Microlithotype

The individual microconstituents in coal or macerals rarely occur by themselves but are mostly in association with each other. Such association of macerals is termed as microlithotype. Broadly, they are divided into three groups, namely, monomaceral, bimaceral, and trimaceral, based on whether a microlithotype contains macerals of one, two, or three maceral groups. All microlithotypes bear the suffix “ite” so as to distinguish them from macerals. An area of 50 × 50 μ is considered on the polished surface of coal perpendicular to the bedding plane for microlithotype analysis. Mono-, bi-, or trimaceral microlithotypes are classified as per the content of major and accessory macerals. For example, microlithotype vitrite must contain 95 % vitrinite. In addition to the maceral content, 20–60 % (vol) of silicate or carbonate minerals or 5–20 % (vol) sulfide minerals redefine the microlithotype as a carbominerite. The following table describes the classification of microlithotypes.

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