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Formula: Mg2Al(AlSiO5)(OH)4
Phyllosilicate (sheet silicate), serpentine subgroup
Crystal System: Triclinic
Specific gravity: 2.77 to 2.78 measured, 2.7 calculated
Hardness: 2½ to 3
Streak: White with very pale green tint
Colour: Originally pale greyish blue-green, also white, colourless, pale green, pink to lilac (chromian)
Environments
Amesite is a product of low-grade metamorphism of rocks rich in aluminium and manganese (Webmin). It is found with
clinochlore and magnetite, sometimes with
grossular, diopside,
calcite and clinozoisite, and occasionally with
margarite; it occurs rarely as an alteration product of
cancrinite
(Dana).
At the Pensacola Mountains, Antarctica, amesite is associated with vesuvianite and
chlorite
(HOM).
At Mine Lac d'Amiante (Lake Asbestos Mine; "LAB Mine"; "Black Lake Mine"), Saint-Joseph-de-Coleraine, Les Appalaches
RCM, Chaudière-Appalaches, Quebec, Canada, iron-rich amesite is found in a metasomatically altered
granite sheet emplaced in
serpentinite. The amesite is associated with a
rodingite assemblage
(grossular +
calcite +/- diopside +/-
clinozoisite) that has replaced the
primary minerals of the
granite. The Quebec amesite occurs as subhedral grains 200 to
600 microns in diameter that have a tabular habit. It formed during hydrothermal alteration of
granite in serpentinite
at the same low P-T conditions that prevailed during the formation of the
rodingite suite and the
chrysotile
asbestos in the serpentinite
(CM 22.3.437–442).
At Mount Sobotka, lower Silesia, Poland, amesite occurs with a variety of chlorite in vesicles in
rock fragments in the soils derived from a serpentinite
(AM 76.647-652).
At the type locality, the Chester Emery Mines, Chester, Hampden county, Massachusetts, USA, amesite occurs in an
emery deposit associated with
rutile, magnetite,
diaspore, clinochlore (Mindat, HOM) and
chamosite
(AM 29.422-430).
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