Fig. 2: BSE image of early HMC cement in plant-only coal ball.
From: A marine origin of coal balls in the Midland and Illinois basins, USA
This plant-only coal ball is from the Williamson No. 3 Deposit, Williamson, Iowa, Pennsylvanian (late Atokan - early Desmoinesian; Midcontinent shelf). Columnar crystals of early HMC cement shown here in cross-section, appear speckled in the BSE image. Vuggy LMC (light grey calcite) surrounding the HMC polycrystals results from the diagenetic alteration of HMC. The small dark grey carbonates are non-stoichiometric dolomite crystals. HMC high-magnesium calcite, LMC low-magnesium calcite, V vug, Dolo non-stoichiometric dolomite. The scale is 30 µm. Image taken by Rachel Wells.
