Figure 4
From: A large explosive silicic eruption in the British Palaeogene Igneous Province
False colour BSE images of apatite crystals in Òigh-sgeir and Sgùrr of Eigg pitchstone deposits. (a) A plutonic inclusion in Òigh-sgeir pitchstone with feldspar (F), pyroxene (Px), apatite (green) and oxide (red-white). Note the various cuts of apatite crystals frequently show hollow interiors (skeletal growth). (b) Apatite in matrix glass (G), Òigh-sgeir pitchstone. Note the smaller euhedral apatites also. (c) Margin of a mineral clot in Òigh-sgeir pitchstone where an apatite crystal is becoming detached from an oxide (red) and is already largely surrounded by matrix glass. Note the rounded inner channel and the lobate embayment on the crystals lower right. (d) Dendritic skeletal apatite crystal (green) in glassy matrix in the Sgùrr of Eigg pitchstone. Also note the welded glass streaks below the ‘A’ in this image (also enlarged in inset), implying re-agglutinated fiamme as a result of rheomorphic flow in a hot and plastic condition (cf. ref.16). (e) Euhedral free-floating apatite in Sgùrr of Eigg pitchstone. (f) Free-floating apatite in pitchstone glass; Sgùrr of Eigg. The apatite shows euhedral outer crystals faces, but is breached and resorbed in its interior, indicating late-stage dissolution of the mineral.
