Environmental Engineering Reference
In-Depth Information
TABLE 5.11
Classification of Common Metamorphic Rocks
Fabric
Texture
Foliated
Massive
Coarse
Gneiss
Metaconglomerate
Amphibolite
Granite gneiss (imperfect foliations)
Medium
Schist (mica, chlorite, etc.)
Quartzite
Marble
Serpentinite
Soapstone
Fine to microscopic
Phyllite
Hornfels
Slate
Other forms
Migmatite: Complex composite rocks: intermixtures of metamorphic and
igneous rocks
Mylonites: Formed by intense mechanical metamorphism: show strong lam
inations, but original mineral constituents and fabric crushed
and pulverized. Formed by differential shearing movement
between beds
Banded or lenticular as shown in
Figure 5.5.
●
Schistose as shown in
Figure 5.6.
●
Slaty cleavage as shown in
Figure 6.35.
●
Metamorphic Derivatives of Igneous and Sedimentary Rocks
The general derivatives are summarized in
Table 5.12.
It is seen that some metamorphic
rocks can be derived from a large number of other rock types, whereas a few are charac-
teristic of a single other rock type.
Characteristics
Photos of some of the more common metamorphic rocks are given as Plates 5.20 to 5.28.
Characteristics of metamorphic rocks with foliate fabric are summarized in
Table 5.13
and
those with massive or other fabric are summarized in
Table 5.14.
FIGURE 5.5
Banding in the highly foliated Fordham gneiss, New York City (photo near natural scale).
