The Rio Celeste - not a reaction

Atlas Obscura says it ever so simply and vaguely...

The river gets its coloration from a mixture of sulfur and calcium carbonate which are seeded into the water from the nearby volcano.

So does Neatorama...

large quantities of sulfur and calcium carbonate, which gives the river a beautiful blue tint

...and The Soul is Bone...

a vivid blue colour, the result of the chemical reaction( the result of sulphur and calcium carbonate mixing) generated by a mixture of minerals present in the volcanic massif

Of course, that chemical reaction isn't very well explained there, so I went a looking for some more detail. Here's what I found on Wikipedia...

The source of the river's distinctive turquoise color is not a due to a chemical species but to a physical phenomenon known as Mie scattering.^[3] Celeste River is fed by two colorless rivers, the Buenavista River and Sour Creek. Buenavista River carries a large concentration of aluminosilicate particles with a small diameter. Sour Creek, as its name implies, has a high acidity due to volcanic activity. When these two streams mix to form Celeste River, the drop in pH causes the aluminosilicate particles to aggregate and enlarge to a diameter of about 566 nm. These suspended particles produce Mie scattering which gives the river a strong turquoise color.

I clicked through citation #3 and found an article on PLOS One, the Public Library of Science, that has a heck of a lot more math and SEM images than I wanted to read through.

No matter what those data said, it's still a good reminder that it's a good choice to dig a little deeper when the explanation seems a bit too simple.

Otherwise, you may find yourself in murky waters.

Pretty, but murky waters...