Minerals
Minerals are an inherent part of coal and, by extension, Dispersed Organic Matter (DOM). These minerals can be transported into the basin by water or wind (known as detrital minerals) or formed within the basin itself (known as authigenic minerals).
The way minerals occur in relation to organic matter provides valuable insights into their interactions. Minerals can be dispersed within the organic matter matrix, found as nodules (e.g., siderite) or framboids (e.g., pyrite), or occur by infilling the cell lumina of certain macerals or fractures. The modes of occurrence of minerals are often linked to mineral paragenesis, which refers to the sequence and conditions under which minerals form.
The degree of intimacy between organic matter and minerals frequently determines the beneficiation process and the potential uses of coal. Additionally, the type and grain size of minerals in source rocks influence properties like permeability and porosity, which significantly impact the extraction of oil and gas. Minerals can also aid in maturation studies, such as evaluating the degree of crystallinity in certain clays.

Fusinite (Fu) maceral with cell lumina filled with kaolinite (Kao), ankerite (Ank) and chalcopyrite (Chpy) with galena (G) exudations. Rangal Coal Measures, Bowen Basin. SEM image in BSE mode.

Fine-grained matrix intermixed with organic matter (OM), probably lamalginite or bituminite. Foraminifera (Foram) tests are filled with kaolinite (Kao), solid bitumen (SB) and pyrite (Py) framboids. Toolebuc Formation, Eromanga Basin. SEM image in BSE mode.

Mineralogical mapping using QEMSCAN. Fractures filled with carbonates and clays. Quartz grains dispersed in mineral matter-rich layers. Fort Copper Coal Measures, Bowen Basin.

Siderite nodule. Moranbah Coal Measures, Bowen Basin. Photomicrographs in reflected white light (left) and fluorescent mode (right).