|
Serpentine
|
| Hydrous Magnesium Silicate |
|
Property
|
Value
|
Comments
|
| Formula |
Mg3Si2O5(OH)4 |
3 types: chrysotile, lizardite, and antigorite |
| Crystal
System |
Monoclinic |
Beta = 93° |
| Crystal
Habit |
Crysotile: Fibrous, elongated, and parallel
to crystallographic axis a Lizardite and antigorite: flat, tabular
crystals |
A mesh-like texture can be viewed with polarized
light.
|
| Cleavage |
Chrysotile: fibrous
Lizardite: basal cleavage
Antigortie: perfect {001} |
|
| Color/Pleochroism |
Green in thin section |
|
| Optic
Sign |
Biaxial (-) |
|
| 2V |
highly variable, may be sensibly uniaxial |
|
| Optic
Orientation |
Slow ray vibration direction is typically
parallel to the length of fibers in chrysotile -parallel extinction
Antigorite -Optic plane is perp or parallel to
(010). X=c, Y=b, Z=a or X=c, Y=a, Z=b |
|
Refractive
Indices
alpha =
beta =
gamma = |
1.529-1.595
1.530-1.603
1.537-1.604 |
|
| Max
Birefringence |
.001-.010 |
first order colors |
| Elongation |
parallel to crystallographic axis a |
|
| Extinction |
Straight on fibres, cleavage or crystal
edge. Chrysotile is length-slow |
|
| Dispersion |
r > v or r<v |
|
| Distinguishing
Features |
With the exception of cross-fibers of chrystolite
in veins, the varietites of serpentine cannot be distinguished without
X-ray diffraction or other techniques. |
| Occurrence |
Commonly formed by hydrothermal alteration of
mafic and ultramafic rocks- peridotite and pyroxenite. These
contain olivine and pyroxene. Associated minerals :talc, calcite,
brucite, chlorite, and chromite. Also can be found in contact
metamorphosed carbonate rocks, associated with calcite, forsteritre,
dolomite, magnesite, and calc-silicate. |
| Editors |
Emilie Flemer (01), Jennifer Unis (01),
Rebecca-Ellen Farrell (03), Liz Hogan (04) |
