At Shiqiang, China, there are spring towers, up to 4 m high and 3 m in diameter, that are formed of porous, gray to orange to brown, bedded limestones that have a multistage diagenetic history. The walls of many cavities in these limestones are covered with hypocoatings and/or needle-fiber calcite (NFC) that formed during the last stage of diagenesis. Where present, the hypocoatings are, similar to 10 mu m thick, appear homogeneous, and typically lie under the NFC mats. The NFC is divided into nanofibers (rods, < 1 mu m long, 75-100 nm diameter), composite fibers (bundles of 2 to 16 rods, each rod 300-400 nm in diameter, up to 25 mu m wide and 100 mu m long), pyramid fibers (pyramid shape with 4 to 6 sides, up to 25 wide at base, tapering to point, up to 100 mm long), and ribbon fibers (blade shape, 2-4 mu m wide similar to 1 mu m thick, up to 100 mu m long). Many crystals are highly ornate with epitaxial overgrowths that display elements of skeletal and/or dendritic growth. The wall-covering NFC mats are formed of one crystal type or any combination of different crystal types, with or without epitaxial overgrowths.
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