Chemistry Reference
In-Depth Information
Figure 1.8
Structure of the silicates.
(pyroxenes, wollastonite, aenigmatite) and double chains: (amphiboles,
astrophyllite);
tetraedra forming two planar sheets (
phyllosilicates
or sheet silicates):
mica group, chlorite group, serpentine, talc, stilpnomelane, clay miner-
als, prehnite,
apophyllite
;
tetraedres forming a tri-dimensional framework (
tectosilicates
or frame-
work silicates): quartz, feldspars, feldspathoids, analcime, scapolite
group,
zeolite group.
1.3
FACTORS OF OCCURRENCE OF MINERALS
The occurrence of minerals in a rock depends on physical and chemical factors.
1.3.1 Physical factors
Physical factors are conditions imposed from the outside during the for-
mation the rock: temperature, pressure (lithostatic pressure that depends
on the depth and directional pressures) and fluid pressure. These factors,
pressure on the rock and fluid pressure, are more or less independents. It is
