silicate mineral
Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust.
In mineralogy, silica (silicon dioxide, ) is usually consid ...
that can be compared to amphiboles, micas, and jimthompsonite. Its chemical formula is . Chesterite is named after
Chester, Vermont
Chester is a town in Windsor County, Vermont, United States. The population was 3,005 at the 2020 census.
History
The town was originally chartered by New Hampshire Governor Benning Wentworth as Flamstead in 1754. The terms of the charter were n ...
, where it was first described in 1977.Konishi, Hiromi, Reijo, Alviola, and Buseck, Peter R. (2004) 2111 biopyribole intermediate between pyroxene and amphibole: Artifact or natural product? American Mineralogist, 89, 15-19. 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.Wyckoff, R.W.G. (1968) Crystal Structures (Second edition). 310-314 p. University of Arizona, Tucson, Arizona. 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
Ultramafic rocks (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are igneous and meta-igneous rocks with a very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are composed ...
rocks.
A
polytype
In materials science, polymorphism describes the existence of a solid material in more than one form or crystal structure. Polymorphism is a form of isomerism. Any crystalline material can exhibit the phenomenon. Allotropy refers to polymorphism ...
of chesterite could be
anthophyllite
Anthophyllite is an orthorhombic amphibole mineral: ☐Mg2Mg5Si8O22(OH)2 (☐ is for a vacancy, a point defect in the crystal structure), magnesium iron inosilicate hydroxide. Anthophyllite is polymorphic with cummingtonite. Some forms of antho ...
, 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.