Fig. 2.11 Biotite from a lahar deposit of Mt. Pinatubo. (a) Optical micrograph, (b) SEM image, (c)
EDX spectrum of the dashed area in (b), (d, e, and f) EDX spectrum-mimic graphs showing the
elemental compositions of the maximum, intermediate, and minimum Mg members of the biotite
series (112 samples) listed by Fleet (2003), (g) powder XRD pattern of the biotite particles, (h)
reference powder XRD pattern (Brindley and Brown 1980)
No feldspars
Na
Ca
K
Plagioclase
(Albite)
(Anorthite)
(Orthoclase)
Fig. 2.12 Simplified
triangle diagram showing
the K, Na, and Ca
compositions of natural
feldspars and their
end-members (orthoclase,
albite, and anorthite)
24
2 Primary Minerals