Amesite - Encyclopedia
Class : Silicates
Subclass : Phyllosilicates
Crystal System : Triclinic
Chemistry : Mg2AlSiAlO5(OH)4
Rarity : Rare
Amesite is a phyllosilicate of the serpentine group, usually pale green in color, turning pink and purplish in common chrome varieties. It owes its name to James Ames, owner of the Chester (Massachusetts) mines where it was discovered. Its crystals are pseudo-hexagonal lamellae and columnar prisms, constantly twinned, not exceeding a few millimeters. Amesite occurs mainly in foliated aggregates. It is an alteration mineral that can form in different contexts : calcium metasomatosis of granite, skarns, serpentinization of chrome dunites, etc... It is a mineral that has no particular use and remains little known to collectors.
Amesite in the World
Amesite in France
Twinning and special crystallizations
At right, an enlarged Robert Meyer image of amesite star-twinned crystals from Cerro Sapo, Ayopaya Province, Cochabamba, Bolivia. Specimen donated by Alfredo Petrov to the Seattle Mineral Market. The field width is 1.8 mm.
Fakes and scams
Hardness : 2.5 to 3
Density : 2.77 to 2.78
Fracture : Micaceous
Streak : White
TP : Translucent to transparent
IR : 1.596 to 1.616
Birefringence : 0.018 to 0.019
Optical character : Biaxial +
Pleochroism : Visible
Fluorescence : None
Solubility : None
Magnetism : None
Radioactivity : None