28 March 2012

Hanksite and other wonders of Searles Lake

Posted by Callan Bentley

Playa lakes are features that develop in low-lying areas of enclosed basins. Because water carries dissolved ions into the lake basin but not out (the water leaves by evaporation), the lakes become quite salty. Sometimes they dry up, to become salt flats, or merely “playas.” Occasionally, there’s good stuff in these briney lowlands. That’s the case at Trona, California, on the shores of Searles Lake, a lake that is partially wet…

… and partially dried out into a massive salt flat:

What were we out here to see? Well, it’s always cool to walk out into wide open spaces, particularly with the crunch of salt under your boots, letting you know something fundamental about the hydrology of the area…

…Also, there were giant crystals of hanksite (KNa22(SO4)9(CO3)2Cl). This is the place where hanksite was first described, and where it is most common in the world:

There were also evaporating ponds that produced halite (NaCl):

Here’s a mostly-dissolved halite crystal with growth layers:

Salt flats with dessication cracks:

Up close, you can see the characteristic 120° angles at which these fractures meet, as well as the “teepee” structures that can form due to subsequent expansion:

Lastly, consider these two lovely crystals of sulfohalite (Na6(SO4)2FCl) that Erik found: