. (2009). Rock Forming Minerals: Layered Silicates Excluding Micas and Clay Minerals, Volume 3B. Geological Society of London. ISBN 978-1-86239-259-5.
11. "Mineral Database - Mineralogy of Wales". National Museum Wales. Retrieved 2021-10-26.
12. Laurora, Angela; Brigatti, Maria Franca; Maiferrari, Daniele; Galli, Ermanno; Rossi, Antonio; Ferrari, Massimo (2011). "The crystal chemistry of lizardite-1T from northern Apennines ophiolites near Modena, Italy" (PDF). The Canadian Mineralogist. 49 (4): 1045–1054. Bibcode:2011CaMin..49.1045L. doi:10.3749/canmin.49.4.1045. Retrieved 3 November 2021.
13. Pichler, Hans; Schmitt-Riegraf, Cornelia (2012-12-06). Rock-forming Minerals in Thin Section. Springer Science & Business Media. ISBN 978-94-009-1443-8.
14. Mandarino, Joseph Anthony; Anderson, Violet (1989-03-31). Monteregian Treasures: The Minerals of Mont Saint-Hilaire, Quebec. CUP Archive. ISBN 978-0-521-32632-2.
15. "Lizardite". National Gem Lab. 2017-03-14. Retrieved 2021-10-27.
16. Montgomery, Arthur (2008). Mineralogy of Pennsylvania 1922-1965: Supplementing and Updating Gordon's the Mineralogy of Pennsylvania (1922). Academy of Natural Sciences. ISBN 978-1-4223-1786-0.
17. Pazzaglia, Frank James (2006-01-01). Excursions in Geology and History: Field Trips in the Middle Atlantic States. Geological Society of America. p. 19. ISBN 978-0-8137-0008-3.
18. "Serpentine Value, Price, and Jewelry Information - Gem Society". International Gem Society. Retrieved 2021-10-27.
19. Rossman, George; Laurs, Brendan M. (2014). "Orange Lizardite from South Africa". Journal of Gemmology. 34 (2): 98–99. ISSN 1355-4565.
20. "Gemmology | Classification | Lizardite". www.nmnhs.com. Retrieved 2021-11-02.