| Amesite | |
| Formula: | Mg2Al2SiO5(OH)4 |
| Imasymbol: | Ame[1] |
| Strunz: | 9.ED.15 |
| System: | Triclinic |
| Class: | Pedial (1) (same H-M symbol) |
| Symmetry: | C1 |
| Unit Cell: | a = 5.307(1), b = 9.195(2) c = 14.068(3) [Å] α = 90.09(2)° β = 90.25(2)°, γ = 89.96(2)°; Z = 4 |
| Color: | White, colorless, pink to lilac, pale green |
| Habit: | Crystals form as platy to tapering elongated pseudohexagonal prisms |
| Twinning: | Common as six-fold sector twins on and polysynthetic twins parallel to |
| Cleavage: | Perfect on |
| Tenacity: | Brittle |
| Mohs: | 2.5–3 |
| Luster: | Pearly |
| Refractive: | nα = 1.597 nβ = 1.599 nγ = 1.615 |
| Opticalprop: | Biaxial (+) |
| Birefringence: | δ = 0.018 |
| Streak: | White with pale green tint |
| Gravity: | 2.77 |
| Diaphaneity: | Transparent to translucent |
| Other: | Kaolinite-serpentine group |
| References: | [2] [3] [4] |
Amesite is a mineral with general formula of Mg2Al2SiO5(OH)4.[3]
Amesite crystallizes in the triclinic crystal system.[5] It contains three axes of unequal length, not at right angles.
It was first described in 1876 for an occurrence in the Chester Emery Mines, Chester, Hampden County, Massachusetts. It was named for mine owner James Ames.[4] [3] It occurs in an environment of low-grade metamorphism affecting rocks with high aluminium and magnesium content. It occurs associated with vesuvianite, chlorite, magnetite, rutile, diaspore, grossular, calcite, diopside and clinozoisite in various locations.[2]
Amesite is an uncommon silicate mineral which has been reported from a variety of locations worldwide.[3] Amesite has the first reported natural occurrence of the 6R polytype for a trioctahedral 1:1 layer silicate.[6]