Page 99 - Atlas of Sedimentary Rocks Under The Microscope

Other sedimentary rocks: Carbonaceous rocks 216,217
C o a l s a n d c o a l b a l l s

Coals arc usually examined microscopically under high
power 111 reflected light using oil-immersion objectives
and therefore their detailed petrology is beyond the scope
of this hook. 216 is a thin section of a coal viewed in
transmitted light. The photograph shows durain. the dull
material in coal, composed of the more resistant plant
matter. The bright yellow fragments are spore-cases
distorted during compaction of the coal.
Coal balls are carbonate concretions formed before
compaction of the plant material in coal. They may be up
to a few tens of centimetres across and 217 shows a thin
section of part of one. The photograph shows that they
contain well-preserved cellular tissue of plants.

216: Coal Measures. Upper Carbonif erous. England;
magni/lwtion x 14. PPL.
217: Coal Measures. Upper Carboniferous. Lancashire.
Enxland: IIWKII{/iwtion x 9. PPL.

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