This silica sinter is growing in the highly acidic water of Lake Rotokawa, near Taupō. The needle-like silica growths are called spicules, and the green coating is the alga Cyanidium, which is able to live in hot, acidic conditions.
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GNS Science, Extremophile photo collection
Photograph by Bruce Mountain
Permission of GNS Science must be obtained before any use of this image.