5) Clay minerals and Evaporites                                                     G 232

Phyllosilicates (clay mineral group)

kaolinite

Al phyllosilicate (member of kaolinite-serpentine group)

1) secondary mineral forming after aluminous silicates

quartz and other minerals resistant to alteration

(illite)

K phyllosilicate

1) weathering and diagenetic environment

other clay minerals and quartz

"Illite" refers to a group of mica-clay minerals of the general formula (K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,H2O];

some mineralogists classify illite minerals as belonging to the illite group.

montmorillonite

Ca, Na, Al, Mg phyllosilicate (member of smectite group)

1) secondary mineral forming after aluminous silicates

other clay minerals and quartz

Sulfates

 

 

 

anhydrite

CaSO4 

1) evaporite, 2) secondary, precipitated from groundwater, 3) hydrothermal veins and hot springs

gypsum, halite, sulfur, calcite, dolomite

gypsum

CaSO4 • 2H2O

1) evaporites, 2) deposited by groundwater in sedimentary rocks, 3) alteration product in ore deposits, 4) pneumatolitic around fumaroles

halite, sylvite, anhydrite, calcite, clay minerals, and many others

Halides

 

 

 

halite

NaCl

1) salt flats/evaporites

gypsum, calcite, sylvite, anhydrite, sulfur, clay minerals

sylvite

KCl

1) salt flats/evaporites

gypsum, calcite, sylvite, anhydrite, sulfur, clay minerals