1. Serpentine Group
Presentation prepared by Oliver Boyd

2. Serpentine: A Phyllosilicate
Formula: Mg3Si2O5(OH)4
End Members: Lizardite, Chrysotile, and Antigorite

3. Serpentine: A Phyllosilicate

4. Serpentine: Structure
Member
Lizardite
Chrysotile
Antigorite
Crystal System
Triclinic
T – P31m H1 – P63cm
Monoclinic
A2/m
Monoclinic Pm or P2/m a
5.308
5.313
43.53 b
9.2
9.12
9.26 c
42.712
14.637
7.26 
90.0 
93.167
91.6  Z 12 4 16
Volume (Å3)
708.15
Density (kg/m3)
2658
2609
2526

5. Serpentine: Structure

6. Serpentine: Occurrence
Serpentine minerals commonly occur as alterations of magnesium silicates, especially olivine, pyroxene, and amphibole. The following is a possible reaction:
Mg2SiO4 + 3H2O Mg3Si2O5(OH)4 + Mg(OH)2
Associated with magnesite, chromite, and magnetite, it is found in both igneous and metamorphic rocks and may make up the entire rock mass. Chrysotile is the asbestiform variety of serpentine. It is extensively mined and is the primary asbestos mineral.

7. Serpentine: Occurrence
Fig. 4 from Angel et al The maximum thermal stability of hydrous phases in sediment (Ono, 1998), MORB basalt (Schmidt and Poli, 1999), and ultramafic harzburgite (Frost, 1999) bulk compositions. Positions of the –-, –- and -Pv + MW transformations for (Mg1.8Fe0.2)SiO4 are shown in gray (Ito and Takahashi, 1989; Katsura and Ito, 1989). An average mantle adiabat (ama), an estimate of the minimum temperature in a subducting slab (cs), and the antigorite breakdown curve (ant) are also shown (Jeanloz and Morris, 1986; Ulmer and Trommsdorff, 1995; Irifune et al., 1996; Stein and Stein, 1996).