Geology Reference
In-Depth Information
Table 3.1.2
Minerals found in coal.
Mineral Group
Mineral
Composition
Occurrence
Clay
Illite
-
sericite
(K, H
3
O) (Al, Mg, Fe)
2
(Si, Al)
4
O
10
(OH)
2
˙
nH
2
O
dom
-
ab
Montmorillonite
Al
4
Si
4
O
10
(OH)
2
˙
nH
2
O
r
-
c
Kaolinite
Al
4
Si
4
O
10
(OH)
8
c
-
vc
Halloysite
Al
2
Si
2
O
5
(OH)
4
r
Iron disulfides
Pyrite
FeS
2
r
-
c
Marcasite
FeS
2
r
Melnikovite
FeS
2
r
Carbonates
Siderite
FeCO
3
c
-
vc
Ankerite
CaFe(CO
3
)
2
c
-
vc
Calcite
CaCO
3
c
-
vc
Dolomite
CaMg(CO
3
)
2
r
-
c
Oxides
Hematite
Fe
2
O
3
r
Magnetite
FeFe
2
O
4
vr
Rutile
TiO
2
vr
Hydroxides
Limonite
HFeO
2
r
-
c
Goethite
HFeO
2
r
Diaspore
HAlO
2
r
Sulfides/selenides
Sphalerite
ZnS
r
Galena
PbS
r
Chalcopyrite
CuFeS
2
vr
Pyrrhotite
FeS
vr
Clausthalite
PbSe
vr
Phosphates
Apatite
Ca
5
(PO
4
)
3
(F, Cl, OH)
r
Crandallite group
(Ba, Ca, Ce, Nd, Pb, Sr, Th)(Al, Fe)
3
[(P, As)O
4
]
2
(OH)
5
with or without H
2
O
r
Sulfates
Barite
BaSO
4
r
Gypsum
CaSO
4
˙
2H
2
O
r
Source
: Modified after Stach et al., 1982; other minerals are possible.
Note
: Chemical compositions are variable and may include trace elements.ab, abundant; dom, dominant; c, common; r, rare; vc, very common;
vr, very rare.
Microlithotypes
M
icrolithotypes (Table 3.1.3) are associations of macerals that occur in bands at least 50-
m thick. There are three
μ
main classes of microlithotypes:
(1) Monomaceral microlithotypes contain one maceral or maceral group, for example, liptite (dominated by
liptinite (L) macerals) or vitrite (dominated by vitrinite (V) macerals).
(2) Bimaceral microlithotypes are composed of macerals of two maceral groups, each accounting for
5%, for
example, clarite (dominated by vitrinite and liptinite) or durite (dominated by liptinite and inertinite (I)).
(3) Trimaceral microlithotypes are composed of macerals of three maceral groups, each accounting for at
least 5%, namely duroclarite (V
>
>
L or I), clarodurite (I
>
V or L), and vitrinertoliptite (L
>
V or I).
Associations of microlithotypes rich in mineral matter are called carbominerites. In carbominerites, the mineral
matter accounts for at least 20% (volume) in case of silicates or carbonates or 5% (volume) of sulfides.
Lithotypes
L
ithotypes are megascopically identified layers in coal seams (Figure 3.1.5). Lithotype variations in the coal reflect
changes in organic input and depositional conditions in the mire.
