Chrysotile

Hand Specimen identification: Fiberlike, asbestiform appearance is diagnostic (Figure 8). Chrysotile may be distinguished from most fibrous amphiboles by its greenish white color; com-pare Plates 3.4 and 3.7.

Chemical Composition : Mg6Si4O10(OH)8

Hardness : 3 to 5

Specific Gravity2.5 to 2.6

Cleavage/Fracture : none/uneven

Luster/Transparency : greasy, waxy/translucent

Color : variable white, greenish white

Streak : white

Optical Properties :

Crystallography : Monoclinic, a = 5.34, b = 9.25, c = 14.65, b = 93°, Z = 8; or orthorhombic, depending on polymorph.

Habit : Fibrous, asbestiform habit typifies chrysotile (Figure 8).

Structure and composition : Composition and structure are similar to those of antigorite, except that the mismatch in spacing of the octahedral and tetrahedral layers causes them to curl in one direction only, forming fibers.

Occurrence and associations : Occurrence and associations are the same as for antigorite. In many serpentine samples, chrysotile layers are separated by a fine-grained platy poly-morph called lizardite.

Varieties :

Related Minerals : Chrysotile has two polymorphs, lizardite and antig-orite. Greenalite, Fe3Si2O51OH24, the Fe equivalent of serpentine, has a different structure. Amosite and cro-cidolite, varieties of amphibole, are also asbestiform.