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In Grand Canyon there are two side streams that carry heavy carbonate loads and deposit travertine along their lengths. The Little Colorado and Havasu Creek both rise from springs a few miles above the river and are separated by over one hundred river miles.

The white carbonate precipitate in each makes the light turquoise color of the water strikingly visible. What mineral in the water gives it the light turquoise color?

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The color of the water is determined by depth and mineral composition. Calcium carbonate is carried in the Little Colorado river water column and coats the river bottom. Calcium carbonate scatters white light (aka, looks white), so combined with water, which scatters blue light, a turquoise color is formed. When the water column is thin, white scattering of the calcium carbonate is more pronounced and the color of the water is lightened. In the deeper parts of the river, the color is a darker blue due to the smaller concentration of calcium carbonate (due to more volume of water) and the increased scattering of blue light through a thicker water column.

This blog has a great explanation.

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  • $\begingroup$ That is not correct. You can fill a white container with clear water a couple meters deep and the water will not appear blue because water scattering of short wavelength light is subtle to the human eye until depths reach about ten meters. Little Colorado water is bright blue at even a few centimeters depth. Also, the concentration of CaCO3 in Little Colorado water is uniform. It is at saturation regardless of depth. $\endgroup$ – Brian Sep 4 '15 at 18:19
  • $\begingroup$ I waded across the Little Colorado just above its confluence with the Colorado River on April 15 and it was milky white. I have been there previously when it appeared turquoise blue (and when it was in flood and running brown), but I have never seen such a pronounced opaque white color. The above explanation does make some sense, but I'm not sure what is meant by a "thin" water column. The river was running just at seasonal average on April 15 at 250cfs and 5.30 feet depth at the gauge. $\endgroup$ – user7975 Apr 26 '17 at 18:48

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