Geology Reference
In-Depth Information
A
B
100
µ
m
Detrovitrinite
Collotelinite
Gelovitrinite
100
µ
m
C
Textinite
Corpogelinite
100
µ
m
Figure 3.1.1. (A) Gelovitrinite with liptodetrinite and inertodetrinite, (B) Detrovitrinite with fragments of
collotelinite and inertinite, (C) Textinite and corpohuminite.
Inorganic Matter in Coal
M
ineral matter (Figure 3.1.4) in coal could be of syngenetic origin (minerals incorporated or formed during peat
deposition or present in the inorganic compounds and organometallic complexes of the original plant material) or
epigenetic origin (formed postdepositionally during diagenesis, coalification, etc.).
The most abundant minerals in coal are clays and the most common are kaolinite, illite, montmorillonite, and
smectite. Carbonates are the next most common minerals in coal and they include calcite, siderite, ankerite, and
dolomite. Sulfides (e.g., pyrite, sphalerite, galena), silicates (e.g., quartz, zircon), and oxides (e.g., rutile) are also
found in coal and locally can occur in high concentrations. Table 3.1.2 (from Stach et al., 1982; Taylor et al., 1998)
lists some of the minerals identified in coal and their approximate abundance. Texturally, minerals may occur in
thin layers, as fillings of cleats and fractures in coal, as fillings of cell lumens in macerals, or intimately associated
with macerals or other minerals. Minerals such as siderite or pyrite can also replace cell walls. Minerals can also
occur finely dispersed within the coal matrix.
The content of mineral matter in coal is often proxied by ash yield. However, there are important differences
between mineral matter content and ash yield. Ash yield, as determined for the proximate and ultimate analyses,
results from the combustion of organic fraction and minerals and, therefore, presents lower quantity than mineral
