Chesterite

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title: "Chesterite" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["inosilicates", "orthorhombic-minerals", "minerals-in-space-group-36"] description: "Silicate mineral" topic_path: "general/inosilicates" source: "https://en.wikipedia.org/wiki/Chesterite" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Silicate mineral ::

::data[format=table title="Infobox mineral"]

Field	Value
name	Chesterite
image	Chesterit-chains.png
caption	Chesterite structure
category	Inosilicates (multiple chains)
formula
IMAsymbol	Chs
molweight	2,074.96 g/mol
strunz	9.DF.05
system	Orthorhombic
class	Pyramidal (mm2)
(same H-M symbol)
symmetry	A21ma
unit cell	a = 18.61 Å, b = 45.3 Å,
c = 5.29 Å, V = 4,459.64 Å3; Z = 4
color	Colorless, pink, brown
cleavage	(110) perfect
mohs	2-2.5
luster	Silky - pearly
refractive	α=1.617, β=1.632, γ=1.64
opticalprop	Biaxial negative
2V	70°
birefringence	δ = 0.023
streak	white
gravity	3.23
diaphaneity	transparent
pleochroism	weak, pink-brown
references
::

| name = Chesterite | image = Chesterit-chains.png | caption = Chesterite structure | category = Inosilicates (multiple chains) | formula = | IMAsymbol=Chs | molweight = 2,074.96 g/mol | strunz = 9.DF.05 | system = Orthorhombic | class = Pyramidal (mm2) (same H-M symbol) | symmetry = A21ma | unit cell = a = 18.61 Å, b = 45.3 Å, c = 5.29 Å, V = 4,459.64 Å3; Z = 4 | color = Colorless, pink, brown | cleavage = (110) perfect | mohs = 2-2.5 | luster = Silky - pearly | refractive = α=1.617, β=1.632, γ=1.64 | opticalprop = Biaxial negative | 2V = 70° | birefringence = δ = 0.023 | streak = white | gravity = 3.23 | diaphaneity = transparent | pleochroism = weak, pink-brown | references = Chesterite is a rare silicate mineral that can be compared to amphiboles, micas, and jimthompsonite. The specific geologic setting within its origin is the Carleton talc quarry in Chester, Vermont.

Chesterite has an orthorhombic crystal structure, which means it has three crystallographic axes of unequal length. All of the axes are perpendicular to each other. The stacking sequence for chesterite, which is found in micas, is very similar to orthopyroxenes and orthoamphiboles. Chesterite is an anisotropic mineral; therefore, it allows light to travel through it at different velocities when viewed at different angles. Chesterite is usually found in thin sheets within ultramafic rocks.

A polytype of chesterite could be anthophyllite, which has a similar crystal structure. Chesterite is used for research on stacking formations and symmetry point groups that could be possible polymorphs or polysomes of the amphibole-anthophyllite groups. Chesterite has no direct usage, but some geologists or scientists generally classify it under the amphibole-anthophyllite group.

References

References

1. Warr, L.N.. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine.
2. [https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Chesterite Mineralienatlas]
3. Ralph, Joylon and Ida, Chau. "Chesterite." http://www.mindat.org/min-997.html.
4. "Chesterite Mineral Data." http://webmineral.com/data/Chesterite.shtml. Accessed 3 November 2010.
5. Veblen, D.R. and Burnham, C.W. (1978) New biopyriboles from Chester, Vermont: II. The crystal chemistry of jimthompsonite, clinojimthompsonite, and Chesterite, and the amphibole-mica reaction. American Mineralogist, 63, 1053-1073.
6. Its chemical formula is {{chem. (Mg. ,Fe). 17. Si. 20. O. 54. (O. H)
7. Wyckoff, R.W.G. (1968) Crystal Structures (Second edition). 310-314 p. University of Arizona, Tucson, Arizona.

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