Figure 5. Field occurrences and hand specimens of Microfacies 1 sinter. (1) Overview of Microfacies 1 represented by a sulphur-emitting vents (84°C) around which subaerial sinter forms (red arrows). White-grey and orange deposits to the left and right belong to Microfacies 2 and 4, respectively. Green microbial mats form where water cools to <52.5°C. Note copious steam emission around sulphur discharging vent. Bar represents ~1.5 m. (2) Cup-shaped sinter (grey rim) depositing on the surface of a pumice clast. Spicules formed within a cavity on the uppermost side of the rim (red arrow). Bar represents 3 cm. (3) Ridge-shaped sinter on a pumice clast. Bar represents 3.5 cm. (4) Close-up of the lower portion of a Microfacies 1 sinter deposit. Multiple flat siliceous layers (yellow arrows) exhibit an irregular, gnarled surface texture. Isolated patches of silica (red arrows) also occur. (5) Vertical section through sinter and pumice substratum. Note the alternating light brown and light grey laminae. (6) Thin-section micrograph showing microspicules (red arrows) along the length of a brown lamina. Laminae become increasingly more convex upwards.