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Scanning electron microscopy (SEM) of samples collected at Manleluag Spring National Park. (A) Terrace samples consist of rhomboid calcite crystals (ca), shown here precipitating on organic matter, likely a plant root (r). (B) Close-up of box in (A). (C) Putative cyanobacterial filament (fi) interbedded with calcite crystals (note hexagonal crystal, hex, in background). (D) Close-up of box in (C).
