Figure 2
From: Modern Iron Ooids of Hydrothermal Origin as a Proxy for Ancient Deposits
Scanning electron images of selected Panarea ooids. (a) Predominant ooidal morphologies. (b,c) Ooids with volcanic nuclei (pyroxene and plagioclase, respectively). (d) Cross section of a siliceous sponge spicula (dark grey) with goethite (light grey) filling the inner canal of the spicula and forming as well a thick external envelope made of concentric continuous laminae. (e) Coreless ooids. (f) Obsidian nucleus, partially uncovered by oxyhydroxides, revealing traces of chemical etching on the surface.
