This specimen is an example of an alkali mineral that formed in an evaporite environment.

Evaporite: Alkalic Collection
Best known among several kinds of evaporite mineral deposits are the alkali minerals and the borate minerals. 

In the alkali lake, there develops a particularly high concentration of sodium, carbonate, calcium, and sulphate, together with chlorine, magnesium, potassium, and other highly soluble elements. As the lake waters evaporate, increasing concentration of these elements results in formation of various minerals, including common salt. West of Great Salt Lake, Utah, level miles of glistening salt can be seen in a famous deposit thick enough to support a local salt-processing industry.

In the less common borate lakes, several of which exist in California, Nevada, and Oregon, minerals composed primarily of hydrous borates are formed. Borax, the most familiar borate mineral is always found; in the United States, most of the commercial borax comes from the California and Nevada desert regions of “20 mule” fame. It is used mostly for cleaning.