Fig. 1. Hematite filaments and spheroids in NSB jasper-carbonate BIF.

(A) Transmitted light image of a bundles of pectinate-branching hematite filaments with undulations and tubes and co-occurring clusters of irregular ellipsoids. (B) Corresponding interpretive drawing showing straight filaments (blue lines), undulated or coiled filaments (red lines), tubes (orange lines), rosettes (purple circles), clusters of irregular ellipsoids (green ovals), and areas for other figure panels and videos. The four photos in inset show four examples of branching filament intersections in this structure. (C) Cluster of irregular ellipsoids inside a coarse quartz granule rimmed by two undulated filaments (red arrows). (D) Parallel-aligned hematite filaments and associated irregular ellipsoids. (E) Raman image showing a filament with coarse Fe²⁺-bearing hematite (yellow) and hematite (purple) (spectra shown in fig. S4N). (F) BSE image of a cross-sectioned undulated filament (shown in fig. S4K) with graphitic carbon (white arrows) associated with ferrous hematite (yellow contour) and quartz inclusions (blue arrows). (G) Histogram of the sizes of the irregular ellipsoids (average of major and minor axes).